A number of science educators feel that the computer simulation offers tremendous potential for the enhancement of the teaching and learning science concept. Wells & Berger (1986), Akpan & Andre (1999). Switzer and White (1984) discuss the place of the computer simulation in the social science classroom. According to these authors the computer simulation, as with any technology, the ultimate objective of its use in the classroom is to enhance learning. In addition the simulation's ability to provide opportunities for learners to develop skills in problem identification, seeking, organizing, analyzing, evaluating, and communication information. Ellis (1984), Marks (1982), Nakleh (1983), Switzer and White (1984) and Waugh (1984) would all support the fact that "It is in the area of simulations that computers have the potential to deal with higher learning outcomes in a way not previously possible inside the science classroom." Gagne, Wager and Rojas (1981) indicate that simulations help students to identify relations between components of a system and to learn to control such system. Through simulations the learner is given the opportunity to practice on his or her own with a variety of situations which resemble "real-life" problems which they might face in the future. And it is this type of practice, which they indicate enhances the learner's problem solving skills.

Brant, Hooper and Sugrue (1991) argued that "(a) simulations establish a cognitive framework or structure to accommodate further learning in a related subject area, and (b) simulations provide an opportunity for reinforcing, integrating and extending previously learned material. Therefore, the effectiveness of a given simulation may depend upon when it is administered within an instructional sequence". Thomas and Hooper (1991) argued that "simulations provide the learner with an environment to focus on without exacting control from the learn, offering unique learning opportunities in all subject areas insofar as simulations permit the attainment of learning goals that are beyond traditional and other computer based instruction methods" (p. 497). According to Andre and Haselhuhn (1995) "simulations provide a potential means of providing students with experiences that facilitate conceptual development." Orlansky and String (1979) compared 30 empirical studies on military students' training achievement when either computer simulation instruction or conventional hands-on instruction was used. Their results showed that simulations not only produced equal or much better achievement gains but required about 30 percent less time than the time required to complete the same course with conventional hands-on instruction.

The inconsistency between the conclusions drawn by various reviewers may be due in part to the poor research design of some studies or the inappropriate use of simulations, as well as poor analysis and interpretation of research data. Salomon (1981), Clark (1983 & 1985) claimed that media research has asked the wrong questions which were based on faulty assumptions, leading to uninterpretable results. The inconsistency could also be due to the different instructional roles expected of simulations in different studies (Jonassen, 1988; Gredler, 1992, Salomon, 1981). Pierfy (1977) noted several design and research flaws in simulation studies. One of these weaknesses was that research studies compared simulations to classroom discussion types of instruction. Such comparison studies are not expected to bring about any meaningful results. And if significant results were found, the differences were often misinterpreted (Clark, 1983, 1985, Salomon, 1981). Sometimes research instruments fail to measure and report what they purport to measure (Dekkers & Donatti, 1981). "Another possible problem is that comparison studies are not very appropriate or sensitive to the students''general characteristics which may interact with instruction to influence learning and achievement" (Gredler, 1992). Gredler further, claimed that simulation researchers frequently forget that simulations function well as a problem-solving tool and, as such, simulation is a tool for enhancing decision-making. Another issue is that researchers have not focused on the key question of the conditions under which simulation is most effective or not effective and what are the tradeoffs between encouraging decision making by the students and giving students information.

The pursuit of computer simulations in an educational context is worthwhile for several reasons. Simulations potentially offer students opportunities to explore physical or biological situations that may be impossible, too expensive, difficult, or time-consuming to accomplish with actual laboratory or real-life experiences (animal dissection or frictionless environments). Even if real-life exploration is feasible, such experimentation can be supplemented by simulations that offer students the opportunity to explore a wider range of variables more rapidly. Such simulated experiences potentially can be used to confront alternative conceptions, produce disequilibration and with appropriate scaffolded instruction, lead students to a new accommodation (Piaget, 1983). In addition to being safe, convenient and controllable, simulations may encourage students to participate actively in learning activities. Despite this potential for the use of simulations, empirical results examining the impact of simulations in science education have been mixed (Akpan 1999). One potential way of resolving differences in existing research is to examine the ways simulations have been used in existing experiments. In almost cases typically, simulations have been used as surrogates for laboratory experiments and, like most, laboratory experiments, have followed didactic instruction on the topic. Nevertheless, some theoretical perspectives suggest simulations may be more effective if used prior to formal instruction. According to Piagetian theory knowledge is constructed through action. Actions leading to impact or disconfirmation of expectation produce disequilibrium and the leaner may construct new mental images to resolve the disequilibrium (Piaget 1954). Bruner (1966) accepted Piagetian theory into the idea that learning requires experiences at an enactive level before iconic and symbolic experiences can become real.

This paper reviews the literature on the uses of simulations in science domains and the conditions under which simulations influence science instruction. Previous research on simulations have found a fair amount of consistency in the results. My goal is to determine the conditions in which simulations seem to positively influence science instruction and the conditions in which they do not influence science instruction. This paper is different from previous reviews of simulations in that it focuses on science instruction. Andre (1986) suggested that creating imagery based representations of experience in episodic memory was necessary in order to provide an experiential base that would allow symbolic representations in semantic memory to have meaning. Paivio's (1986) dual coding theory suggests that creation of imagery based representations along with symbolic representations facilitates understanding. Thomas and Hooper (1991) proposed that simulations could be used instructionally in one of five roles. The first role, experiencing, involving the prior use of simulations to help provide an experiential base that would set the "cognitive or effective stage for future learning" (p. 499). From multiple theoretical perspectives learners need to have non-symbolic experiences within the domain of interest in order to be able to map out symbolic expressions onto perceived reality and to give such symbolic expressions meaning. These multiple theoretical perspectives suggest that providing learners with essential experiences before introducing symbolic descriptions is a part of human learning that has an important educational implication. Therefore, with the use of simulations in instruction, these theoretical perspectives yield a similar educational implication. They all adapted the fact that experiential simulations used prior to didactic symbolic instruction should facilitate students' construction of meaningful understanding of science concepts, principles, and schemata. According to Mayer (1981) simulation provided before instruction may function as a conceptual model that allows students to better understand and encode the didactically presented information than students who experience simulation after didactic instruction.

The rest of this paper is divided into nine sections and a summary. The first section focuses on a brief review of the literature on the use of simulations and dissection in science instruction. The second section investigates the uses of interactive videodisc in animal dissection. Because interactive videodiscs allow students to manipulate variables or to make decisions, they are similar to computer simulations in some aspects. The third section investigates the effectiveness of simulations as an alternative for conventional methods of dissection. The rest of the sections investigate the following subheadings: Significance of dissection in education, controversies over computer simulation for dissection as an alternative to conventional dissection; the use of simulation in science teaching; advantages of computer simulations; educational and a summary of the literature review.

Sources of Data and Inclusive Criteria

This study began by searching three computer databases through Lockheed's DIALOG Online Information Service: ERIC documents, a data base on educational materials from the Educational Resources Information Center, made up of two files, (Research in Education and Current Index to Journals in Education), Comprehensive Dissertation Abstracts, and Psychological Abstracts. Bibliographies cited at the end of each research article provided additional sources. Key words developed for these three data bases yielded over two thousands studies. These were narrowed down by the addition of specific key words to five hundred studies that finally met the three guidelines for inclusion in the study. Since this was too many to review, the addition of the key word 'science' to focus on the science domain further narrowed it down to about two hundred studies. Additional section guidelines used were as follows: The studies had to compare groups that used simulations to groups that did not (for example, simulation versus nonsimulation, video versus nonvideodisc) Second, the studies were performed in actual classrooms in grades 7 and above. Third, the studies reported achievement outcomes for students' performance and cognitive measures for both the simulation and video experimental group and a control group. Excluded from the pools of the studies were those in which the researchers failed to have a comparison group. In addition, papers based purely on the author's opinions, were excluded. Application of these guidelines yielded a set of fifty empirical studies that are reviewed in this paper.

The Nature of Simulations

As indicated earlier, simulation is the use of a powerful tool, the computer, to emulate or replicate an object in a real or imagined world. Alessi and Trollip (1985) categorized simulations into the following four different types:

(1) physical simulations, in which a physical object, such as a frog, is displayed on the computer screen, giving the student an opportunity to dissect it and learn about it, or when a student is learning how to operate a piece of laboratory apparatus which might be used in an experiment;

(2) procedural simulations, in which a simulated machine operates so that the student learns the skills and actions needed to operate it; or when the student follows procedures to determine a solution, as when a student is asked to diagnose a patient's disease and prescribe appropriate treatment;

(3) situational simulations, which normally give the student the chance to explore the effects of different methods to a situation, or to play different roles in it. Usually in situational simulations, the student is always part and parcel of the simulation, taking one of the major assigned roles;

(4) process simulations, which are different from other simulations in that the student neither acts as a participant (as in situational simulations) nor constantly manipulates the simulation (as in physical or procedural simulations) but instead, selects values of various parameters at the onset and then watches the process occur without intervention.

Gredler (1992) categorized simulations into two different types. Experiential simulations, the first category, provide students with a psychological reality in which students play roles within that reality by executing their responsibilities and carry out complex problem-solving in that knowledge domain. Experiential simulations are intended to assist students in situations that are either too expensive or too dangerous to experience in a real world. "Four major types of experiential simulations are data management, diagnostic, crisis management, and social-process simulations" (Gredler, 1992). According to Gredler, experiential simulations are assumed to provide opportunities for students to develop their cognitive strategies because the exercises require that students organize and manage their own thinking and learning. A second type of simulation is a symbolic simulation, which is dynamic in nature and represents the behavior of a system, or phenomena, on a set of interacting processes. The students' role in symbolic simulation is that of principal investigator. Students construct their own learning experiences. Alessi & Trollip (1985); Reigeluth (1987); Bredemeier and Greenblat (1981) argued that when computer simulations are compared to other media such as videotapes or traditional lectures, transfer of learning is greater for the computer simulation group. With transfer of learning, students can apply what was learned from previous instruction to a new situation. But simulations may still be preferred for other reasons, notably cost and safety (Hopkins, 1975). According to Duffy & Jonassen (1992) "simulation is a cognitive tool for accessing information and interpreting and organizing personal knowledge." They claimed that simulation can potentially engage and enhance thinking in learners in science.

Argument about Dissection

There is widespread argument over the question of whether animal dissection in high school biology classrooms is immoral or unethical. On a religious or ethical basis, some argue against the use of animals for dissection. The animal rights activists group, People for the Ethical Treatment of Animals (PETA), have taken the position that present day advances in computer technology, along with new and sophisticated anatomical graphics and models, render the use of animal-dissection labs obsolete. An argument often given by an anti-dissection instructor is that students do not benefit from animal dissection after the first or second experience. A further argument is that the dissection of animals is an unnecessary practice that produces emotional trauma in those participating in the activity. "A major argument against dissections is that it is a desensitizing experience for students," states Barbara Orlans, (1988). This group claims that the experience the students gain in dissection dehumanizes and desensitizes students to the social value of animals. Recently, two researchers (Siemankowski and Macknight 1971) found that successful science majors tend to be at a very high level of visual-spatial cognition. Individuals outside of science-related disciplines were average or at a low level in such aptitude. In another study, Roe (1952) tested 64 eminent scientists of worldwide recognition and found each possessed extremely high levels of spatial conceptualization. Furthermore, biopsychologists have discovered that visual-spatial aptitude develops during the learning years of an individual's life. And such activities as handling, rotating, manipulating, and envisioning objects greatly contribute to the development of visual-spatial perception in the individual. These types of activities are commonly produced in specimen dissection labs Lord (1990). Text, workbook, and computer-based activities rarely stimulate visual-spatial thinking in the student. The 1985 amendments to the Animal Welfare Act (AWA) attempted to improve the treatment of animals in laboratories, to improve enforcement, to encourage consideration of alternative research methods that use fewer or no animals, and to minimize duplication in experiments (Baird and Rosenbaum, 1991). Some states have passed laws upholding the students' rights to refuse to perform dissection. For example, in the states of California, Maryland, Florida, and Pennsylvania, laws have been enacted regulating the use of animals in the biology classroom. In New Jersey, a 17-year-old high school student refused to dissect a cat in biology class. In defense of his stand, the student said, "I think dissection just reinforces the idea that animal life is cheap, I feel it's an inherently objectionable thing to do" (Orlans, 1988, p. 3).

Others, with different moral or ethical views, regard dissection in the classroom as not only legitimate but indispensable to the advancement and improvement of medical knowledge and education. They argue that humans have superior moral status compared to nonhuman animals, and consequently there is no rational or ethical justification to put the same value on animal suffering as on human suffering. For example, Igelsrud (1986) argued in support of traditional animal dissection. He reaffirmed, in the strongest terms, the obligation of institutions to carry on the research programs that have expanded knowledge of disease and led to life saving therapies. Thus, Igelsrud (1986) argued that the use of laboratory animals is totally indispensable. Mackenzie (1988) provided a different argument for simulations. He argued that students who experience science only through the use of computer simulation "may not have the sensitivity to feel compassion toward other life organisms. Real life in the real world is not a computer simulation" (p. 17).

It is important that ways be found to meet the needs of these students who oppose dissection in the classroom and those who may wish to learn about the anatomy and function of organs without sacrificing animals. Science educators, as well as non-science educators, have suggested several alternatives to either substitute or supplement the traditional method of dissection in the science classroom. The alternatives basically provide simulated dissections through the use of various media including interactive videodiscs, videotapes, computer-assisted instruction programs, slides, charts, transparencies, filmstrips and computer simulations.

Comparison Studies of Simulations and Interactive Videodisc (IVD)

Videodiscs are optical discs that store sound, motion pictures, and still pictures. With a videodisc, the information is not read by the computer. The computer functions only as a controller for the videodisc player, accessing and playing the required frames. "Interactive" refers to the user's ability to react to the computer or videodisc player through a command and have the system respond either negatively or positively. This may be as simple as a user striking the wrong key and having a computer correct the user, or a user telling a videodisc player to go in a certain direction in a simulation. Much of the early investigative research on videodiscs focused on whether or not students could learn from them. This section focuses first on studies that compare IVD to various hands-on procedures and then reviews five empirical studies that compare IVD to hands-on dissections.

Ebner, Danaher, Mohoney, Lippert, and Balson (1984) designed a videodisc lesson on the preparation and administration of an intramuscular injection to train student soldiers for service as combat medics and compared it to a conventional lesson taught by demonstration and the hands-on method. Performance testing consisted of actual preparation and administration of an injection, with pairs of trainees injecting each other alternately. Seventy participants were selected and randomly assigned to experimental and control groups (n = 28 and 42). The experimental group was introduced to the task in the traditional way, but they used the videodisc lesson to enhance the demonstration, practical exercise, and study hall phases. At the end of the experiment, both groups were tested twice for proficiency and completed a questionnaire designed to assess their attitudes toward the training. The first proficiency posttest was given immediately after training and the second, which was unannounced, at a later time. The results of the study showed that the videodisc group, compared with the control group, completed the lesson on average 125 minutes more quickly (in two hours instead of four) with no difference in degree of satisfaction and achievement. Thus, the experimental group saved time for their learning experience compared with the control group.

Vitale and Romance (1992) investigate the influence of science knowledge upon attitudes toward science teaching in a one-semester elementary science methods course by embedding a videodisk-based instructional component to remediate knowledge deficiencies. Preservice teachers in the experimental group first learned core concepts in physical and earth science through a series of 24 interactive videodisk lessons and then used the concepts as a foundation for preparing and presenting model science lessons. Results showed that the experimental group overcame their initial knowledge deficiencies by mastering the core concepts presented (means proportion correct on mastery test = 0.91), with multivariate covariance analysis confirming that the experimentals gain in science knowledge was significantly greater than comparable controls in the parallel science methods sections. In addition, the result of mastering the core concepts underlying earth science, preservice teachers using the videodisk instruction also displayed significantly greater confidence in their understanding of science knowledge and more positive attitudes toward science teaching at the elementary levels.

White and her colleagues (White, 1984, 1993; White and Horwitz, 1987, 1993) developed a set of simulations called Thinker Tools. Thinker Tools provided a simulated environment that operated in a manner consistent with the Newton first law. Sixth grades students who experienced Thinker Tools outperformed high school physics students who had just completed a unit on mechanics on a test of conceptual understanding of the first law. White, and Gutwill (1999) showed that leading students through a graduated series of electricity simulations led to the development of dynamic mental models that facilitated understanding of electricity concepts.

Baker (1988) compared the effectiveness of interactive videodiscs and lecture-demonstration instruction in teaching physical therapy students the psychomotor skill of performing a sliding board transfer. A wheelchair with movable armrests and swing-away footrests and a 24-inch long standard sliding board was used to analyze motor performance. The subjects were randomly assigned to a control group (n =15), videodisc group (n =15), or lecture group (n= 15). The videodisc group and the lecture group completed a 10-item multiple choice test on the sliding board transfer before instruction, immediately after instruction, and four weeks after instruction. Learning was assessed with written examinations and performance analyses. The results showed that interactive videodisc instruction was as valuable as lecture-demonstration in teaching this particular psychomotor skill. The results of this study agree with the results of Ebner et al. (1984) which showed that interactive videodisc technology can be a useful educational medium that saves time without loss in achievement and with a high degree of student satisfaction.

Leonard (1985) conducted a series of related studies on learning biological concepts from videodisc versus conventional laboratories. For the study of climate, the traditional hands-on (control) group studied these topics by manipulating graphs, charts, photographs and maps. The experimental group used an interactive videodisc version that contained the same data as that used by the control group but, in addition, contained high-quality video motion sequences of organisms in major biomes of the world. The task for both groups was to infer life types, given climatic condition patterns. For the study of respiration, the experimental group studied the effects of temperature on respiration rate, as measured by the organism's oxygen consumption. Both groups were allowed 3 hours to complete each activity and write a laboratory report, which was subsequently graded. Both groups attended the same lectures and did the same assignments. The videodisc allowed the users to retrieve instant high-quality, "real life" simulated data while they were studying. The videodisc version also allowed students to manipulate the laboratory apparatus on screen. When the hands-on or videodisc activity was completed, each student completed a 3-page questionnaire. The questionnaire assessed the student's satisfaction with, interest in, and appraisal of the educational value of the activity. The two groups did not differ significantly in general interest, understanding of basic laboratory principles, or scores on laboratory examinations. Nevertheless, the interactive videodisc group spent one-half hour less classroom time to complete the task than did the traditional group. Compared with the control group, the students in the video group expressed a high level of satisfaction with the videodisc lesson with respect to the efficiency it afforded.

In a second study, Leonard (1989) investigated the effectiveness of teaching about respiration and climate by using two videodisc systems in two introductory college biology laboratory sections (twenty students each). Students were randomly assigned to either the interactive videodisc experimental group or the traditional laboratory group. As in the previous study, both groups were allowed three hours to complete each laboratory activity and completed a three-page questionnaire that contained items to assess satisfaction with, interest in, and appraisal of the educational value of the activity. No significant differences were found between the two groups with respect to the content learned. Students who used the interactive videodisc gave significantly more positive responses regarding the efficiency of time spent than did the traditional students. They also rated their understanding of the laboratory experiment significantly higher than did the students in the traditional group. The most frequent comments by students in the traditional laboratory groups were that they preferred to set up, handle, and see the actual apparatus and organisms. Some students felt that the "real" lab provided more opportunity to make and learn from typical mistakes.

Leonard recommended that interactive videodisc instruction be considered for use in teaching situations where "(1) higher-quality video resolution is needed for simulations of laboratory or field experiences, (2) tedious or time-consuming observations or experiments are to be performed, (3) complex and/or expensive instrumentation needs to be accessible to a large number of students, and (4) laboratory or field activities are desirable but not practical because of space, time, or travel requirements" (p.101). Leonard stated that his study did not support substituting videodisc/computer technology for "wet" laboratory experiences. As he pointed out, he chose the two lessons in his study because they were particularly suited for videodisc instruction. He mentioned however, that interactive videodisc instruction could "substantially enrich the spectrum of educational experiences usually not possible in a typical classroom setting" (p. 102).

Leonard (1992) compared an interactive videodisc to a conventional laboratory for teaching biology concepts and science process skills. Midwestern college students were randomly assigned to two groups for instruction on respiration and biogeography by means of an interactive videodisc or a traditional laboratory investigation. The five dependent measures in the experiment were (1) grades on student reports, (2) grades on a quiz given within two weeks of each investigation, and (3) grades in a laboratory final exam in which questions were asked about all 13 studies done in the semester. Results showed no statistically significant differences between the two approaches with respect to student grades on laboratory quizzes, laboratory reports, and the final exam. However, the interactive videodisc group required approximately one-half as much classroom time as the conventional laboratory group. The two approaches, therefore, appeared equivalent when the groups were evaluated by traditional learning outcomes, but the interactive videodisc method consumed significantly less time than did the traditional laboratory method. These results were consistent with the results of Leonard's two previous studies.

Looking specifically at studies dealing with computer simulations in science, we find that the picture is no clearer. Shaw and Okey (1985) indicate that when computer simulations and computer simulations plus lab were compared to traditional instruction in middle grade science, the simulation groups showed significant improvement on definition, attributes and values subscales, but not on rule determination. Sperry (1976) also found that there was no significant difference in critical thinking scores between computer simulation treatment and traditional classroom instruction for high school biology students. Hollen (1971) and Jones (1972) found no significant difference in achievement between the computer simulation treatment and the traditional instruction in a high school chemistry course. Traditional instruction may take twice longer as long as CAI, however.

In the area of physics and physical science we also have mixed results. Choi and Gennaro (1985), studying junior high physical science students, and Lang (1975), studying high school physics students, found no significant difference in achievement between the computer simulation group and the traditional instruction group. In contrast to these studies, Boblike (1972) and Lunetta (1972) both found that the computer simulation instruction groups had significantly better achievement scores than the control groups receiving traditional instruction in high school physics. It is not very clear why the research provides conflicting results on the effectiveness of computer simulation, but Okey (1985) speculates that it may be due to a peaking out effect.

Fawver, Branch, Trentham, Robertson, and Beckett (1990) compared interactive videodisc-simulated laboratories with two types of traditional laboratories: a traditional (control) lab consisting of a general cardiovascular physiology participation lab and a traditional fibrillation/positive pressure ventilation demonstration lab. The two laboratory sections (consisting of 85 first-year veterinary medical students) were divided into 12 lab groups with 3 to 4 students from each of the two sections. These 12 groups were randomly assigned to either a traditional live animal laboratory or an interactive videodisc-simulation laboratory to compare the effectiveness and efficiency of these methods of teaching physiology. The IVD laboratory covered the same experimental preparations and the same physiology experiments as the live animal laboratories but also received demonstrations on the use of some drugs not covered in the live-animal laboratory. The videodisc lab presented several versions of most demonstrations to illustrate physiological variations. The students assigned to the live-animal laboratory were expected to review a set of introductory slides before the lab. The students were asked to record the time spent both on reviewing the introductory slides and in the laboratory. The students in the cardiovascular participation laboratory were required to place one venous catheter and one arterial catheter, make recordings from the chambers of the heart, expose and stimulate nerves, and administer vasoactive drugs. A multiple-choice/short answer test was administered to all students after the laboratories. No significant differences were seen between group test scores of the interactive videodisc groups and the live animal laboratory groups, but there were differences in time spent by the two different of groups. The authors concluded that "the interactive videodisc-simulated lab was as effective as the traditional live-animal labs and was more time efficient than the traditional participation lab" (p. 11). The results of this study agree with the results of Leonard's series of investigations, Ebner et al. (1984) and Baker (1988), which show that interactive videodisc technology can be a useful educational medium for saving time compared with other media.

Student acceptance of videodisc-based learning programs has been well documented by some researchers, such as Leonard (1992, 1989, 1985); Strauss Kinzie (1994). Ebner et al. (1984) prepared a teacher-operated interactive videodisc system on intramuscular injection to supplement conventional lecture and laboratory sessions that taught paramedical and basic nursing skills on how to prepare and administer an injection. Students were randomly assigned to either an experimental or a control group in a way that ensured intergroup similarity for independent variables (age, sex, educational level, and military rank). "Both the experimental and the control group attended identical subject matter lectures and watched a linearly-played videotape of the tasks to be undertaken. Each group was then divided into practice sub-groups of 14 students per instructor" (p. 3). The experimental group students were taught with instructor-controlled IVD's, with repeated showings of the nine segments. The traditionally-taught subgroups were given live demonstrations by their instructors. The results showed that the experimental groups not only saved time (three rather than four hours) but also responded more favorably to the teaching experience than did the control groups. The authors asserted that these findings indicate that videodisc-based programs can be effective for training paramedical and basic nursing skills and that their instructors can reduce teaching time with no loss in student achievement and with a high degree of student satisfaction.

Sherwood, Hasselbring, and Marsh (1990) compared chemistry knowledge achievement between ninth-grade students taught with a videodisc lesson called "understanding chemistry and energy." Tenth and eleventh grade students were taught with standard traditional hands on instruction. The hands-on instruction consisted of standard instructional techniques using printed materials (worksheets and quizzes). The dependent measures were achievement in chemistry. Results on both the pretest and the posttest were used to compare the videodisc experimental group with the control group. Because the differences in the pretest and posttest scores were much larger for the experimental group than for the control group, items were analyzed by teachers to determine whether they had been covered during classroom instruction. Students in the experimental group scored significantly higher than the control group on the posttest items that the control group teachers rated as having been covered "a lot" and "some" in normal classroom instruction.

Tylinski (1995) compared a computer simulation with traditional hands-on dissection on junior high students' understanding of the physiological systems of an earthworm. The participants were 110 ninth grade students enrolled in the academic biology classes. The control group consisted of 51 participants (25 females, 26 males) and used hands-on dissection. In the experimental group, 46 students (27 females, 19 males) used the computer simulation. Both the control and experimental groups were to identify the anatomical structures that are a part of the physiological systems of an earthworm and match the structures with their functions. The earthworms were 12 inches long with clitellum. The dependent measures were made up of 40 questions intended to measure students' attitudes and performance. The posttest was administered orally the day after the dissection was completed. No significant differences were found between the control groups and the experimental groups or the genders in either achievement or attitude.

Kinzie, Strauss, and Foss (1993) compared the achievement and attitudes of students who conducted a frog dissection with and without the use of an interactive video-based simulation as a preparatory experience for the actual frog dissection. The participants were 61 high school students enrolled in three general-ability high school biology classes during the 4-day period of the study. The participants in each class were divided into four approximately equal groups. The IVD prep group used the interactive videodisc-based simulation as a preparation for the laboratory dissection, which they then performed. The video prep group viewed a linear videotape containing the same video materials used in the IVD simulation, but without interaction and then performed the dissection. The dissection-only group conducted the dissection without preparation. The IVD-only group used the IVD simulation but did not dissect.

On Day 1 of the study, the students completed the pretest achievement, attitude, and self-efficacy measures. On Day 2, students in the IVD prep group used the simulation; students in the video prep group viewed the videotape; and students in the dissection only and IVD only groups completed library research for a biology assignment unrelated to the dissection. The IVD prep students spent an average of 39.4 minutes on the simulated dissection, and students in the video prep group viewed the videotape for 15 minutes. On Day 3, students in the IVD prep, video prep, and dissection only groups performed the frog dissection. On the fourth and final day, all groups completed the posttest achievement, attitude, and self-efficacy postmeasures.

The IVD prep and video only prep students, who dissected after using a video preparation tool, scored significantly higher on the posttest achievement measures than those who dissected without a video preparation tool. Achievement measures increased significantly from pretest to posttest (pretest, m = 10.05 posttest, m = 21.24). Attitudes toward dissection remained relatively stable from Day 1 (m = 50.89) to Day 4 (m =52.50). Self-efficacy with respect to dissection procedures increased from premeasure (m = 64.95) to postmeasure (m = 72.73). In addition, the results indicated that students in the IVD prep group performed the dissection more effectively than students who received no preparation and more effectively than students whose preparation consisted of viewing a videotape. Those students who dissected after using the video materials as preparation tools learned more about frog anatomy than those who dissected without preparation (Kinzie, Strauss & Foss, p. 995).

Kinzie, Foss and Powers (1993) compared a tutorial computer program to an interactive videodisc simulation; 24 low-achieving college biology students served as subjects. The dependent variable was a test in which students were asked to locate organs on a printed diagram and to name organs shown in videodisc pictures. Observations of the students during learning, interviews, and examination of instructional materials added qualitative data to the study. The "tutorial" computer program allowed the learner to direct or follow the course of study by controlling the content. The videodisc program, called Rana pipiens, consisted of a teacher-generated videodisc on frog dissection. Students performed dissection after viewing the videodisc or tutorial. The results showed significant learning from the pretest to the posttest. There were no significant differences between the videodisc or tutorial groups on organ identification.

Strauss and Kinzie (1994) compared the level of learning and retention of knowledge of the frog's internal anatomy in students using an interactive videodisc simulation with those conducting conventional frog dissection. Two classes (eight and nine students per class) participated. One class consisted of four males and five females, and the other had three males and five females. The students were randomly assigned to either a traditional hands-on method dissection group or a videodisc simulation group. The students in the videodisc simulation group completed the instruction in one class period lasting approximately one hour. The students in the dissection group completed their work in one and one-half class periods. For pretest and posttest achievement measures, students were asked to label 10 major organs on a diagram of a dissected frog, to identify the names of the same organs on a prosected frog, and to answer five multiple-choice questions on dissection procedures. In addition, the students responded to a ten-item attitude test related to how they felt about animal dissection. The pretest was given three weeks before the start of the experiment and the posttest two weeks after the experiment had been completed. The results showed that the two treatment groups did not differ significantly with respect to posttest identification of the frog organs. There were no significant differences in achievement between male and female students on either the pretest or the posttest.

Guy and Frisby (1992) compared interactive videodisc lessons with traditional hands-on instruction with the goal of reducing the number of labor-intensive laboratories in human gross anatomy given to pre-nursing and allied-medical-professions undergraduates at Ohio State University. The subjects were randomly assigned to either a traditional, hands-on cadaver-demonstration lab presented by teaching assistants or an interactive-videodisc computer lab. Both groups covered the same lesson materials. The computer-lab videodisc, composed of a combination of still photos and motion sequences of short demonstrations, depicted everything the students would see in the cadaver demonstration lab. The IVD tutorial provided the kind of student-teacher conversation that usually occurred during the cadaver lab dissection and demonstration practical as well as providing realistic visual material. There were no significant differences between the learning outcomes of students who used interactive-videodisc lessons and those who participated in the traditional, hands-on cadaver-demonstration lab. The researchers suggested that the computer-based-instruction technique could supplement the traditional cadaver-demonstration method of teaching anatomy.

In summary, research on the effectiveness of videodisc technology in science has produced fairly consistent results, especially when various dependent measures of student achievement are taken into consideration. Of thirteen empirical comparisons, one study found that, on traditional paper and pencil on achievement measures, interactive videodisc led to significantly higher achievement than did traditional dissection instruction; twelve studies showed no significant differences in achievement. Thus, IVD and traditional instruction seem to lead to equivalent learning as measured by typical classroom achievement tests. In addition, six comparisons that examined time showed that IVD dissection was faster than actual dissection. Another major finding of these studies was that students usually develop a more positive attitude toward computers in general. In addition, one study done by (Kinzie, 1994) reported that use of a simulated dissection before an actual dissection improved performance on that actual dissection (Kinzie, 1994).

Other Alternatives to Dissection

Because of the political controversy over the use of dissection in education, other alternatives to dissection have been investigated. This section reviews the effectiveness of various dissection alternatives compared to traditional hands-on dissection.

Prentice et, Metcalf, Quinn, Sharp, Jensen, and Holyoke (1977) developed a stereoscopic slide-based auto-instructional program and compared it with standard human gross anatomical dissection as the nucleus of instruction for medical school students. The study developed as a result of problems in the regular curriculum, including the decreased number of hours students spent in gross anatomy instruction and a shortage of anatomical donors for dissection. The program consisted of 70 units, organized by anatomical region. Eight to ten stereoscopic slides (35 mm) were taken sequentially of anatomical dissections after important anatomical structures had been labeled with plastic letters placed directly on the body and after all arteries, veins, nerves, and lymphatic vessels had been painted with acrylic paint to conform with the standard anatomical color code (p. 759). Each unit emphasized a student-centered learning approach, encompassing features as self-pacing, self-testing, self-direction, and reinforcement. Three groups of students were selected: physician's assistant students (PAs), physical therapy students (PTs), and graduate students (GSs). For one-half of the course, the PAs (n = 16) used the slide-based auto-instructional program; the PTs (n = 16) and the GSs (n = 7) used dissection. Students were assessed with student laboratory examinations and written examinations. A pretest was administered before the units were given and a posttest three weeks later. There were significant differences between the groups in terms of ability to identify anatomical structures on stereoscopic slides; the auto slide program students (PAs) performed better than the PTs and GSs. The authors indicated that "the predominant complaint of the students who used the SAA program was the difficulty they experienced in attempting to establish an overall anatomical orientation. This finding is not surprising since there is a limit to the amount of material which can be presented on a slide" (p. 762). They further indicated that the SAA program did not provide the student with time to develop a tactile awareness of the structure of the body, which is important to the understanding of three-dimensional human anatomy.

Bernard (1972) compared first-year medical students who learned anatomy from prosected demonstration cadavers with students who dissected cadavers. The participants were 154 medical school students in their freshman year divided into three groups. Students were ranked in terms of ability and were assigned to conditions to equalize ability between the groups. The experimental group used student-generated prosections. The two control groups did a traditional type of dissection using a standard dissection guide. The experimental group did essentially the same dissections except, that they used a different, specially written, guide. Within each group, eight medical students were assigned to each cadaver. All three groups took the same examinations. The results showed that the experimental group did as well as, and occasionally significantly better than, the control groups. As stated by the researchers, "the prosection demonstration technique saved time, but it is difficult to assess if the time saving was the result of the learning experience" (p. 725). No significant differences were observed in the mean scores of the three groups. This meant that the two groups learned equally from the two methods and one method was not better than the other.

Welser (1969) compared the effectiveness of single concept film loops in a veterinary basic gross anatomy course to the effectiveness of traditional hands-on dissection. The topic was on the innervation of canine limbs. There were three types of instruction: 1) the traditional method consisting of a dissection guide, a prosected cadaver, and student dissection of a cadaver, 2). the dissection guide and student dissection of a fresh cadaver with films loop and 3). the dissection guide, and films loops as the only primary learning aid. Students rotated among the three types of dissection as they proceeded from one of the five units on canine anatomy to the next. The students recorded the amount of time they spent on each unit and filled out an opinion questionnaire as they completed the units. Pre-quizzes were administered before each unit's presentation to assess differences in the quality of groups. Significant differences between groups were found in two of three units. The addition of the loop films was found to benefit retention. A savings of time was also seems to be attributed to the treatment group who had loop films as their guide in a technique-oriented exercise. The group that dissected fresh cadaver with films loop did better than two other groups.

Fowler and Brosius (1968) compared the understanding of 165 skills and attitudes of 165 tenth-grade high school biology students who were taught using two methods. Compared were performing actual dissections of certain selected forms (crayfish, frog, earthworm, perch) and viewing of films of similar dissections. Both groups took a pretest prior to the instruction and a posttest after they had finished the instruction. The tests assessed the following measures: (a) acquisition of factual knowledge, (b) problem solving in biology, (c) understanding the methods and aims of science, (d) attitude toward science and (e) improvement of skill in manipulating certain biology laboratory implements. No significant differences were found in relative effectiveness of all the measures of instruction in improving understanding of the methods and aims of science.

Jones, Olafson and Sutin (1978) studied first-year medical school students who were studying gross anatomy by use of multimedia presentations in place of lectures and use of prosected specimens instead of dissection. No lectures were given, nor was dissection permitted. The multimedia presentations consisted of three basic instructional techniques: 1) slide with presentations audio-tapes, films, and assigned readings, 2) computer demonstrations, and 3) small group discussions around dissected specimens. The experimental group reviewed films or slide-tapes, while the control group watched the teacher's demonstration tutorials. Students met with the instructor around prosected specimens for demonstration tutorials and oral quizzes. The slide-tapes consisted of two-by-two-inch slides of cadaver preparations, models, or graphics with labels and a synchronized narrative on audiocassette. Each slide-tape began with objectives, asked practice questions to reinforce important concepts, and included a pretest and posttest. All instructor prepared examinations contained three parts: practical, written, and reading written instructions. Extramural examinations, the gross anatomy examination of the National Board of Medical Examiners and the Association of Anatomy Chairmen examination were also given. Performance of the experimental groups did not differ significantly from performance of the traditional group on any of the examinations.

Alexander (1970) compared the effectiveness of dissection versus prosection for the teaching of human anatomy to senior physical therapy students at Ithaca College. Students randomly assigned to the control group were required to carry out dissection; students in the experimental group were provided with prepared cadaver specimens. The capacity of students to demonstrate immediate and delayed recall of human anatomy and to apply anatomical information when called upon to solve clinical problems on immediate and delayed examinations were the criteria selected to compare the effectiveness of the two methods. Students were tested on anatomical relationships of muscles, nerves, blood vessels and skeletal landmarks and were required to locate these structures themselves. The results of an analysis of variance indicated that no significant differences in learning could be attributed to the two methods of instruction. Time was saved with prosection compared with the dissection procedure.

The effectiveness of using interactive videodiscs as a teaching or training medium is supported by numerous studies (Hofmeister, 1982; Henderson, 1983; Allard & Thorklidsen, 1981; Bosco, 1986). I an analysis of IVD studies, Bosco (1986) found the most commonly used outcome variables were achievement, user attitude, performance, and learning time. Of these variables, user attitude and decreased learning time affected learning outcomes the most.

Baggott, Lawrence, Shaw, Galey and Devlin (1977) compared the educational effectiveness of slide-tape presentation versus lecture and discussion in medical school biochemistry. The volunteer subjects were first-year medical school students, randomly assigned to three groups; each group was in turn randomly assigned to instruction by lecture only (control), slide-tape only, or a combination of slide-tape and lecture across three biochemistry units. Cognitive achievement was measured by performance on a multiple-choice examination. No significant differences were found among the lecture slide-tape, and combination groups. Comparison of total learning times revealed that the slide-tape group spent 28 percent less time and the combination group 22 percent less time learning the material than did the lecture group.

McCollum (1988) compared students' knowledge gained by dissection with that gained through a traditional lecture presentation. The 300 students (179 white, 171 nonwhite; 200 female and 150 male) involved in this study were enrolled in biology in five secondary schools of a large metropolitan school district. The students were taught by seven teachers whose experience in teaching biology averaged seventeen years. The classes completed a pretest and were randomly assigned to either the experimental or the control group. The experimental group performed the traditional frog dissection to learn about frog structure, function, and adaptation. The control group received lecture only to learn about the same components of the frog and then completed multiple choice questions. A posttest was administered after the treatment. Analysis of covariance (ANCOVA) was employed to determine if differences in posttest achievement scores of the dissection and lecture groups were statistically significant. The results of suggested that the lecture method led to higher scores compared to the dissection method.

In summary, the results of other alternatives to dissection empirical research studies indicated that other alternatives to dissection can be as effective as hands-on dissection in promoting student learning of anatomy and morphology of organs. Of eight empirical comparisons, three studies found that, on traditional paper and pencil on achievement measures, alternatives such as film slide and still photos demonstrations led to significantly higher achievement than did traditional dissection instruction; five studies showed no significant differences in achievement. Thus, other alternatives and traditional instruction seem to lead to equivalent learning as measured by typical classroom achievement tests. In addition, four comparison studies that examined time, showed that other alternatives were faster than traditional dissection. Overall these results support the contention that, when learning is measured by typical achievement measures, other alternatives to dissection can be as effective and efficient as traditional hands-on experience.

The achievement measures usually consisted of paper and pencil tests on anatomical body parts and functions. It does not seem completely surprising to see that in the case of simulation of dissection alternatives simulation seem to work at least as well as non-simulation for dissection in teaching recognition of anatomy and morphology presented via diagram as tested in paper and pencil tests. None of the particular advantages of dissections, such as the three dimensional nature of the organs, and how they fit together in the body are assessed in such tests. On the other hand, such tests represented the traditional assessments used in assessing knowledge of anatomy in science classes. As such, these paper and pencils tests are representative of real criteria used to evaluate student progress.

The available research clearly suggests that simulation alternatives can lead to equivalent performance to non-simulation instruction on such tests. While it is not clear exactly how effective computer simulations can be or what areas of cognitive development are most effectively stimulated, it is clear that they are at least as effective as traditional laboratory-lecture methods while requiring considerably less time. Marks (1982) and Spain (1983) both contend, that even greater achievement can be obtained with computer simulation if the learners program the simulation themselves.

Computer Simulations

. Science describes simulation as "the process of designing a model of a real system and conducting experiments with this model for the purpose either of understanding the behavior of the system or evaluating various strategies for the operation of the system. Simulations may prove to be a valuable medium through which educators can tap the power of the computer to help learners develop higher level cognitive processes and problem solving skills. Ellis (1984), Marks (1982), Nakleh (1983), and Switzer and White (1984). A number of authors have argued that, in science courses, classroom simulations potentially have an important and valid role in creating virtual experiments and problem-based microworlds that allow students to use instruments and monitor experiments, test new models, and improve their intuitive understanding of complex phenomena. They indicate that simulations can help students to identify relations between components of a system to learn about the system and to control them. Through simulations the learner is given the opportunity to practice with a variety of situations which resemble "real-life" problems which they might face in the future. Simulations encourage the skill of synthesis by applying what the student already knows to a unique situation and thus, strives for a higher level of cognitive functioning by providing the student with a variety of responses. Simulations can also provide students with learning environments in which students search for meaning, appreciate uncertainty, and acquire responsibility.

The use of simulations in science education can make significant contributions by providing appropriate learning opportunities to diverse learners and motivating students to learn science, both inside and outside of the school environment Educational simulations present students with problems and allow students to utilize the simulation as a powerful tool to carry out investigations and to solve problems. Educational simulations are designed both to teach content and to enhance higher-order problem-solving skills. Simulations allow learners to explore and manipulate variables and then obtain results from the various manipulations. Those results should provide feedback to their thinking and learning processes in science.

There are, of course, well established arguments that differences in learning between computer and non-computer instruction may be attributed to uncontrolled effects of different instructional methods, content, or novelty (Clark, 1985). This section emphasizes research that compares the results of instruction with and without computer simulations. The organizing question of this section is: under what conditions does the use of instructional technologies such as simulations provide more efficient and effective learning than the learning obtainable without the use of such instructional technology, such as traditional methods of teaching and discussion? My stipulation is that when students program the simulation, thereby actively gaining and demonstrating a firm grasp of the concepts being learned. While simulations can be an effective educational tool, there are not very many good science simulations available (Shaw, Okey and Waugh, 1984). Several educators feel that the solution to this dilemna is for teachers and students to program their own simulations for better understanding of the concepts. Dewdney (1984) and Lehman (1983) discuss the essential elements in the development of a predator-prey simulation such as Sharks and Fish or simpler interactions. Hord (1984) describes the steps in the development of any effective simulation materials, while Spain (1983) and Thomas (1983) discuss the general plan for development of science simulations. Marks (1982) and Shaw, Okey and Waugh (1984) emphasize the necessity for providing good documentation for the implementation of the simulation in the classroom Wells and Berger (1985/86). The organization of this section is based on subject matter and is limited to the science domain.

Choi and Gennaro (1987) developed a computer simulation model that paralleled traditional hands-on laboratory experiences in the teaching of the concept of volume displacement. They compared learning between junior high school students who used hands-on experiences and those who used the simulation and assessed students' understanding of volume displacement. Students, 63 males, 65 females, aged 13 and 14 years, were selected from five eighth-grade earth science classes. The dependent variables were achievement scores obtained from a posttest and a retention test. The independent variables were treatment, sex, and time of day. Students were randomly assigned to either the experimental group or the hands-on group (control group). The experimental group (31 males, 32 females) was taught by means of a computer-simulated experiment in graphics and animation to help students visualize the concepts they were learning. The traditional, hands-on group (32 males, 33 females) was taught the same concept, volume displacement, but used hands-on laboratory experiences designed by the researchers. Both groups completed five experiments on volume displacement. The control students required two full class periods to complete the learning experience experiment. The experimental group required 25 minutes to complete the simulation. Both groups were asked to determine: (1) the relationship between the volume of an object and the volume of water it displaces, (2) the relationship between the shape of the object and volume of water it displaces, (3) the relationship between the mass of an object and the volume of water it displaces, (4) the relationship between the size of an object and the volume of water it displaces, (5) the relationship between type of liquid and the volume of displacement by an object. No significant differences were found between the computer simulated experimental group and the hands-on laboratory experimental group on either the immediate or the delayed posttests.

In two separate but related studies involving samples of elementary education preservice teachers and eighth-grade students, Baird, Koballa and Thomas (1986) and Baird and Koballa (1988) studied the learning of the science process skill of hypothesis testing. Students who received only computer-presented textual instruction on hypothesis testing were compared with students who used a computer simulation program game that provided practice in testing hypotheses. The dependent measures, which were administered as a pretest and a posttest, consisted of 22 items taken from the Group Assessment of Logical Thinking (GALT) test developed by Roadrangka, Yeany and Padilla (1983), as well as self reports of satisfaction with the computer simulation or text activities. In both studies, students who completed the simulations did better on the logical thinking items than did students who only completed the text. Also, in both studies, students who used simulations reported higher satisfaction with the instructional materials than did students who used the computer-presented text version.

Mills, Amend, and Sebert (1985) developed a water resource management simulation (WRMS) to serve as a water education training tool for elementary, secondary science, and other secondary teachers. They compared 56 students who used this simulation to 95 nontreatment control students with regard to knowledge and attitude toward water management. The multi-user interactive computer simulation (MICS) was designed to improve the understanding of the major factors in wise water resource management. In this study, the simulation, a model display of hydrologic information, provided opportunity to cooperatively develop and evaluate water management strategies. The results of this study showed that knowledge scores of the teachers who used WRMS were significantly higher than scores of teachers in the nontreatment control group, who did not use WRMS. This result was true for elementary, secondary science and other secondary teaching majors. No significant difference in attitudes were found between the scores of WRMS users and non-users.

Hollen, Bunderson and Dunham (1971) compared computer simulation with traditional laboratory exercises in qualitative chemical analysis in introductory college chemistry. In this qualitative analysis computer simulation, stimuli were in the form of telex-typed output; supplemental colored slides were displayed where needed for the students. Students keyed in their answers to questions and the computer responded by displaying the correct answers. If the students were wrong, the computer provided feedback by correcting the answers as well as indicating the next step for the students to perform. In the traditional sections of the qualitative analysis scheme, students were given an outline of the analysis that followed the outline of a standard text. Schematic analyses were group separations, the silver group, the copper-arsenic group, the aluminum-iron group, the combined alkali metal and alkaline earth groups, and the anion. The dependent measures were performance and achievement and the amount of time it took for the students to complete the task. Pretests and posttests were given to each student. No significant differences were noted between the two groups with respect to performance and achievement. But the experimental group completed the task in less time than did the students in the traditional control group.

In three experiments in a high school chemistry class, Bourque and Carlson (1987) compared the effectiveness of traditional hands-on laboratory exercises and simulations. The effectiveness was assessed in two ways, by testing knowledge of the chemical concepts implicit in the laboratory exercises and by measuring students' attitudes towards the computer-simulation and the hands-on laboratories. Across the three experiments, three computer simulations developed by J. E. Gelder were compared to parallel hands-on laboratories: (1) acid-base titration, (2) equilibrium constant of a weak acid and (3) Avogadro's number. The simulations were presented on the Apple IIe microcomputers. In both the laboratories and simulation exercises, each student prepared a lab notebook, which was to include a statement of purpose, the general procedure, and the construction of a table for collecting data for each activity. In addition, students responded to a list of questions in the affective domain intended to gather information from their personal learning interaction with the computer simulation or with the laboratory format. A 10 item quiz was given as a posttest to evaluate comprehension of the concept involved. The results indicated that, on this posttest, the traditional hands-on laboratory exercise produced significantly higher learning scores in both experiment 1, the acid-base titration and in experiment 2, the ionization constant. No significant difference in performance was observed for experiment 3, the determination of Avogadro's number.

Fortner and Schar (1986) compared effectiveness of computer simulations to effectiveness of non-simulations with respect to computer awareness and perception of environmental relationships by college students. Undergraduates (n =110) enrolled in an "Introduction to Conservation of Natural Resources" course participated in this study. The experimental treatment group used workbooks and three simulations that were incorporated into the course as individual learning modules; the control group worked with comparable workbook modules, textbooks, and reference materials that covered the same topics as the computer-simulated modules. "Each simulation module consisted of (a) written background information about the topic, (b) instructions for operating the computer program, and (c) a summary worksheet." Content and presentation techniques were assessed on the basis of knowledge the students gained on subtest instruments and an environmental relationship perception survey. Simulation programs utilized a method of demonstrating in a simplified version of real-world conditions, providing learning experiences, and allowing students to manipulate variables that offered them feedback. A computer awareness survey that measured attitudes toward computer enjoyment, anxiety, and user efficiency was also administered. The results showed that, on the knowledge subtest, the experimental group performed significantly higher than the control group on knowledge and application assessment.

Fennessey (1972) compared the effectiveness of simulation exercises, simulation games, and conventional instruction in elementary and junior high school ecology classes. The subjects were 1,874 students in 60 third, fourth, and eighth grade classes in parochial schools. In this study, the experimental unit was the class and not the students. Classes were randomly assigned to treatment groups. The control group teachers were given a resource booklet containing all the information and materials for Man in His Environment, but all references to the simulation exercises were deleted. The teachers in the simulation exercises group received a resource booklet and a copy of Man in His Environment, referred to as "the Ecology Kit." The teachers in the simulation game group received the resource booklet, the Ecology Kit, and a set of rules for converting "Make Your Own World" into a simulation game. The teachers in all three groups were told to use the materials provided as the basis for a teaching unit of ten 45-minute class periods, to be taught during a specified two-week period. Teachers in the simulation exercises and simulation game groups were also asked to use each simulation exercise at least once and to use the exercises as much as they could. The teachers in the simulation game group were asked to use only the modified version of "Make Your Own World." The effectiveness of the three experimental treatments was measured by means of an objective test and attitude questionnaire, given on the tenth (final) day of the unit. No significant differences were found between the mean scores across the groups, which indicated that the three treatments were all equally effective.

Munro, Fehling and Towne (1985) studied the effects of student control of feedback messages during interactive dynamic simulations providing skill training in perceptual, motor, and decision-making skills such as piloting vehicles or performing the job of an air traffic controller. Group one, the intrusive feedback group, received an error message. The less-intrusive feedback group received an error message only if the student requested it. These students were assigned to one of the two experimental groups in alternating order as they arrived for the experiment. All students first viewed a six-minute videotape explanation and demonstration of the Air Intercept Controller task. This interactive dynamic simulation consisted of a series of text presentations that were described in the videotaped introduction. It also presented simulation segments that the student was asked to interact with by use of a control keyboard. Number of errors per problem was used as one measure of learning. The mean number of errors was 9.17 for the students in the less-intrusive group and 15.67 for the students in the intrusive treatment group. This difference, which was highly significant, suggested that students in the less-intrusive group learned more than those in the intrusive group and the techniques used for the less-intrusive group had promoted more learning in dynamic skill training.

Rivers and Vockell (1987) compared computer simulations to traditional lecture in teaching middle and lower-middle-class high school biology students to solve problems. The experimental treatment group used a simulation program on Apple computers called "BALANCE: A Predator-Prey Simulation". This simulation allowed students to explore the interrelated variables affecting predator-prey relationships. In groups of three to five, the experimental students prepared for simulations by using laboratory guides, determined what variables to use in the simulation, and planned and conducted experiments using the simulations on the computers. Each computer simulation was integrated with a teacher's guide and a student laboratory guide, which provided additional laboratory and real-life experiences. The control group was taught the equivalent topics in a noncomputerized fashion using textbooks, lectures and traditional laboratories. The same amount of time was spent on each topic in both the control and the experimental treatment classes. The students were to analyze the data collected and draw their conclusions in small groups. The students were given a pretest and posttest for each simulation. The individual unit posttests measured specific problem solving skills directly related to each unit. The groups did not differ significantly in the rate of gain. (However, the experimental simulation students gained more than students in the control group). Rivers and Vockell concluded that "the impact of computer simulations varies, apparently depending on the content of the simulations and the nature of the thinking processes being measured" (p. 22).

Spraggins and Rowsey (1986) compared the effect of simulation games and worksheets on learning in 83 high school biology students (42 males, 41 females) of varying ability. In this study, worksheets consisted of one or two pages that included questions to be answered, tables to be completed, or space for students to make sketches, diagrams, or maps. The experimental group played simulation games that introduced the current lesson and also completed assigned worksheets related to a topic previously covered in class. The control group played simulation games pertaining to a past lesson and were assigned worksheets that introduced the current lesson. Lessons were the same for both groups. The investigator taught all of the classes. The experimental simulation games used were geologic time charts, the cell game, and a game on blood flow. The control simulation games used were Predator: The food chain game, environmental rummy, and an endangered species game. A mean split the Science Research Progress Test scores were used to classify students into control high and low ability groups for comparisons. An achievement test was developed by the investigators to measure the level of mastery of concepts being taught with simulation games and worksheets. A retention instrument developed by the investigators was used to assess the retention of information by the experimental and control groups. The dependent variables of achievement scores on Geologic Time Table Measure, Cell Biology Measure, and Circulatory System Measure, were analyzed within a factorial design with treatment, ability, and sex as the independent variables. Achievement gains of students who were taught by the simulation game method were the same as achievement gains of the students who were taught by using worksheets. Likewise, there were no significant differences in retention scores between students taught by worksheets and students taught by simulation methods of instruction. Low-ability females who used simulations games scored higher on retention than low-ability female who used worksheets. In contrast, low-ability males who used worksheets scored higher on retention than low ability males who used simulation games. Spraggins and Rowsey commented that they observed a spirit of cooperation among the low-ability females participants of the gaming groups. Because the low-ability girls tended to discuss the situation before responding to the questions, this discussion reflected on their positive learning outcomes. In contrast, the low-ability males were more independent and competitive, therefore, there was less discussion and cooperation among the group members.

Based on the results of computer simulation empirical research studies reviewed in this section, it appears that computer simulation can be as effective and as efficient a medium for delivery of instruction as non-simulation experience. Often empirical research studies, four studies found that, on traditional paper and pencil on achievement measures, simulations led to higher achievement than non-simulation instruction; six studies showed no significant differences in achievement. Thus, simulation instruction seems to lead to, at least, equivalent learning as measured by typical classroom achievement tests. Although some students may not have liked the simulation, the simulation did at least produce similar achievement results to non-simulation experience. In addition, one study that examined time showed that the simulation was faster than the non-simulation instruction. These results support the contention that when learning is measured by typical achievement measures, simulation instruction can be as effective as non-simulation instruction. While the methodology of any one of the present studies might be questioned, the failure to find any significant advantage for hands-on experience in any of the studies surely cannot be interpreted as support for hands-on experience over simulation instructions.

Simulations and Conceptual Change Model

Research on how students learn science indicates that they tend to use their misconceptions about science concepts to comprehend new concepts. The use of computer simulations can assist students in changing their naive misconceptions about science and thereby help improve student learning. This section reviews the use of simulations in helping students overcome misconceptions.

Mayer, (1981) argued that a simulation provided before instruction may function as a conceptual model that allows students to better understand and encode the didactically presented information. Students receiving such a model may be better able to recall the presented didactic information and to reason with the principles taught in transfer situations. Thus, students who receive simulation after didactic instruction may find it difficult to make sense from the model with which to assimilate the instructional information. That being the case, during didactic instruction, they may not be able to encode a given information into cognitive structure as well as students who had ha prior simulations.

Carlson and Andre (1992) compared simulation to traditional conceptual change text instruction to overcome student preconceptions about electric circuits. The participants (36 males, 47 females) were enrolled in introductory psychology courses and received extra credit points for participating. Two methods were used in this investigation. In the first method, students used traditional text (TT) which combined portions of two commercially available middle school/high school texts that covered basic electrical concepts. The conceptual change text (CCT) consisted of the TT plus sections which challenged students' preconceptions by presenting diagrams of possible circuits and asked students to predict, in writing, what would happen in the circuit and then presented evidence that countered typical preconceptions. There were two sections of the test; the first dealt with basic electricity and the second with the calculation of current and voltage. The simulation portion was a HyperCard stack which made it possible to design and test circuits. The simulation consisted of a short tutorial on using the mouse and the circuit simulation and simulation itself. Students were presented with the problems in building a circuit. The total posttest contained 66 multiple choice items; 26 of those items asked conceptual questions about series circuits. Students who studied using CCT scored significantly higher than those studying using TT. More importantly, the simulation group also had a higher conceptual model score than the no simulation groups.

Chambers, Haselhuhn, Andre, Mayberry, Wellington, Krafka, Volmer and Berger (1994) compared a simulation experience to hands-on experimentation on acquisition of a scientific understanding of electricity. This study compared reading of three versions of a text to reading combined with simulation or hands-on experience. In the first method, students were directed to use a Macintosh computer simulation in which they constructed simple electrical circuits in order to test their beliefs and predictions. In the hands-on approach, students use kits to physically build the electrical circuits to test their ideas about electricity. The students in this study were in introductory psychology classes and received extra credit for their participation. The data were collected in college classrooms and computer laboratories. There were five conditions of the text: 1) traditional text only; 2) augmented traditional text, consisting of the traditional text with an additional explanatory text, examples, and diagrams; 3) conceptual change text which consisted of the traditional text and conceptual change features that activated and refuted typical misconceptions; 4) conceptual change text with simulation which used the same text, but asked students to test their predictions about circuits by using computer simulation; and 5) conceptual change test with hands on experience, which used the same text, but asked students to test their predictions by building circuits. Students were expected to write their predictions and observe what happened when they tested those predictions. Prior to the experiment, both groups completed a pretest with a diagram of a flashlight cutaway, and students were asked to explain how it worked. The students also completed a 4-item pretest consisting of slides of circuits and were asked to explain if the circuits would work. The students received an immediate and a delayed posttest that assessed conceptual understanding of electrical circuits. The posttest administered to the students consisted of circuits and noncircuits; and students were to show which circuits would or would not work and why?

Significant differences were found between groups with regard to acquisition of scientific knowledge about electricity. However, a comparison between genders within a condition showed that males scored significantly better than females in the traditional text and augmented traditional text groups. This result suggests that males had more experience and perhaps more interest in electricity than females had. But the performance of males remained the same regardless of whether they had read the conceptual change text, traditional text or augmented traditional text. The researchers reported that the females found the simulation easier and somewhat superior to the hands-on experience and speculated that the lower experience of females with building electrical circuits led to frustration with the hands-on method.

Andre and Haselhuhn (1995) compared students who completed either a Newtonian motion or a non-Newtonian computer simulation either before or after didactic instruction. Participants were students in an introductory psychology classes. The participants received extra credit for their participation. The independent variables were the type of computer activity (simulation or game) and the position of the computer activity (before or after reading the text). The two types of computer activities were: 1) a simulation designed to illustrate Newtonian principles of motion and 2) commercial games with a non-Newtonian motion. The motion simulation allowed the student to explore the effects of applying impulse forces to a body at rest or moving in a particular direction of space. The computer games were given to students either before or after they read a text dealing with Newtonian motion. The control group was to read the text and then complete the posttest. Students were required to complete a 45-item questionnaire that asked questions regarding their sex, class year, academic major and age. In addition, they completed a vocabulary test and 6 questions concerning their interest and experience in physics. A 4-item multiple-choice motion knowledge pretest was completed by all the students. A 45-item multiple-choice posttest that assessed student understanding of the concepts of rectilinear and curvilinear motion and transfer of the learning of Newtonian principles was also completed by the participants.

There was a significant difference in the posttest means found among the control, simulation-before and simulation-after text conditions. It was also found that male students who engaged in a computer simulation lesson before reading the physics text performed better on a test of transfer knowledge than male students who completed computer games before reading text. This result was consistent with those obtained by Brant, Hooper, and Sugrue (1991) who found that genetics simulation before lecture enhanced learning more than the same simulation after lecture. The results suggested that the use of computer simulations before didactic instruction in physics may be more effective for males than for females students.

Hargrave and Andre (1993) examined the use of computer simulations, reflective journals, and peer group interactions to facilitate conceptual change about electricity. The participants were 116 undergraduate students (92 females 24 males) enrolled in media course for preservice teachers elementary education. The students were randomly assigned to four treatment groups: 1) the computer-based didactic lesson control group (CP) completed a computer-based instructional lesson concerning simple electrical circuits that used traditional instructional design, 2) the conceptual change computer simulation group (CCCS) who completed a computer-based instructional lesson concerning simple electrical circuits and used a conceptual change approach, 3) the conceptual change computer simulation and reflective writing group (CCCSW) who completed the same lesson as the CCCS treatment group and also recorded their perceptions toward computer lesson in student journal, and 4) the conceptual change computer simulation, writing and peer group interaction group (CCCSWPGI) who completed the same lessons as the CCCSW treatment group and in addition, took part in small group discussions about electrical concepts in the program. Students in the control group completed a didactic HyperCard lesson similar to that found in a typical textbook whereas the experimental group completed a simulation lesson about electrical circuits. The simulation lesson encouraged students to become cognizant about how electrical circuits worked. The students used the computer to built electrical circuits and then test whether the circuit worked. A 29 multiple-choice item posttest, adapted from Carlson & Andre (1989) and Chambers and Andre (1991), which measured students understanding of basic electrical circuits, was administered to the students. Five posttest subscores were calculated from this posttest. In addition, 4 calculation items tested students' ability to recall and apply Ohm's law to calculate voltage, resistance, and amperage. The posttest was administered twice to the students on different occasions. The results indicated that the CP treatment group scored significantly than the CCCSWPGI treatment group on the BULB subtest score, but that the simulation groups did significantly better than the control group on the SINK subtest score.

Zietman and Hewson (1986) investigated the effects of instruction by using computer simulation to diagnose and remediate alternative conceptions. The microcomputer simulation was used to evaluate the effectiveness of the conceptual change model of learning through the use of a computer simulation facilitating a change in the student's perceptions as cited in Tylinski (1994). The microcomputer presented two capabilities: 1) a simulation experiment that identified the different conceptions that students hold and 2) a practice test diagnosing the students conceptions in respect to the anatomical functions and identity of the particular organs among other organs in the system. Their results indicated that:

(1) Simulation is effective and can be credibly represent reality, and

(2) remediation produced significant conceptual change, particularly in those students holding alternative conceptions.

Students hold a variety of alternative conceptions about natural phenomena that may actively interfere with the development of scientific conceptualizations. In the search for ways to influence the conceptual development of learners, computer simulation has emerged as a possible vehicle for helping students learn and for effecting conceptual change (Zietman & Hewson, 1986). In this section eight empirical research articles were reviewed based on the use of computer simulation to effect conceptual change. On achievement measures, four found that the use of simulations can effect conceptual change and can lead to higher achievement; three found no significant differences in achievement. In one comparison that examined gender, the results indicated that using simulation before didactic instruction was more effective for males than females. Overall these results support the contention that computer simulations can be helpful in significantly altering students' misconceptions.

The Controversy Over Computer Simulation and Dissection

Opponents of simulations claimed that simulations in science education are too abstract, minimize human involvement, cannot promote the learning of biological concepts, or teach interrelationships of the anatomical components of the animal (Mackenzie 1988, p. 7). On the other hand, there are some who endorsed the use of computer simulations to replace the traditional hands-on method of dissection because simulations can allow the dissection to remain "real" while eliminating political controversy, dissection errors and expensive laboratory apparatus (Orlans, 1988; Murphy, 1986; Winders and Yates, 1990). This section review the arguments made for and against the use of dissections and alternatives to dissection in biology classrooms.

Perhaps the most positive statements that can be made about computer simulations of dissections are that some studies show that use of computer-simulations improves students' learning, reduces students' learning time, and usually fosters development of a more positive attitude toward computers, compared with the traditional instructional approach (Flower & Brosius, 1968; Alexander, 1970; Bernard, 1972; Baggott, 1977; Jones, Olafson & Sutin, 1978; Strauss & Kinzie, 1994). A number of authors have suggested that computer-simulations represent a real-life model in which the student plays a role and interacts with the computer. Simulations have been used in most high schools and elementary schools throughout the nation to model scientific processes in the classroom. The recent unique advances in the teaching of science have been in the use of computer-simulations. One application of simulation techniques has been as a replacement for the large numbers of animals used for dissection in research.

While an overview of the literature indicates that significant numbers of science and non-science educators express whole-hearted support for using simulations in science education laboratories, there are those who oppose such usage and label it "counterfeit science." One of the leaders, and perhaps the most eloquent, of the opponents of computer simulations as replacements for hands-on laboratory dissections, Schrock (1984) claimed that computer simulations inserted into the school curricula would not help students in any way to develop positive values from reality, but might function as additional step in isolating students from real-world experience. Schrock went on to say that "Computers do have an important and valid role in instrumenting and monitoring experiments, testing new models and improving our intuitive reach, analyzing real data, and simulating labs that are impossible, impractical, or too dangerous to run. But their use beyond this poses a threat in value education, the so-called 'affective domain' in educationese" (Schrock, 1984, p. 254). Schrock added that the sales pitch claiming "installation of computer lab simulations will save large amounts of money consumed by chemicals and lab supplies... money that can go for other curricula needs, etc." misses the point (p. 4).

Bross (1986) argued that most conclusions drawn from computer-simulations "cannot be scientific" because they are "the imitation of nature with programming and graphics and do not follow directly from natural laws" (p. 13). He believes that the skills acquired through the use of computer simulation activities are perhaps beneficial to students, but if they displace the intended science curriculum, then a serious and negative value shifts occurs. Students may develop computer literacy along with science illiteracy. Similarly, Schrock (1984) added that "we have sufficient experience indicating that computer-simulations inserted into the current curricula will not help students develop values from reality, but will be an additional step in isolating students from real value-producing experiences" (Schrock 1984, p. 254). "The majority of science teachers are aware that verbal descriptions, theoretically simulated diagrams on the screen, and even audiovisual reproductions are no substitute for the real thing and carry no weight compared with hands-on laboratory demonstrations that are live, captivating, and real" Bross, (1986 p. 28). Wood (1979) suggested that the use of simulations should be limited to biological experiments which, by reason of difficulty of technique, danger to life, or lack of time, would be unavailable to students. Danger to life refers not only to the investigator, but also to the use of simulations to help reduce the number of experimental animals sacrificed in teaching.

Murphy (1986) claimed that most computer advocates believe that computer simulations should function as a supplement, rather than to replace, laboratory or experiences that students gain from fieldwork. Murphy went on to suggest that living organisms should be included in the science curriculum as a part of teaching and learning science. On the other hand, Murphy questioned whether computer simulation instruction was as effective as dissection as a supplementary tool to the instruction. Murphy claimed that any student who experienced dissection only through computer simulation would not only lack experiential skills to handle required laboratory tools, but may not exhibit the compassion toward lower life forms. He suggested that educators should be as explicit as possible and be aware of the nature and limitations of computer simulations. And if computers are to be used in science education, it is imperative educators understand the differences between the terms used like 'model' and 'modeling' and to use them carefully. If not, there is a real danger of serious confusion in the minds of biology students. In the study of physical phenomena, MacKenzie (1988) stated "that the microcomputer simulation can allow the experiment to remain 'real' while eliminating the tedium and errors in gathering and analyzing data and displaying results" (p. 23).

In MacKenzie's opinion, although simulations are capable of imitating or replicating what is 'real' especially in the science laboratory, does not means that simulations can act as a total replacement to traditional hands-on dissection. He went on to question whether students should really be learning that science is full of amusement, easy, precise and fun as simulation seem to make science appear? In MacKenzie's view computer simulations may be useful in some situations because simulations can be close enough to real laboratory apparatus and instruments that sometimes may be too expensive and hard to find or use, or may require frequent arduous calculations. These useful features do not make simulations compatible to hands-on dissection in his view, however. In support of MacKinzie opinion, I believe that no patient would like to be operated on by a physician who had studied exclusively from computer simulations of human structures, anatomical functions, and locations or had used simulations confirm certain diagnostic tests and conclusions. Winders and Yates (1990) logically compared the traditional science laboratory method to computerized science laboratory simulation without specifically defining these methods. They claimed that traditional hands-on science laboratories provide certain essential skills necessary for the development of a scientifically literate society that are frequently missing from computer simulations. Hands-on labs, therefore, should not be totally replaced with computer simulations and models (p.11-12).

Winders and Yates supported Mackenzie (1988) by saying that "computer simulations suffer by their abstract presentation of real-world phenomena. Students may develop a false sense of reality or security in the simulation of situations which are complex or potentially dangerous, just as with video games" (p. 5). MacKenzie had concluded that the computer simulation-based laboratory was at one extreme (abstract and minimizing human involvement), and the traditional experiment at the other (inaccurate, of limited scope, and labor-intensive). Winders and Yates concluded, "real life in the real world is not a computer simulation! And the use of computer simulations in science education is not a panacea to scientific illiteracy."

Murphy (1986) also warned investigators against the default values of the simulation and basing simulations on mathematical models. He recommended that they use analogues of nature instead, while being "as explicit as possible about the nature and limitations of the simulations" (Murphy, 1986 p. 20). I agree that any student who experienced science only through computer simulations would lack the necessary skills required to properly handle expensive equipment or may lack feelings and human compassion for the fellow humans. Recent evidence makes it clear that there is correlation to the rise in violent acts or other influences on social and cognitive processes from computers and video simulations. The average child now witnesses more than 8,000 murders and about 1000,000 other violent acts by the time she or he completed elementary school. Estimates are that by age 18 a youngster will have seen 40,000 murders and another 2000,000 acts of violence on video simulations. Reviews of research have found that repeated exposure to violence on computer simulation promotes a tendency to engage in aggressive behavior, such as getting into fights, disrupting the play of others, escapist, fantasies and sexual behaviors (Postman, 1979).

As was noted in the introduction and in opposition to these opponents of dissection, many educators and theorists have argued the advantages of simulations (e.g., Alessi and Trollip, 1985; Brant et al., 1991; Duffy and Jonassen, 1992; Bredemeier & Greenblat, 1981; Gredler, 1992; Igelsrud, 1986; Orlans, 1888, Reigeluth, 1987; Thomas and Hooper, 1991). Research from military and other settings suggests that interactive simulations can be an efficient and effective tool for training psychomotor tasks (e.g., Olsen & Bass, 1982; Saettler, 1968). Thousands of military personnel have been trained to rapidly and effectively perform tasks critical to their own survival and to military effectiveness through the use of simulations (Olsen & Bass, 1982). If this is the case, interactive computer simulation may prove to be especially useful in science education and interactive dissection simulations may prove to be an effective vehicle for teaching even the psychomotor skills involved in dissection. It seems clear that the use of simulated frog specimens affords beginning students a firsthand look at a vertebrate that has many body structures in positions and arrangements similar to that of the human. Simulated dissection goes beyond the visual investigation of textbook drawings and photographs and allows students to examine quite real appearing structures and to utilize quite real dissection procedures. Moreover, the applications of simulations to science teaching are nearly unlimited. In visually rich subjects such as life science, simulations can provide a compact library of experiences that could replace bulky and expensive slide collections. Such visual databases in part represent one potentially valuable use of simulation technology. Such inexpensive simulation databases potentially represent a flexible resource that a science teacher might use in many different ways to promote effective learning.

Thus, in spite of these different opinions on whether or how simulations should be used, in my opinion, the use of simulations in education can be successful in translating imagined situations into something that is very productive and a real learning experience for students. Simulation is neither good nor bad. It depends on its use and the purpose for its use. For example, as supplement to dissection, the use of simulation before dissection may provide experiential based skills in removing specific hidden parts of the anatomical structure which may be difficult to view or remove in the traditional dissection classroom. In my view, computer simulation is an important cognitive tool that can increase students' ability to investigate and understand science. The following section will discuss reasons that justify the use of simulations in the teaching of science.

Use of Simulations in Science Teaching

The increasing availability of computer technologies in schools (Becker, 1991) has made it possible for more thorough investigation of their influence on students' learning, achievement, and attitude change. In biological science or physical chemistry, for example, experiments at times can be very expensive, too difficult, or too dangerous for the students to conduct. Through simulations such experiments can be conducted and the intended results actually observed. Simulations make flights through space, man visiting the moon and more complex impossible tasks become possible. In years to come, creatively designed simulations, may make even more impossible events such as humans traveling almost at the same speed of light possible to experience. The unique capacity and ability of simulations to present phenomena in multiple perspectives and to allow the learners to interact with the dynamic imagined worlds, creates a means of making learners the master of their own learning processes.

Computer simulations as instructional medium has gained more popularity and enthusiasm in the past few decades.. In science education classroom simulations provide an opportunity to apply the scientific method to the solution of problems by providing learners with a rich and variable learning environment in which they can master skills and content, develop understanding of concepts, inquire, explore various cause-and effect relationships, develop strategic thinking, and quickly test multiple hypotheses (Well and Berger, 1985/86). Similarly, as suggested by (Coburn, et al 1983) simulation offer a bridge between concrete and abstract reasoning (Berger, 1984), simulations allow students to postulate abstract concepts in a more concrete manner (Ellis, 1984), convey insight into complicated phenomena and relationships (Goles, 1982), engage student interest and allow them to practice lab techniques prior to the actual laboratory experience (Nakhleh, 1983), provide the learner with an active role in the learning process (Queen, 1984), help students observe and understand dynamic processes (Switzer and White, 1984), and enhance decision making skills (Zamora, 1984). According to (Shaw, Okey and Waugh, 1984), simulations provide a realistic cause-and-effect environment in which students can quickly, safely, and efficiently investigate to learn. Goodman (1982) reminds the advocates of simulations that they must prove that students using them lean something.

In my view, the primary purpose of computer simulation in biology or life sciences is to provide students with experience before actual dissection activities and to allow fundamental experimentation that would not be otherwise possible. There is some evidence from Kinzie et al. (1993) that simulations can enable students to improve actual dissection. Additionally, evidence as provided by Strauss and Kinzie (1994) suggests that simulation can allow students to observe animals' physiological systems and interrelationships more easily. In some simulations, students can make changes in a dynamic system to learn about the functions of the system. The rest of this section further addresses advantages of computer simulations.

Computer simulation is one resource available for pre-service teachers who are teachers trainees to learn how to integrate technology into their classroom teaching (Becker, 1983). However, teacher training may represent the largest single barrier to computer use in the science classroom. There is growing evidence that computer simulations can help provide an environment for practice of science process skills (Becker, 1983). If it is true that computer simulations in growing numbers are available to science teachers, in what ways can these new tools be most effectively used to teach specific science process skills? Because of simulations' potential, students can understand abstract concepts in a more concrete manner and interact with phenomena normally not accessible in a traditional classroom. Computer simulations can display some distinctive advantages when used as an alternative to the traditional method of dissection. The first is cost-effectiveness and cost-efficiency. Some potential problems exist in medical schools over the lack of cadavers in the laboratory because too few people donate their bodies to science. This problem can make dissection very expensive and, even if money is available, the supply of cadavers may be inadequate. Although most of the alternatives are expensive and require an initial outlay of some money, over time, the money is saved because the purchase of computer simulations is a one-time event, and they can be used repeatedly over long periods of time compared to the cost of purchasing preserved frogs or cadaver specimens every few months. Simulated specimen alternatives may have a longer longevity, according to (Akpan, 1989; Hepner 1993; Strauss & Kinzie 1994, 1991; Fawver et al. 1990) and are non-disposable items in contrast to traditional animal or cadaver specimens. Another advantage is repetitiveness. Students can repeat the given dissection assignment without the restriction of time limits, until they feel they have learned something (Hepner, 1993). Moreover, most of the alternatives that are available are self-directed or self-paced, making them more suitable for students with various disabilities. Most alternatives enhance motivation because students are active participants in the learning situation, as compared to their role in traditional classrooms.

Another important advantage of simulations is that they promote a transfer of learning (Alessi & Trollip, 1985). Transfer of learning consists of skills or knowledge learned in one situation being applied in other situations. In my view, simulations potentially can promote good transfer of learning because what is learned in the simulation in one situation or class can usually be transferred to the real-life situation. Use of computer simulations before actual dissection of a frog in order to study internal structures, muscles, and locations as well as functions of organs can result in better transfer of knowledge than dissection after simulation (Strauss and Kinzie, 1994). In addition to saving time, simulations may motivate students. Students may be filled with a high-spirit of excitement when they encounter, for the first time, a sea star or earthworm to dissect via computer simulation. Efficiency in decision-making, by providing a base of previous meaningful experiences, is another way in which a simulation can enhance learning (Gredler, 1992). Simulations provide the learner with an environment that is conducive to learning compared to a regular classroom without simulations (e.g., Alessi and Trollip 1985; Strauss and Kinzie, 1994; Kinzie, Strauss, and Foss 1993; Kinzie, Foss and Powers, 1993; Rivers & Vockell, 1987; Leonard, 1992, 1985, 1989; & Choi & Gennaro, 1987; Guy & Frisby, 1992).

Value of Simulations and Instructional Strategies in Science Education

Research studies have indicated that the use of computer simulations of dissection, compared to the traditional hands-on method of dissection, provide comparable results in improving student attitudes and achievement, reduce instructional time (e.g., Kinzie, Strauss, & Foss 1993; Kinzie, Foss & Powers, 1993; Guy & Frisby 1992; Fawver, Branch, Trentham, Robertson, & Beckett 1990; Leonard 1992, 1989, and 1985; Choi & Gennaro, 1987). Simulations can reduce instructional cost, and provide high-quality, timely, feedback responses to the user. Simulations entice users to manipulate variables and observe their effects in an environment that may be completely impossible, impractical, or ineffaceable compared to other methods of instruction ( Rivers & Vockell, 1987). One most unique and powerful aspect of simulations use in science education is interactivity. The key here is that the student must do something. From educational research we come to know that learning involving "doing" is retained longer than learning via listening, reading, or seeing. Simulations in science education provide education which is non-linear and is not teacher-directed. This type of learning offers an inquiry approach in science education. The learner is actively involved in exploring and discovering. In science education simulations can turn over a great deal of power from the lecturer to the learner. Instead of the teacher directly leading students through specific content, the teacher provides an environment in which students can discover and explore. One useful strategy in science education is getting students involved in the best way to motivate them to learn. Simulations seem to hold a natural attraction for students to learn science.

Summary

This paper has reviewed some major issues on empirical research related to the use of simulations in science education. Among the issues examined were theoretical, logical, and speculative claims made about the advantages of simulations in science education. Many authors have argued that simulations should improve science learning by making learning more realistic and active and by permitting students to experience situations in simulation that are impossible, impractical, too dangerous, or too expensive to experience in reality. Other authors argue against simulation because they believe simulation reduces the reality of the learning experience in science education.

The research reviewed in this paper suggested that simulations can lead to equivalent learning to hands-on dissection or other hands-on alternatives experiences when learning is measured by paper and pencil tests (Kinzie, Strauss, & Foss 1993; Kinzie, Foss & Powers, 1993; Guy & Frisby, 1992; Fawver, Branch, Trentham, Robertson, & Baeckett, 1990; Leonard, 1992, 1985, 1989; Choi & Gennaro, 1987). Further, the research suggested that simulations used before other educational experiences can facilitate learning more than simulations used after other experiences (Andre, et al. 1998; Brandt et al. 1991). One particularly important finding in this review was the Kinzie et al. (1993) study. While several studies noted above have reported positive benefits for the use of simulations prior to didactic instruction, the Kinzie et al. study suggested that a prior interactive videodisc dissection simulation could enhance subsequent actual dissection performance. The present review suggested that simulations can be educationally sound and useful; it also made clear that additional research is needed to more fully understand the educational impact of simulations in science education. One direction for future research is to explore the sequence in which simulations are used relative to other instruction. A second issue to be explored is how individual, group, and cultural differences interact with simulations. Do simulations work equally effectively for the different genders, for students with different personality, metacognitve or cognitive style characteristics, for students from minority groups, or for students from different cultures? Does the use of simulations have to be adapted to such differences in order to be effective? Another issue is the long term use of simulations. Most of the studies reviewed here have involved short term use of simulations. Will simulations have the same educational effects when they are integrated into semester or year long course sequences and are a typical part of the student's day? These questions can only be answered by additional research.

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