Research: Science & Education edited by
Chemical Education Research
Diane M. Bunce The Catholic University of America Washington, D.C. 20064
Spatial Perception Skills of Chemistry Students Sharon L. Coleman and Albert J. Gotch* Chemistry Department, Southeast Missouri State University, Cape Girardeau, MO 63701 Historically, some studies have indicated a correlation between cognitive development and achievement in the sciences (1–11), whereas others have suggested that factors such as background knowledge (10, 12, 13), attitude (8, 14), curricular emphasis (15), or verbal ability (14) are main determinants. However, in terms of cognitive development, researchers have pointed to spatial ability as playing a fundamental role in the formation of skills and understanding of concepts in mathematics, chemistry, and earth sciences (1, 2, 11, 16–19). One would be tempted a priori to assume a significant correlation between spatial perception and achievement in chemistry because the visualization and mental manipulation of molecules in three-dimensional space are important for understanding many chemical concepts (4–6). For instance, the spatial orientation of orbitals, molecular geometries, crystal structures, R and S configurations of organic molecules, structure–function relationships, and group theory applications all require visualization and mental manipulation in two or three dimensions. In addition to interest in the development of spatial ability in students, several investigations show a statistically significant gender difference in spatial perceptual abilities, with males performing better than females (18– 22). A major investigation showed differences between the genders at all levels from grades 5 through 12 in biology, chemistry, and physics (21). Another revealed that the gender gap is closing in mathematics, but not in science (20). In contrast, two studies of non-Western populations indicated a gender difference with women performing better than men (23, 24), but additional cultural factors may be involved in these populations. Assuming the importance of spatial ability to success in chemistry and other sciences, it is unclear whether training or other interventions might improve general performance and specifically, women’s performance. One inquiry indicates that gender differences may remain unaffected by intervention (25). The more generalized approach of meta-analysis shows that the difference between genders in science achievement depends in part on the subject matter being tested (26). Spatial ability as a separate factor in intelligence was first proposed in the 1920s by Spearman (7). Later studies led to a large number of measures of spatial ability, which were organized by Michael et al. (27) in the 1950s into two main components: spatial visualization and spatial orientation. Definitions of these terms vary depending on the researcher and the specific study. We provide the following definitions, consistent with usage by previous workers (14, 27, 28). Spatial visualization is recognizing the relationships of a representation with respect to its parts and an external frame of reference. Thus, spatial visualization involves recognizing, retaining, and recalling configurations in which movement of the figure or parts of the figure occurs. Spatial *Current address: Chemistry Department, Benedictine College, Atchison, KS 66002.
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orientation is the ability to remain unconfused by changing orientations in which visual stimuli are presented. Thus spatial orientation involves imagining simple and rigid transformations of whole objects.1 Linn and Peterson (29) characterize these categories as spatial perception and mental rotation, respectively. Methods Two proven testing methodologies of spatial ability have been developed. One method requires concrete manipulations of blocks; the other is via paper-and-pencil tests. Both areas of spatial ability have been tested using these methods (1, 2, 6, 16, 30). In a study of chemistry students, Bodner (1) found that men performed significantly better than women on questions dealing with concepts of crystal structure. For spatial assessment, Bodner’s method relied heavily on concrete manipulations—the rotation of threedimensional blocks. Our study, however, employed only a pencil-and-paper test. The instrument used in our study is “An Inventory of Piaget’s Developmental Tasks” (IPDT), a 72-item multiplechoice test. Its validity and reliability were demonstrated by Milakofsky and Patterson (30), who outlined several subtests and identified an associated area of cognitive development for each. We based our spatial investigation on a subset of twelve questions using the stated cognitive development areas to evaluate spatial ability. We also investigated the difference between genders for two other questions that we believe discriminate the analytical abilities of our students. These questions (numbers 36 and 60) were noted by Milakofsky and Patterson as two of the most difficult test items on the IPDT. Number 36 addresses liquid displacement, requiring the student to recognize that this is a result of volume, not mass or density; number 60 requires an understanding of the relationship between the area of a rectangle and its perimeter. Three introductory chemistry courses, PH-218, CH-181, and CH-185, were initially included in the study. PH-218 enrolls nonscience (education) majors with little or no high school chemistry. CH-181 is an introductory chemistry course for nursing and allied health majors, who generally have had one year of high school chemistry. CH-185 is our general chemistry course, which is taken primarily by majors in chemistry, biology, premed, and pre-engineering. Almost all these students have had one year of high school chemistry and many have had two years. Thus we would rank these classes—in terms of the science background of the students, from least to most prepared—as PH-218, CH-18l, and CH185. In the 1980s PH-218 was not offered; the comparable course was CH-100. The tests were administered in the first half of each semester before topics of molecular geometry and hybridization were introduced. Two sections of CH-185 were exceptions to this. The Fall 1992 section had completed this material in lecture and performed a lab based on
Journal of Chemical Education • Vol. 75 No. 2 February 1998 • JChemEd.chem.wisc.edu
Research: Science & Education measuring bond lengths and bond angles using ball-andstick models. The Fall 1994 section was the same as Fall 1992 except that it also included a recitation lecture using computer models—both stick-frame and space-filling models of VSEPR structures of H2O, NH3, CH4, and CCl4 (the same molecules used in the ball-and-stick laboratory experiment). Our study began as a test of the cognitive development of students enrolled in freshman chemistry courses from fall 1979 to spring 1982. In readministering the cognitive development test to students from 1992 to 1994, we expanded our study to include analysis of two additional variables, spatial ability and gender. Lastly, using a subset of our test population, we studied how the use of concrete and computer models might affect cognitive performance in the spatial area. Analyses were performed via t-tests, z-tests, chisquare, and analysis of variance (ANOVA) techniques. Results of the Study
nation of women’s scores from the 1980s to the 1990s showed no significant difference in either the overall scores or spatial subset scores. A breakdown of overall IPDT test scores above 62 by gender is shown in Table 3. The decrease in percentage of students scoring above 62 in the 1980s and those scoring above 62 in the 1990s is statistically significant. In addition, analysis of several discriminating questions confirms the deterioration of scores from the 1980s to the 1990s These discriminating questions (#36 and #60) were noted to be the most difficult by Milakofsky and Patterson (30) and are those for which a relatively low percentage of students correctly answered that particular question, regardless of gender. We found question #49 to be the discriminating question of the spatial subset (this question involves shadow projections in 3 dimensional representations). Thus results for questions #36, 49, and 60 are presented. For all three discriminating questions there was a drop in percentage of students answering correctly between the 1980s and the 1990s. However, only the results for overall score and question #36 are statistically significant. Further inquiry reveals a statistically significant gender difference in overall performance and on two of the three discriminating questions (#36 and #49). This is seen in two ways. First, despite a 6% decrease in women scoring >62% on the IPDT between the 1980s and 1990s the difference is not statistically significant. This is also true of the women for all three discriminating questions. In contrast, 59.1% of the men scored >62% in the 1980s, compared to only 45.6% in the 1990s, and this decrease is statistically significant. Inspection of Table 3 also shows that a significant gender gap existed in the 1980s and persisted into the 1990s. To discern the effects of the use of models on a student’s spatial performance, an analysis of the CH-185, 1990s subset was done with respect to the spatially discriminating question #49. As noted above, the Spring 1993 section was given the IPDT before working with the models lab, Fall 1992 was given the IPDT after working with the models lab, and Fall 1994 was given the IPDT after working with the models lab and being exposed to computer models. Since question #49 was the discriminating question in the spatial subset, the results for this question are expected to be a sensitive measure of the effects of intervention. Table 4 shows the results of the analysis of question #49 by course section and by gender. Surprisingly, there were no statistical differences between classes, by section, based on comparison of the numbers of students answering question #49 correctly and incorrectly. Also, on a section-by-section basis, there were no statistical differences between men in the 1990s subset; nor were there statistical differences between women on a section-by-section basis. On the other hand, the gender difference persisted in two of the three sections (Spring 1993 and Fall 1994) and in the overall percentage answering question #49 correctly in the 1990s subset.
Milakofsky and Patterson found that 62 was the average score on the IPDT test for their college students. Therefore we determined the average scores and percentage of students scoring above 62 for each course (Table 1). Data were taken from both the 1980s and 1990s databases. They show that scores for CH-185 were higher than for the other two courses, although no significant difference was found in the 1990s data. The variation in the background of students in the three courses is apparent in the percentage of students scoring above 62 on the IPDT test. We use these data as an indicator of formal thought development and possibly math/chemistry preparation. The sample size of the major study was n = 755, taken over several semesters in CH-185 from the early 1980s and the early 1990s. We excluded scores from the two introductory courses (PH-218 and CH-181) because they enrolled a higher percentage of women than men, which might bias the data in a gender-based study. The following reported results focus on three important areas: (i) gender differences with respect to general cognitive development and specifically with respect to spatial ability, (ii) observed changes in cognitive development and spatial ability over time, and (iii) intervention methods to enhance spatial ability. Table 2 summarizes overall scores and spatial subtest scores by gender for CH-185 students. The gender differences seen in the overall means indicate that in the 1980s, men had higher scores than women. The 1990s data show a continuing but decreasing difference between mean scores: in the 1980s, men outscored women, on average, by 2.7 points, whereas in the 1990s this difference was 1.9. In ANOVA analysis of data for the spatial subset of 12 questions, the 1980s men out-scored women by x¯ = 10.9 to x¯ = 10.2; this yields an F ratio of 23.594 (p < .0005). The 1990s data again show a gender difference in the subset. Although a smaller difference than in the 1980s data, this is also statistically significant (F = 6.662, p < .010). Table 2 also shows some results of the longitudinal study. First note that there is a significant difference between the mean score of the 1980s students and the 1990s Table 1. Student Performance on IPDT during Two Time Periods students in the overall IPDT test 1990s Data 1980s Data scores. In addition, overall and Class Score Score > 62 Score Score > 62 spatial achievements by gender n n { ( x ± SD) (% of students) ( x{ ± SD) (% of students) from the 1980s and 1990s were compared. Although overall PH-218/CH-100 a 82 57.9 ± 7.8 31.7 118 54.4 14.0 means on IPDT scores for men CH-181 31 57.1 ± 8.5 35.5 177 58.3 40.0 dropped significantly, there was C H 1 8 5 3 9 1 5 9 . 5 ± 8 . 6 4 8 . 6 3 6 4 6 1 . 6 ± 6 . 4 59.9 no analogous drop in the spatial a PH-218 was instituted in the 1990s. The comparable class during the 1980s was CH-100. subset for men. However, examiJChemEd.chem.wisc.edu • Vol. 75 No. 2 February 1998 • Journal of Chemical Education
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Research: Science & Education der differences that appear in our investigation substantiate earlier studies showing Overall 72-Item IPDT 12-Item Spatial Subset of IPDT Group that a gap in cognitive development and/ n Subgroup p Mean Score F -Ratio p Mean Score t -Value or spatial abilities exists between males and females. We also conclude that the gap All Students has decreased over time. However, it is de1980s 364 61.60 10.64 creasing not because women’s scores are 3.69
