Running head : STIMULUS PRESENTATION AND SEX ROLE Effects of Stimulus Presentation and Sex Role on Sex Differences in Mental Rotation

Two factors influencing sex differences in mental rotation, stimulus presentation and sex role, were investigated. Effects of stimulus presentation were explored by comparing scores on the Vandenberg Mental Rotation Test (a pictorial, paper-based test) to scores on an identical test composed of three-dimensional models of the Vandenberg figures (an object-based test). There were significant main effects of sex (male score > female score) and of test type (object score > pictorial score), but no significant interaction. Thus, the data did not support the hypothesis that the reduced demand on working memory, provided by the object test, would reduce the differences between female and male performance. An effect of practice was observed, as the tests were administered withinsubjects, yielding increased scores on the object-based test if the pictorial test was taken first. A relationship between degree of masculinity and test score showed support for the hypothesized association between sex role and mental rotation ability. Effects of stimulus presentation and 3 Effects of Stimulus Complexity and Sex Role on Sex Differences in Mental Rotation The origin of sex differences in cognitive abilities is a persistent and widely studied mystery of cognitive science. Although many investigations have been made, little has been determined about why the differences occur. One central issue concerns the differing performance of males and females on tests of spatial ability (specifically on tests of mental rotation) as these tests almost invariably exhibit superior performance on the part of males (Delgado & Prieto, 1996; Casey, 1996; Mann, Sasanuma, Sakuma, & Masaki, 1990; McGee, 1979; McWilliams, Hamilton, & Muncer, 1997; Sharps, Price, & Williams, 1994; Vandenberg & Kuse, 1978; Voyer, 1995). Given that men in many cultures tend to dominate technical fields in which spatial ability is a key factor, further research into whether cognitive abilities are sex-determined seems warranted. McGee (1979) has reviewed a series of studies that suggest importance of spatial abilities for technical work such as engineering, science, drafting, and design. Relevance is also illustrated in the relationship observed between mental rotation ability, math self-confidence, and scores on the math portion of the SAT among females (Casey, Pezaris, Nuttall, and Benbow, 1995). Since the SAT is a critical test determining college admissions and thereby the future of an individual’s education, it seems pertinent to study how to improve female mental rotation performance so that performance on the SAT might also be improved. Needless to say, the difference in spatial ability among men and women seems to have a very practical consequence. Conflicting theories exist as to how and why the performance discrepancy in spatial ability arises. One view attributes the disparity to biological factors such as Effects of stimulus presentation and 4 neural, hormonal, and genetic differences between males and females. According to one such model, (Geschwind & Galaburda, 1987, cited in Mann et al., 1990) brain structure differences are caused by the hormone testosterone and its tendency to slow the development of the left hemisphere. The negative effect on the left hemisphere causes a compensatory enlargement of analogous structures in the right hemisphere, the area of the brain that is primarily involved in the reasoning required for visuospatial tasks. Since testosterone, on average, tends to be more widely present in males, it seems reasonable that the male superiority exhibited in spatial tasks such as mental rotation is a result of a more highly developed right hemisphere (Mann et al., 1990). Some corroborating evidence for this model is exhibited by Mann et al. (1990), who showed that sex differences with similar patterns existed for both Japanese and American high school students. The students were given a battery of cognitive tests composed of both spatial and verbal tasks, including the Vandenberg Mental Rotations Test. Since such similar results were observed independent of culture, this suggests that biology may play an important role in determining cognitive performance. Alternative theories have focused on “performance factors,” or external circumstances about the test or testing environment that may inadvertently bias the final score (Voyer, 1995; Delgado & Prieto, 1996; Sharps et al., 1994). According to this view, differences in socialization experienced by men and women may ultimately lead to different attitudes about the testing situation and affect performance (such as reluctance/willingness to guess, timed conditions, instructions for the test, or even the sex of the experimenter). The goal is to show that the sex difference can be eliminated when the test is administered in a properly “unbiased” environment. Effects of stimulus presentation and 5 Evidence from studies that have investigated the effects of performance factors is somewhat contradictory. Voyer (1995) did not observe sex differences in untimed conditions with the Vandenberg MRT, while a difference was present under timed conditions. Differences in effect size were also found across four different scoring procedures: the male advantage increased as the scoring methods more strictly controlled for guessing. Although the scores computed by each method were not significantly different, researchers concluded from the trend that guessing behavior does play a role in the male/female score discrepancy. Delgado and Prieto (1996), however, found that males outperformed females both in timed and untimed conditions in a similarly designed experiment, and concluded that guessing behavior was similar for both males and females. Discrepancies among these conclusions may be an effect of differing definitions as to what constitutes guessing, as well as the instruments used to measure spatial aptitude (the former researchers used the Vandenberg MRT, the latter a combination of the DAT-SR and Rotation of Solid Figures Test). Whatever the case, it is clear that an agreement has yet to be reached as to whether performance factors of spatial tests actually play a significant role in the score differences between males and females. Few studies have incorporated both biological and environmental factors into their theoretical framework. Casey (1996) provides an exception, as her study investigated the variability of spatial ability within females. This study proposed the relatively unexplored view that biological and sociocultural factors interact to produce the sex difference in performance. The study identified a group of females believed to have a genetically determined brain organization advantageous for spatial ability, Effects of stimulus presentation and 6 selected through familial handedness patterns (for further discussion on genetic influences, see Casey, 1996). Out of these women, Casey hypothesized that only those having sufficient experience with spatial thinking (assessed by choice of college major) would perform at the level of males. Results supported this hypothesis, in that the selected group of females outperformed all other groups of females (even those who had “spatial” college majors but not the ideal brain organization, and vice versa). The targeted group did not show significant differences from males. These observations led Casey to conclude that the female spatial competence is not dependent on brain structure or experiences alone, but by the interaction of both. The ideas discussed above represent only some of those proposed to explain sex differences in spatial abilities. Because the ultimate cause is likely to result from a combination of many factors, it is the goal of this study to focus on two specific aspects that may contribute to the larger puzzle. The present study analyzes the role of two domains, cognitive processing ability and gender-specific stereotypes, on male/female performance in mental rotation. In the cognitive domain, two processes have been identified as components of mental rotation activity. McGee (1979) defines these as spatial visualization (the ability to mentally manipulate, twist or flip objects), and spatial orientation (the ability to maintain a consistent, “unconfused” reference to the object being manipulated). LoringMeier and Halpern (1999) distinguish two analogous components defined as transformation (manipulation of an object) and maintenance (storing a representation of the object). Loring-Meier and Halpern also identify the importance of working memory for these two components, finding that males were significantly faster in performing both Effects of stimulus presentation and 7 maintenance and transformation tasks. This suggests that females are not as proficient as males in tasks requiring heavy demands on visuospatial working memory. Other studies suggest that females have more difficulty as a task’s level of abstractness increases so that more visualization is required. McWilliams, Hamilton, & Muncer (1997) compared male/female performance on a pencil-and-paper mental rotations task (where the three-dimensional images to be rotated are depicted as drawings), with the same test constructed from three-dimensional models. Participants answered with a simple decision of whether two figures (adapted from Shepard and Metzler, 1971) were the same or different. A standard sex difference was found on the paper-and-pencil version, but there was no significant difference in male/female performance on the version consisting of three-dimensional models. This indicates that females have more difficulty when the object to be rotated must be visualized from a more abstract depiction. It has also been observed that similar rotation experiments using figures that are more easily visualized have failed to produce significant sex differences. Sharps et al. (1994) studied the effects of object type on male/female test scores using a manipulation of the Vande