Sex and Cognitive Differences: Are They Real?

Throughout the ages, the differences between men and women have been debated by scientists, comedians, and everyone in between. Sayings such as “Men are from Mars, women are from Venus” attempt to describe how different males and females are from each other. Beyond human curiosity, the differences are important in policy issues. A woman who ran over and killed her boyfriend with a car was conditionally discharged from jail after her defender argued that she was suffering from “premenstrual derangement” at the time (1). Clearly, sex differences in behavior affect more than cultural curiosities, leading to different treatments by the law. It is therefore important to study such differences to avoid unfair differential treatment.

Much research has been performed on the dichotomy between the brains of men and women. One widely accepted biological difference is that men have better visual-spatial ability, such as mental rotation of complex 3-D structures, while women are more capable at verbal processing tasks such as remembering words. A number of studies back this claim (2, 3, 4).

These differences may be due to hemisphere specialization. Males tend to have a specialized right hemisphere for spatial processing, meaning that for a visual task a male individual uses the right hemisphere more than the left. Since visual-spatial processing tends to be lateralized to the right hemisphere, it then makes sense that males would have higher scores in tasks like mentally rotating a 3-D object. One study showed that men have more gray matter in the left hemisphere, while women have a more even distribution (5). This correlates with greater right-hemisphere specialization in males which many believe explains why males seem to have better visual-spatial processing.

In early childhood, males and females both have right-hemisphere specialization for visual tasks (6). Around age four, there are no sex-related differences in specialization or performance in visual tasks. Male specialization of the right hemisphere for spatial processing starts around age six, when differences in task ability start to show up; in contrast, females develop more even usage of the hemispheres for visual processing (7). After puberty, males tend to outperform women in visual tasks, measured by accuracy and rapidity, though the difference decreases with age, possibly because everyone’s reaction time slows with age (2).

One influential and famous experimental method for testing cognitive differences between males and females is the rod-and-frame test. Developed by psychologist Herman Witkin, the rod-and-frame test places subjects in a pitch-dark room, sitting in a chair facing a large lit frame. A lighted rod bisects the frame. In one version, as the experimenter tilts the frame, the subject must adjust the rod to be parallel to the walls, ignoring the tilt of the frame. In another version of the study, the experiment tilts the subject’s chair in addition to tilting the frame (1). This test is often quoted as proof that men perform better in visual-spatial processing tests.

Eleanor Maccoby and Carol Nagy Jacklin analyzed the results of twelve studies that used the rod and frame test mostly from the 1970s. They found that in five of the studies, or 42 percent, no sex-related differences were found (8). The other seven studies found that males performed better on the test, but there could be unaccounted factors that may have created a male bias.

Anne Fausto-Sterling theorizes that there are possible factors that could create sex bias in the rod-frame test. One possible unaccounted factor is that, in the rod-frame experiments, female subjects are placed in a dark room with a male experimenter; this may create feelings of vulnerability for the female subject. Another factor is the shyness of a subject. In one study, subjects had to ask the experimenter to adjust the rod little by little. A shyer person might not be as nitpicky in asking for adjustments, leading to less accurate scores that do not reflect the subject’s actual ability (8).

The study design is therefore very significant in obtaining data that reflect any real variations in cognitive ability. Differences in early development may mean women and men have divergent neuronal physiology. However, having physiological differences doesn’t necessarily mean that performance at a task should be worse, only that there may be different strategies used to perform the same task. When a test design overemphasizes one strategy, it could create seeming variability in ability. It is critical to keep in mind that personal biases can intentionally or unintentionally enter the research methodology, especially with research that is personal to the scientist since it concerns the differences that he or she may have from the other sex. A researcher might unconsciously and unintentionally design a task that favors a certain sex, skewing the results.

Biology has touched both extremes of the gender behavioral difference field. The 1970s feminist movement argued that all cognitive differences were from environmental factors that pressured girls to be demure and nurturing, ignoring math and other “manly pursuits,” while others said that all variation was inherent, suggesting that women were naturally not inclined to perform as well as men in jobs like engineering that require frequent spatial thinking. As further research is designed and performed, we can keep in mind that the actuality of male-female dichotomy is probably somewhere in between the two poles of gender difference research. For now, we could say that men are, in general, actually better at visualization and females at verbalization, while realizing that the observed differences are usually marginal with a large overlap in ability.

REFERENCES

1. A. Fausto-Sterling, Myths of Gender: Biological Theories about Women and Men (New York: Basic Books, 1985), p. 5.
2. P. Jansen, M. Heil, Exp. Aging. Res. 36, 94-104 (2010).
3. T. Kozaki, A. Yasukouchi, Int. J. Neurosci. 119, 59-67 (2009).
4. T. Koscik et al., Brain Cogn. 69, 451-9 (2009).
5. R. C. Gur et al., J. Neurosci. 19, 4065-4072 (1999).
6. C. Etaugh, R. B. Levy, Percept. Mot. Skills. 53, 621-2 (1981).
7. D. F. Witelson, Science 193, 425-27 (1976).
8. E. Maccoby, C. Nagy Jacklin, The Psychology of Sex Differences (Stanford, CA: Stanford University Press, 1974), tables 3.7 and 3.8, as replicated in Fausto-Sterling, p. 29, (Table 2.3).