Sexual dimorphism has been, and continues to be, a major point of discussion within Psychology. Research has established that sex differences in some spatial tasks exist. However, the extent to the sex differences has been over-exaggerated by laypersons, the media and some researchers. Furthermore, a universal understanding of why sex-related differences occur has not been agreed upon; some argue biological, some social, whilst others argue an interactionist approach. Therefore, this essay aims to describe what evidence there is for sex differences in spatial ability and evaluate the extent to which studies and their findings can be relied upon as findings of sex differences can have huge implications, such as the impact on gender stereotypes and career choice.
There are definitional problems when determining what constitutes ‘spatial ability.’ Some argue it is unitary; Lane and Dratt (1979) defined a single spatial visualization factor, whereas others argue that it’s made up of multiple components; Linn and Peterson (1985) defined three categories of spatial ability consisting of spatial visualization, spatial perception and mental rotation. However, some tests that fell into the spatial visualization category, such as the Identical Blocks Test (Stafford, 1961), also had mental rotation elements (Voyer, 1995). This suggests that the components are not separate entities but are interlinked. Therefore, Linn and Peterson oversimplified categorizing spatial ability. Moreover, there are a variety of tasks used to test spatial ability which differ in the ways they measure it. For example, the Mental Rotation Test (Vandenberg and Kuse, 1978) measures the ability to mentally rotate 3-dimensional objects whereas the Card Rotation Test (French, Ekstrom and Price, 1976) measures the ability for 2-dimensional orientation and rotation. These problems are issues when determining whether or not sex-related differences in spatial ability exist as it likely that results vary depending on how researchers define and operationalise “spatial ability.”
Across the cognitive literature, the category that displays the largest sex difference within spatial ability is mental rotation (Linn and Peterson, 1985). Vandenberg and Kuse (1978) administered the mental rotation test and found males performed significantly better than females. The test had good reliability and validity which suggests that the findings can be trusted, to an extent. Moreover, the findings are consistent with other literature; between 1975 and 1992, the magnitude of sex differences on the mental rotation test remained stable (Masters & Sanders, 1993) and on 3D versions of mental rotation tasks, the difference was still close to one standard deviation (Mackintosh and Bennett, 2005, cited in Kaufman, 2007). This suggests that sex differences in mental rotation tasks are consistent and replicable, supporting the argument that there are sex-related differences in elements of spatial ability, specifically in mental rotation.
Vandenberg and Kuse (1978) implied that sex differences could be due to strategic differences in completing spatial tasks. They stated women reported having difficulty solving items verbally in mental rotation compared to other spatial tests, suggesting the reason why sex differences favouring males are more pronounced in mental rotation tests is because females attempt a verbal strategy whereas males do not. Although, they did not investigate this further, which places limitations on the study and claim. However, Linn and Peterson (1985) supported this strategic argument as they claimed slower performance for females on mental rotation reflects a cautious tendency to double check rather than lack of ability to perform quickly. Therefore, findings of sex differences may not reflect actual differences in spatial ability but rather differences in implicit strategies, suggesting that if strategic differences are accounted for, sex differences in spatial ability could be smaller.
Moreover, other spatial tasks do not find the same significant sex-related differences as mental rotation; Hyde (1981) found that sex differences in visual-spatial ability were small and concluded that research on cognitive gender differences may produce reliable, but tiny differences. Supporting this, Linn and Peterson (1985) found no significant sex differences in spatial visualization at any point during the lifespan. However, their meta-analysis did not include studies with children younger than 13. Despite this, this suggests sex differences do not exist in all aspects of spatial ability, but rather only exists in specific sub-categories of ability, such as mental rotation. This distinction should be highlighted as generalizing that males are better than females in overall spatial ability, from studies focusing on specific spatial elements, can lead to negative stereotypes towards females and perpetuate existing stereotypes, which in turn, could affect career and subject choice.
Gender stereotypes themselves affect the magnitude of sex-related differences in spatial ability. Stereotype threat theory assumes that subjects will perform worse when reminded of their gender in tasks where the subject’s gender is expected to have lower performance. Therefore, females may do worse than males in spatial tasks as they consider themselves less capable than males. This suggests if women are led to believe they are capable, their task performance can improve. Moè (2009) found females performed as well as males in mental rotation tasks if told that females do better than males, showing that female performance in spatial tasks can improve with changes to stereotypes and beliefs about ability. This implies that sex differences in spatial abilities are due to gender stereotypes affecting performance, supporting the argument that sex differences in spatial ability exist. However, the fact that the difference can be reduced with changes to stereotypes shows women have the capacity to perform equally as well as males, which supports the argument that sex-differences do not exist, but rather differences found are a reflection of internalised stereotypes becoming a self-fulfilling prophecy.
Moe’s study could have implications on female achievement as it suggests encouragement of female ability within STEM subjects will have positive effects on performance. Moreover, it suggests sex differences are caused by environmental factors rather than biological factors. However, others argue that the effect of stereotypes are mediated by biological factors, such as sex hormones, as stereotype effects are more prominent in females with higher baseline levels of testosterone (Josephs et al., 2003). Therefore, it is not just environmental factors that cause sex-related differences in spatial abilities but biological factors have an impact too.
If a biological causation to sex differences in spatial ability exists, differences should be apparent from an early age. Geiser (2008) looked at sex differences within mental rotation in subjects aged 9 to 23, finding differences favouring males in all age groups, but interestingly, differences were robust by the age of 9. This suggests the emergence of sex differences depends on early developmental factors, implying a biological causation. However, although this study appears to support the biological argument, by the age of 9, environmental factors will have had some effect on individuals and therefore, the effect of the environment on spatial ability cannot be disregarded. Geiser also found the magnitude of sex differences in mental rotation increases as a function of age, suggesting sex differences in spatial ability have underlying biological components that are further exaggerated by differences in the environment as individuals age. However, it could be that the increase in effect size is due to cohort effects as it was a cross-sectional design, therefore, the environments older and younger participants grew up in would have been different and could have caused the differences in effect size, as opposed to sex (Geiser, 2008). Despite this, the study supports the argument that there are sex differences in aspects of spatial ability favouring males and implies that both biological and environmental factors create an overall sex difference in ability.
This idea is supported by Hausmann (2008) who found that males performed better than females on spatial tasks and testosterone levels were higher in males when gender stereotypes were activated, compared to a control condition, suggesting that testosterone modulates performance of stereotype-activated cognitive tasks. However, the results are correlational as it could be that stereotype activation leads to better performance which causes the increase in testosterone levels. Therefore, the study did not directly show testosterone levels increased as a result of gender stereotype activation but rather signified that sex differences in spatial ability exist and are neither ‘biological’ or ‘environmental’ as previously debated but are caused by an interaction between the two factors.
Overall, there is convincing evidence of sex-related differences in specific spatial abilities, such as mental rotation. However, it is difficult to state that males have better overall spatial ability as significant differences are not found in all sub-categories of spatial ability. Furthermore, it could be that implicit factors such as strategic differences and gender stereotypes cause the appearance of sex differences but actually, both sexes have the capacity to perform just as well as each other, suggesting sex differences are not fixed. Although the causation of apparent sex differences has not been found, the most convincing argument is that differences derive from an interaction between biological and environmental factors. Crucially, generalizations cannot apply to every individual which means that when applying the idea of sex differences in spatial ability to the real world, it is imperative to assess individual ability and not assume that males have better spatial ability than females.