Sexual dimorphism has fascinated Psychologists throughout history and continues to be a point of discussion. Research has established that sex differences in some spatial tasks exist. However, the extent to the sex differences has been widely over-exaggerated by laypersons, the media and researchers. Furthermore, a complete understanding of why sex-related differences occur has not been agreed upon; some argue biological causes, some argue social causes, whilst others argue a psychobiosocial approach; combining both biological and environmental factors. Therefore, this essay aims to describe what evidence there is for sex differences in spatial ability and evaluate the extent to which these studies and their findings can be relied upon as findings of sex differences can have huge real-world 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) only defined a single spatial visualization factor, whereas others argue that spatial ability is made up of different components; Linn and Peterson (1985) defined three categories of spatial tasks 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 completely separate entities but are in some ways interlinked. Therefore, Linn and Peterson oversimplified the categorization of spatial ability. This definitional problem is therefore an issue when determining whether or not sex-related differences in spatial ability exist as it could be that results differ depending on how researchers categorize and operationalize “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) found males performed significantly better than females on the mental rotation test. The study had good reliability and validity which suggests that the sex differences are real and the findings can be trusted to an extent. Moreover, the findings are consistent with other literature; between 1975 and 1992, the magnitude of the sex difference 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 emphasizes that sex differences in mental rotation tasks are consistent and replicable across time and across different versions of the task, supporting the argument that there are sex-related differences favouring males in elements of spatial ability, specifically in mental rotation.
However, other spatial tasks do not find the same significant sex-related differences as mental rotation; Hyde (1981) found that gender 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, suggesting sex differences do not exist in all aspects of spatial ability, but rather differences may only be apparent in specific sub-categories of ability, such as mental rotation. This distinction should be made apparent 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 could potentially enhance stereotypes that males are better at science and mathematics (as these subjects involve higher spatial ability) which in turn, could affect female subject and career choice. Therefore, this highlights the possible effects that research into sex-related differences in spatial ability can have on subject-choice, job allocation and gender stereotypes.
Gender stereotypes 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 compared to males. This suggests if women are led to believe they are capable, their task performance can improve (Moè, 2009). Moè found that females performed as well as males in the mental rotation task if told that females do better than males and performed worse when told men do better, showing that female performance in spatial tasks can increase with changes to stereotypes and positive beliefs about ability. This implies that sex differences in spatial abilities are due to gender stereotypes affecting performance. This could have real-world implications on female achievement and career choice as it suggests that encouragement of females into subjects such as mathematics and science will have positive effects on performance. Moreover, this suggests sex differences are caused by environmental factors rather than biological differences between the sexes. However, others argue that the effect of stereotypes is mediated by biological factors, such as sex hormones, as stereotype effects are more prominent in individuals with naturally higher 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 on ability too.
If a biological causation to sex differences in spatial ability exists, the suggestion is there would be sex differences from an early age. Therefore, research investigated the effect of age on the magnitude of sex differences. 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 appeared to be robust by the age of 9. This suggests the emergence of sex differences depends on early developmental factors, implying a biological causation, such as the difference in functional brain organisation between sexes. However, although this study seems to support the biological argument, by the age of 9, environmental factors will still have had an effect on individuals and therefore, the effect of the environment on spatial ability cannot be disregarded.
Geiser (2008) also found that 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. For example, from childhood, males are said to be more involved in everyday spatial activities than females, leading to better mental rotation performance. However, the effect size found was small which shows that although there may be an increasing difference favouring males as individuals age, the difference is small. Despite this, the study suggests that both biological and environmental factors create an overall sex difference in ability. This idea is supported by Hausmann (2008) who investigated the interaction between sex hormones and gender stereotypes on cognitive performance. They found that males performed better than females on spatial tasks and that testosterone levels were higher in males when gender stereotypes were activated compared to a control condition, suggesting that testosterone modulates performance of sex-sensitive cognitive tests in males (Hausmann, 2008). 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 does not directly show testosterone levels increased as a result of gender stereotype activation but rather signifies that sex differences in spatial ability are neither ‘nature’ or ‘nurture’ as previously debated. Instead, sex differences are caused by an interaction between the two factors.
Conversely, others argue that sex differences in spatial ability are due to strategic differences in completing spatial tasks. Vandenberg and Kuse (1978) found women had 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. Supporting this strategic argument is Linn and Peterson (1985) who claimed slower performance for females on mental rotation reflects a tendency to double check rather than lack of ability to perform quickly. Therefore, findings of sex-related differences may not reflect actual differences in spatial ability but rather differences in underlying strategies, implying that if strategic differences accounted for, sex differences in spatial ability would be much smaller.
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 aspects of spatial ability, for example, spatial visualization. Furthermore, generalizations cannot apply to all individuals, therefore some females may be better than males in spatial ability. This possibility means that when applying the idea of sex differences in spatial ability to the real world, it is crucial to assess individual ability and not rely on the generalization that males are better than females. Moreover, the causation of these differences has not been agreed upon. However, the most convincing argument is that differences derive from an interaction between biological and environmental factors as opposed to the argument which tries to calculate the proportion of biological influences and environmental influences and figure out which is more prominent.
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