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Research into the existence of sex differences in visual cognition and related areas has been extensively reviewed in the past 20 years (Archer & Lloyd, 1985; Fausto-Sterling, 1992; Halpern, 1992; Hyde, Fennema & Ryan, 1990; Linn & Petersen, 1985; Maccoby & Jacklin, 1974; McGee, 1979; Newcombe, 1982; Tracy, 1987). The general conclusion of such reviews suggests that visuo-spatial performance appears to differ significantly between the sexes (though see Fausto-Sterling, 1992, for an alternative interpretation). Figure 1 indicates the typical pattern of results in mental rotation task performance for females and males, males typically achieving significantly higher scores. (Figure 1 omitted)
While the conventional emphasis has been made on a comparison of the two sample means (female vs. male) it is apparent from the figure that there is considerable variation in performance within the sexes and extensive overlap between the two distributions. Archer (1987) and Halpern (1992) have argued for the use of effect size in the discussion of results in order to complement significance levels and gain some indication of the extent of variance in the data which can be explained by the variable of interest. In Fig. 1 the effect size, d, associated with sex, is approximately 0.94. This is typical of the effect size found in studies employing 3-D mental rotation tasks (Halpern, 1992).
Much of this research has attempted to establish the extent to which biological factors underlie such differences. Thus, McGee (1979) considers issues such as genetic endowment, handedness and cerebral lateralization. (See also Annett, 1992 & McKeever, 1986, for a discussion of putative genetic factors underlying spatial ability.) The relevance of cerebral lateralization has also been identified by Newcombe, Dubas & Baenninger 1989. Nyborg (1988) has suggested that it is the level of estradiol that underlies the difference in visuo-spatial performance between the two sexes. Research indicating menstrual cycle impacts upon spatial performance would also support the importance of oestrogen levels, e.g. Hampson & Kimura, 1988 (see Ho, Gilger & Brink, 1986, for a qualification of this argument). Findings such as these have led some reviewers such as McGuinness (1985), Ruddisill & Morrison (1989) and Kimura (1992) to conclude that neuro-anatomical differences may account for sex differences in visuo-spatial performance and the mathematics skills which might depend upon these processes.