Serum Free Testosterone and Estradiol Levels in Perceptual-Verbal and Spatial Abilities; Differences in Sex and Hand Preference

Cognitive sex differences have been demonstrated in humans: men usually outperform women on spatial ability (Linn & Peterson, 1985; Gladue et al., 1990; Mann et al., 1990; Gouchie & Kimura, 1991; Gladue & Bailey, 1995; Halpern & Tan, 2001; Tan et al., 2003a, b; Herlitz & Lovén, 2009); women outperform men on verbal tasks (Hyde & Linn, 1988; Mann et al., 1990; Halpern & Tan, 2001; Tan et al., 2003a, 2003b; Herlitz & Lovén, 2009). The sex hormones were thought to be responsible for the observed sex differences in cognitive abilities, but the available scientific literature does not provide any generally acceptable conclusion on this topic. For instance, testosterone has been reported to be beneficial for visuospatial ability in men (Hier & Crowly, 1982; Gordon & Lee, 1986; Christiansen & Knussmann, 1987; Tan, 1990a, b; Tan & Akgun, 1992; Christiansen, 1993; Janowsky et al., 1994; Van Goozen et al., 1994; Van Goozen et al., 1995; Tan & Tan, 1998; Barrett-Connor et al., 1999a; Silverman et al., 1999; Aleman et al., 2001; Kutlu et al., 2001; Kenny et al., 2002; Yaffe et al., 2002; Azurmendi et al., 2005), and women (Shute et al., 1983; Resnick et al., 1986; McKeever, 1987; Gouchie & Kimura, 1991; Van Goozen et al., 1995; Moffat & Hampson, 1996; Barrett-Connor et al., 1999b; Celec et al., 2002; Ostatnikova, et al., 2002). On the other hand, testosterone has also been reported as having no benefit for spatial ability in either men or women (Shute et al., 1983; Gouchie & Kimura, 1991; Moffat & Hampson, 1996; Van Goozen et al., 1995). Contrarily, some authors did not accept any significant association between testosterone and spatial cognition (McKeever et al., 1987; Kampen & Sherwin, 1996; Herlitz & Lovén, 2009). An inverse U-shaped relation between testosterone and spatial cognition was also reported, that is, the optimal performance was found in moderately high levels of testosterone (Shute et al., 1983; Gouchie & Kimura, 1991; Moffat & Hampson, 1996; Alexander et al., 1998; Neave, et al., 1999). With regard to handedness, significant relationships have been found between testosterone and spatial ability in right-handers, but not in left-handers (Moffat & Hampson, 1996). Verbal abilities have also been studied in relation to sex-hormone concentrations in men and women. Some authors could not demonstrate any significant association between testosterone and verbal tasks (Gordon & Lee, 1986; Gouchie & Kimura, 1991; Neave, et al., 1999; Herlitz & Lovén, 2009), but others reported beneficial effects of testosterone on verbal ability (Cherrier, 1999; Alexander et al., 1998), but detrimental influence of androgen levels