Understanding Psychology (10th Ed)

 BIOLOGICAL AND EVOLUTIONARY FACTORS 
Do differences between male and female brains underlie sex and gender differences? 
This intriguing hypothesis has been put forward by some psychologists studying 
brain structure and functioning. For instance, girls who were exposed before birth to 
unusually high levels of androgen , a male hormone, because their mothers acciden-
tally took a drug containing that hormone while pregnant preferred different toys 
from those preferred by girls not exposed to androgens. Specifi cally, they were more 
likely to play with toys that boys stereotypically prefer (such as cars) and less likely 
to play with toys girls stereotypically prefer (such as dolls). Other research, discussed 
in Applying Psychology in the 21 st Century, supports this fi nding. It is possible that 
exposure to particular hormones prior to birth may affect brain development, making 
children favor toys that involve certain kinds of skills, such as those related to spatial 
abilities (Mealey, 2000; Hines et al., 2002, Fink et al., 2007; Hines & Alexander, 2008).
Similarly, some evidence suggests that women perform better on tasks involving 
verbal skill and muscular coordination during periods when their production of the 
female sex hormone estrogen is relatively high compared with periods when it is low. 
In contrast, they perform better on tasks involving spatial relationships when the 
estrogen level is relatively low (Kimura, 1999; Rosenberg & Park, 2002). 
Some psychologists argue that evolutionary forces lead to certain differences between 
men’s and women’s behavior. For example, David Buss and colleagues point to differ-
ences in the nature of jealousy between men and women. Men are more jealous in cases 
of sexual infi delity than in cases of emotional infi delity; women are more jealous in cases 
of emotional infi delity than in cases of sexual infi delity (Buss et al., 1992; Buss, 2003). 
According to Buss’s controversial explanation, the root cause for the differences 
in jealousy lies in the evolutionary implications of sexual versus emotional infi delity 
for men and women. He argues that for males, sexual infi delity represents a threat 
to their ability to ensure that their children are actually their own (and are the ones 
who have inherited their genes). In contrast, females have no doubt that a child they 
carry through pregnancy is their own. However, their major concern is ensuring the 
male’s protection and support during child rearing. Thus, to females, maintaining 
males’ emotional attachment is crucial. 
Psychologists relying on the evolutionary approach also argue that similarities 
in the division of labor between men and women across different cultures suggest 
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that sex differences are due to evolutionary factors. They argue that even in very 
different types of cultures, men tend to be more aggressive, competitive, and prone 
to taking risks than women are—traits that had an evolutionary advantage (Mealey, 
2000; Buss, 2003; Chang & Geary, 2007). 
However, many critics question the assumptions of the evolutionary approach. 
Rather than assuming that the differences are due to evolutionary forces, some psy-
chologists suggest that differences in males’ and females’ beliefs about the meaning 
of infi delity are the actual cause of their jealousy differences. For instance, men may 
believe that women have sex only when they are in love. Consequently, sexual infi -
delity may be seen as a sign that a woman is in love with another man and may 
produce more jealousy than emotional infi delity alone would. In contrast, women