Sex Differences in the Organization of Behavior Patterns: Endpoint Measures Do Not Tell the Whole Story
Evelyn F. Field and Sergio M. Pellis
In 1959, Phoenix, Goy, Gerall, and Young demonstrated that the potential for either masculine or feminine sexual behavior in guinea pigs is dependent on early exposure to gonadal hormones. Males undergo masculinization of maletypical characteristics and defeminization of female-typical characteristics due to the action of gonadal hormones in early development. Postpubertally, hormones activate the expression of these sex differences. Since this early work, a number of studies using different species have replicated these findings ( Baum, 1979; Baum, Carroll, Cheffy, & Tobet, 1990), supporting the idea that gonadal hormones have an organizing effect early in development and an activating effect in adulthood. In addition, the development of sex differences between males and females has been extended beyond reproductive behavior patterns to include sexual orientation ( Adkins-Regan, 1988), spatial behavior ( Williams, Barnett, & Meck, 1990; Williams & Meck, 1991), spontaneous/exploratory activity ( Stewart & Cygan, 1980; Mead, Hargreaves, & Galea, 1996), rotational behavior ( Carlson & Glick, 1996), micturition in dogs ( Beach, 1974), and play ( Meaney & Stewart, 1981; Meaney, 1988; 1989; Pellis, Pellis, & McKenna, 1994).
Even though sex differences in mammals exist in both reproductive ( Ward, 1992) and nonreproductive behaviors ( Beatty, 1992), most sexually dimorphic behaviors are dimorphic only in the sense that one sex is more likely to perform them than the other ( Aron, Chateau, Schaeffer, & Roos, 1991; Goy & Roy, 1991). Except for some behavioral patterns that are associated with parturition, most