From an evolutionary perspective, the reason is obvious—perpetuation of the spe
From an evolutionary perspective, the reason is obvious—perpetuation of the species. Sexual behaviour in humans, however, involves much more than reproduction. This section provides an overview of research that has been conducted on human sexual behaviour and motivation. This section will close with a discussion of issues related to gender and sexual orientation.
Physiological Mechanisms of Sexual Behaviour and Motivation
Much of what we know about the physiological mechanisms that underlie sexual behaviour and motivation comes from animal research. As you’ve learned, the hypothalamus plays an important role in motivated behaviours, and sex is no exception. In fact, lesions to an area of the hypothalamus called the medial preoptic area completely disrupt a male rat’s ability to engage in sexual behaviour. Surprisingly, medial preoptic lesions do not change how hard a male rat is willing to work to gain access to a sexually receptive female (Figure EM.14). This suggests that the ability to engage in sexual behaviour and the motivation to do so may be mediated by neural systems distinct from one another. What is interesting, is that the medial preoptic area in males is larger and contains more cells, compared to females.
Although human sexual behaviour is much more complex than that seen in rats, some parallels between animals and humans can be drawn from this research. The worldwide popularity of drugs used to treat erectile dysfunction (Conrad, 2005) speaks to the fact that sexual motivation and the ability to engage in sexual behaviour can also be dissociated in humans. Moreover, disorders that involve abnormal hypothalamic function are often associated with hypogonadism (reduced function of the gonads) and reduced sexual function (e.g., Prader-Willi syndrome). Given the hypothalamus’s role in endocrine function, it is not surprising that hormones secreted by the endocrine system also play important roles in sexual motivation and behaviour. For example, many animals show no sign of sexual motivation in the absence of the appropriate combination of sex hormones from their gonads. While this is not the case for humans, there is considerable evidence that sexual motivation for all humans varies as a function of circulating testosterone levels (Bhasin, Enzlin, Coviello, & Basson, 2007; Carter, 1992; Sherwin, 1988).
Kinsey’s Research
Before the late 1940s, access to reliable, empirically-based information on sex was limited. Physicians were considered authorities on all issues related to sex, despite the fact that they had little to no training in these issues, and it is likely that most of what people knew about sex had been learned either through their own experiences or by talking with their peers. Convinced that people would benefit from a more open dialogue on issues related to human sexuality, Dr. Alfred Kinsey of Indiana University initiated large-scale survey research on the topic (Figure EM.16). The results of some of these efforts were pub