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Twenty males participated in a 2-month study examining the relationship between 8 a.m. plasma testosterone levels and orgasmic frequency. Within subjects, higher levels of testosterone are associated with periods of sexual activity. Over subjects, however, the direction of the relationship is reversed. Mean testosterone levels were higher for sexually less active individuals.

Adolescence in humans and nonhuman primates is a time when extensive changes occur in physiological and biochemical systems and behavior. The basic machinery of these neuroendocrine coordinations of puberty is of ancient origin and is essentially common to all mammalian species. Its operation can be modified, however, by environmental and social influences. Indeed, in humans, historically recent events have drastically changed the experience of adolescence, in some ways making it more difficult than ever before.

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