Steven Crane Compiled Section Handouts. Human Behavioral Biology 2012

Androgens also present (at 5% the level of males), involved in sexual motivation.

What does Testosterone (T) have to do with male sexual behavior? How do we know?

• Castration (no T) reduces sexual behavior, but it doesn't go down to 0. Replacing T at 10%, 100%, or even 200% the original levels causes sexual behavior to come back at the same level. Only with 1000% T way above normal physiological levels do we get an increase in sexual behavior.

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  When castrated, animals exhibit amounts of sexual behavior proportional to their pre-castration levels showing that sexual behavior is also determined by the environment and experience, not just T.
  
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  It doesn't initiate neuronal action, testosterone potentiates the effects of other excitatory stimuli.
  

How do we go about having seasonal matings? Why would we?

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  How: use melatonin. A hormone whose release is inhibited by light exposure. When day lengths are increasing, you're approaching summer; when decreasing (one day compared to the next), you're approaching winter.
  
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  Why: want to give birth during fertile spring/summer times when offspring can survive best.
  
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  Who: depends on gestation period. If 2 month gestation period then melatonin stimulates reproduction (you have a lot of melatonin in the winter, just before spring birth). If 6 month gestation period then melatonin inhibits reproduction.
  

How Early Environment Affects Sexual Behavior

What happens to socially isolated primates' sexual behavior?

• Can still do it, just don't know the right contexts.

What social imprinting happens in human children?

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  You learn who the appropriate targets for sexual behavior are.
  
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  Kibbutz studies show us that's how we "learn" who our siblings are.
  

What role does early environment play in the development of homosexuality?

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  No evidence that it has any role. "neurotic homosexuality" caused by mothers and "absent father" theories haven't held up to scientific scrutiny.