Classical conditioning of sexual arousal has previously been demonstrated in human males but not in females. This study explored the role of classical (Pavlovian) conditioning in the activation of genital sexual arousal in both women and men, and assessed the effects of varying conditioned stimulus (CS) duration (subliminal/conscious) and relevance (sexually relevant/irrelevant). Twenty-seven female and 29 male participants received either subliminal or conscious presentations of a photograph of either a sexually relevant (abdomen of the opposite sex) or irrelevant (gun) CS+, which was followed by the unconditioned stimulus (US-erotic film clip). A CS-, a stimulus not paired with the US, was also included in the 11 conditioning trials. Ten participants were assigned to a control group that received unpaired presentations of the CS+, CS-, and the US. Both women and men showed more evidence of conditioning to the abdomen than to the gun when the CS was presented subliminally. When consciously perceived CSs were used, however, gender differences emerged. Men again showed the expected cue-to-consequence specificity but women showed the opposite effect, that is, conditioned arousal to the sexually irrelevant rather than to the relevant CS. The latter finding may be due to increased autonomic nervous system arousal associated with the irrelevant CS (gun). Skin conductance responses indicated more general arousal to the gun than to the male abdomen in women. This is the first study to compare the effects of a subliminal and conscious CS and to find classical conditioning of sexual arousal in women.

Hagen's Defection Hypothesis (2002) predicts that a mother's age and the quality of her offspring are critical factors in determining her investment in her newborn. We tested this hypothesis using hamster races in which 113 college student participants received a hamster ("offspring") and 10 poker chips ("resources") to "invest" into the hamster based on information about the quality of the hamster and about the possibility of future races. Subjects invested the most in low quality offspring when they expected to run only one race and the least in low quality offspring when they expected more racing opportunities in the future. Offspring quality affected investment differently depending on the presence or absence of future investment opportunities and the sex of the subject. Overall, the results supported Hagen's model of parental investment and also suggest that parental investment may be explained by conscious as well as unconscious decision-making.