A multitude of research supports that fluctuations in fertility and hormonal shifts in normally cycling females influence changes in female sexual strategies, preferences, and desires across the menstrual cycle. Evolutionary theory posits that in order to maximize reproductive benefits, near ovulation female responses to sexual stimuli alter and cues of sex are more appealing. The post-auricular reflex (PAR) is a psychophysiological reaction that has been linked to motivation and reward, emotion, and appetitive responding. The PAR responds to pleasant stimuli, including stimuli that are relevant to evolutionary themes. The purpose of the current study was to explore the nature of the post-auricular reflex, and in particular, to examine potential shifts in motivation and reward processing of sexual and emotional stimuli across the female menstrual cycle. Ovulation blunted PAR responses to non-erotic categories in normally cycling females, while responses to erotica did not significantly decrease across phases of the menstrual cycle. Ovulation was also found to affect female self-report of sexual desire. These shifts were not seen in females using hormonal birth control. The study results suggest that ovulation shifts female priorities towards reproduction by increasing desire and also decreasing motivations for non-mate-relevant activities. The study also demonstrates the need for greater investigation of the PAR and the appetitive responding system. / Psychology