Human social endocrinology research has shown that hormones are sensitive to social stimuli and may show predictable fluctuations during brief social interactions. I present an investigation of the function of potential hormonal and cognitive changes that occur during a brief social interaction by manipulating both the ecological stimuli and physiological state of male and female participants before a potential courtship opportunity. Chapter 2 examines the relationship between psychosocial stress, social interaction, and hormonal reactivity (testosterone and cortisol) in men and women, and suggests that relationship status and psychosocial stress may be important variables moderating the relationship between ecological cues of courtship and subsequent adaptive physiological responses. Chapter 3 explores how psychosocial stress and social interaction relate to cognitive performance. I found little evidence that a courtship opportunity impairs cognitive performance; instead, signs of increased stress (e.g., subjective anxiety, cortisol reactivity) actually seemed to correlate with improved cognitive performance, indicating that acute stress may increase overall attentional focus. Chapter 4 investigates the relationship between hormonal reactivity, social behavior, and stress. My data did not support the connection between testosterone reactivity and displays of courtship behavior, but did support the idea that psychosocial stress may affect the relationship between personality and courtship behavior. Further, the data support the idea that individuals who experience higher increases in cortisol after psychosocial stress may show less courtship display behavior.