Testing the relationship between levels of endogenous testosterone and physiological responses to facial expressions in men: an experiment conducted by students in an undergraduate behavioral neuroscience class.

To determine if endogenous testosterone (T) is related to physiological responses to aggressive stimuli in human males, students in a behavioral neuroscience laboratory class conducted an experiment that determined if levels of salivary T in adult males are correlated with autonomic and/or somatic responses to angry facial expressions. Each student collected a saliva sample from one subject and, within 30 minutes of collecting the sample, measured heart rate (HR), skin conductance (SC), and corrugator supercilii electromyographic (EMG) responses to emotionally neutral, happy, and angry male facial expressions. Salivary T levels were analyzed by an enzyme-linked immunoassay. A significant, positive correlation was found between levels of salivary T and HR responses to angry and happy, but not neutral, male facial expressions. This laboratory experience not only provided students with the opportunity to design and conduct a scientific experiment, but it also generated preliminary data suggesting that levels of salivary T collected within 30 minutes of testing are related to autonomic responses to emotional social stimuli in humans. If verified by future experiments, this finding would be consistent with the hypothesis that fluctuations in circulating T might influence ongoing social behavior in human males by rapidly modulating autonomic responses to emotional social stimuli. The potential significance of such a general mechanism for the regulation of aggressive behavior is discussed.