This study investigates neural responses to neutral, happy, and sad facial expressions using a "face in the crowd" task. The study hypothesizes that amygdala activation will differ for target vs non-target emotional stimuli and between emotion types. It also hypothesizes differences in heart rate between male and female faces. The experimental setup involves participants detecting matches/mismatches among facial arrays within task blocks, followed by fixation blocks. Brain activity will be analyzed for visual and emotion regions like the amygdala, predicting greater amygdala activity for faces vs fixation and targets vs non-targets, as well as for sad faces.