Facial stimuli were photographs of young adults of European descent, head shot only, on a black background with facial features unobstructed by hair from the eyebrows down (Figure 1). The photos were originally used by Marinkovic & Halgren (1998) and were unfamiliar people to this study’s subjects. The volunteers were instructed on how to express sad, neutral (no emotion) or happy expressions and practiced before photos were taken. The photographs used were a subset selected based on a 95% inter-rated consistency score from 25 judges for emotional expression type: happy, neutral or sad. Stimuli were presented on a computer monitor using the E-prime software system (Psychology Software Tools, Inc., Pittsburgh, PA) with a horizontal and vertical visual angle of approximately 12.4° × 15.7°. Images of emotional facial expressions were presented on a black screen for 2000 ms, or until the subject pressed a response key, with a 2000 ms ISI consisting of a completely black screen. Less than 2% of trials were missed and advanced by computer.
