Laterality for facial expressions: does the sex of the subject interact with the sex of the stimulus face?

Seventy right-handed subjects (35 males and 35 females) were shown lateralized pictures of negative, neutral, and positive facial emotional expressions. For each emotional category, half of the pictures were of a male face showing the emotion, half were of a female face. The pictures were shown in the left visual half-field for half of the trials and in the right half-field for the other half of the trials. The question addressed was whether the sex of the stimulus face interacts with the sex of the subject for hemisphere differences in perception of facial emotions. Response accuracy and reaction time were measured. The pictures were shown from a slide projector with a high-speed shutter mounted to the lens to allow for tachistoscopic presentations. The results showed that the right hemisphere was more accurate and faster than the left in recognizing the stimulus faces, and that positive emotions were overall more easily recognized. The lack of a significant interaction between sex of the stimulus and sex of the subject indicates that these two factors are not interrelated or confounded in laterality research.