A whole face is more than the sum of its halves: Interactive processing in face perception

Facial information is processed interactively. Yet, such interactive processing has been examined for discrimination of face parts rather than complete faces. Here we assess interactive processing using a novel paradigm in which subjects discriminate complete faces. Face stimuli, which comprise unilateral facial information (hemifaces) or bilateral facial information from one face (consistent) or two different faces (inconsistent), are shown centrally in a face-matching task. If each half of a complete face is processed independently, accuracy for complete faces can be predicted by the union of accuracies for right and left hemifaces. However, accuracy exceeded this independence prediction for consistent faces (facilitation) and fell below the prediction for inconsistent faces (interference). These effects were reduced or absent for inverted faces. Our findings are consistent with reports of stronger interactive processing for upright than for inverted faces and they quantify effects of interactive processing on the discrimination of complete faces.