Abstrakt

Time course of face perception measured by differential Pavlovian conditioning

Yusuke Nakashima, Yoichi Sugita

We investigated the time course of face perception by using differential Pavlovian conditioning. Face and non-face images were used as conditioned stimuli (CSs). Some stimuli (CS+) were always followed by the unconditioned stimulus (UCS), whereas others (CS−) were presented alone. The UCS was an air puff delivered to the right eye. We measured the time necessary for discrimination between the faces by manipulating stimulus onset asynchrony (SOA) between the CS and the UCS. For discrimination between a face and a non-face object, successful differential conditioning was observed for short SOA. However, for discrimination between individual faces, differential conditioning was observed only when SOA was long. Moreover, much longer SOA was needed for discrimination between faces differing only in facial features or spacing. These results indicate that the time course of face processing stages can be observed by manipulating the SOA in differential Pavlovian conditioning. The time necessary for the discrimination measured by conditioning was shorter than that measured psychophysically, suggesting that conditioned responses are made through fewer processing steps than the subjective reporting in psychophysical measurement.