On the organization of face memory

When two 3D objects are sequentially presented, the time to judge whether they are identical is proportional to the angle between the objects implying that humans might rotate mental images of objects for identification. Similar effects were also reported for faces. In the present study we investigated the effects of familiarity of faces on reaction times in two cognitive tasks. (1) Delayed matching-to-sample task based on face identification (I-DMS task): a sample was followed by a test (match or nonmatch) after a delay. The stimuli were pictures of people's faces that were either unfamiliar or familiar to the subject. The subjects were required to identify the same person instructed in the sample; match consisted of seven images of the person viewed from seven different angles. We found that reaction times were proportional to the angle between sample and match in the I-DMS task for both unfamiliar and familiar faces, although reaction times were longer for unfamiliar faces. (2) Pair association task based on face identification (I-PA task): subjects learned four paired associates in advance of test (pre-learning): the pair consisted of a neutral geometric pattern and a human face viewed from −45° or +45° (obligue views). In the test, a stimuli pair was sequentially presented and the subject was required to judge whether the pair was correct or not. The correct pair consisted of the pattern and faces of the person who was associated with the pattern in the pre-learning, which could be one of six images of the person viewed from six different angles. In the I-PA task we found that reaction times were influenced by the pre-learning for both unfamiliar and familiar faces. For unfamiliar faces but not for familiar faces, pre-learning shortened reaction time for the view opposite to the view that was encoded in the pre-learning. Taken together, these results indicated that representations were different between unfamiliar and familiar faces. As faces become familiar from unfamiliar, transition of representations might take place.