Walsh & Hoyt: Apperceptive Prosopagnosia

In apperceptive prosopagnosia, patients cannot form an accurate picture of the face before them. In the past, this diagnosis has usually relied upon indirect deductions from performance on other visual tests not involving faces. These include overlapping figures, silhouettes, Gestalt completion tests, and global texture or moire patterns. However, it is far from proven that the mechanisms probed by such tests are truly related to normal face recognition. Somewhat closer is the use of unfamiliar face-matching tests like the BFRT. Failure to match faces seen in different views or lighting may indicate a problem in extracting relevant facial structure. Though more logically appealing, this argument is problematic because the BFRT can also be failed by patients without prosopagnosia. This raises the possibility that performance on the BFRT depends upon facial information irrelevant to face recognition. (Although it seems counterintuitive that subjects would identify unfamiliar faces using criteria they do not apply to familiar faces, there is evidence that different strategies may indeed be used. For example, the internal facial features appear to play a greater role in recognizing familiar faces than in identifying unfamiliar ones. Alternatively, prosopagnosia may require additional defects besides those that lead to poor BFRT performance.