Dissociations of Face and Object Recognition in Developmental Prosopagnosia

Abstract

Neuropsychological studies with patients suffering from prosopagnosia have provided the main evidence for the hypothesis that the recognition of faces and objects rely on distinct mechanisms. Yet doubts remain, and it has been argued that no case demonstrating an unequivocal dissociation between face and object recognition exists due in part to the lack of appropriate response time measurements (Gauthier et al., 1999). We tested seven developmental prosopagnosics to measure their accuracy and reaction times with multiple tests of face recognition and compared this with a larger battery of object recognition tests. For our systematic comparison, we used an old/new recognition memory paradigm involving memory tests for cars, tools, guns, horses, natural scenes, and houses in addition to two separate tests for faces. Developmental prosopagnosic subjects performed very poorly with the face memory tests as expected. Four of the seven prosopagnosics showed a very strong dissociation between the face and object tests. Systematic comparison of reaction time measurements for all tests indicates that the dissociations cannot be accounted for by differences in reaction times. Contrary to an account based on speed accuracy tradeoffs, prosopagnosics were systematically faster in nonface tests than in face tests. Thus, our findings demonstrate that face and nonface recognition can dissociate over a wide range of testing conditions. This is further support for the hypothesis that face and nonface recognition relies on separate mechanisms and that developmental prosopagnosia constitutes a disorder separate from developmental agnosia.

Impaired face and body perception in developmental prosopagnosia

“…The results suggests that anomalies in the initial visual processing stages in infancy may hinder the acquisition of configural processing skills and may gradually translate as face recognition deficits in adulthood. Previous studies have reported that in addition to face recognition, deficits in prosopagnosia may extend to nonface objects, although so far a close comparison as now done here has not been undertaken (4,8,10,16,20,33,56). In line with these studies, our results suggest that configural processing is impaired for faces and bodies.…”

“…Each score is 2 SD below the mean of the control group, (except the score of G.R. on the easy version), which may relate to face and object recognition problems in developmental prosopagnosia as found in previous studies (10,33). Table 1 shows results of the face recognition tests.…”

“…For some prosopagnosic cases, the N170 did not show the characteristic increased amplitude for faces as compared with objects (28-31), whereas for other cases an increase of the N170 for faces relative to objects was reported much as in normal subjects (31,32). This lack of consistency may be related to the heterogeneous nature of developmental disorders like prosopagnosia and is in line with mixed results obtained in behavioral (9,20,33) and functional MRI studies (34)(35)(36), mostly of single patients.…”

Psychosocial consequences of developmental prosopagnosia: A problem of recognition

“…The average for participants on the CFMT II was 36.5 (S.D.=6.3). These means are very similar to the mean of 37.0 (S.D.=6.1) for all DP scores on the original CFMT in published studies [3,7,[16][17][18][19]. To ensure that participants with prosopagnosia acquired in adulthood were excluded, our first interview question was 'How did you come to realize you had prosopagnosia?…”

“…The case histories and self-reports of some people with prosopagnosia (both developmental and acquired) suggest that it can have a severe impact on people's lives, resulting in avoidance of social interaction, problems with interpersonal relations, damage to career, and even depression [1,[6][7][8][9]. Since DP interferes with social interaction it might predispose some people to develop social anxiety disorder, which is characterized by fear and avoidance of social situations which have the potential to cause embarrassment or humiliation [10,11].…”