There is accumulating evidence suggesting that the central deficit in developmental prosopagnosia (DP), a disorder characterized by lifelong difficulties with face recognition, concerns impaired holistic processing. Some of this evidence comes from studies using Navon's paradigm where individuals with DP show a greater local/reduced global bias compared with control subjects. However, it has not been established precisely what gives rise to this altered processing bias: Is it a reduced global precedence effect, changes in susceptibility to interference effects, or both? To examine this, we tested 10 subjects with DP and 20 matched controls on Navon's paradigm with compound letters. We also assessed visual attention and object recognition in both groups. The DP-group exhibited a reduced global precedence effect compared with the control group. They were also impaired recognizing silhouette and fragmented objects. In contrast, their visual short-term memory capacity, visual processing speed, efficiency of top-down selectivity, and spatial allocation of attentional resources were within the normal range. This suggests that the reduced global bias effect found in the DP-sample reflects a perceptual rather than an attentional deficit. To examine whether the reduction in the global precedence effect was systematically related to the face recognition impairment of the DPs we examined the correlation between the magnitude of the global precedence effect and performance on the Cambridge Face Memory Test. This yielded a positive correlation (r = .63, p = .026 one-tailed); the lower the global bias the poorer the face recognition performance. Similar relationships were observed for object recognition with silhouettes (r = .72, p = .022 one-tailed) and fragmented forms (r = .72, p = .01 one-tailed). We conclude that the DPs' impaired performance in all three domains (Navon, face and object recognition) is related to the same dysfunction; delayed derivation of global shape information.

Meeting abstract presented at VSS 2017