Abstract
There is accumulating evidence suggesting that a central deficit in developmental prosopagnosia (DP), a disorder characterized by profound and 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 or reduced global bias compared with controls. However, it has not been established what gives rise to this altered processing bias. Is it a reduced global precedence effect, changes in susceptibility to interference effects or both? By analyzing the performance of 10 individuals with DP in Navon’s paradigm we find evidence of a reduced global precedence effect: The DPs are slower than controls to process global but not local shape information. Importantly, and in contrast to previous studies, we demonstrate that the DPs perform normally in a comprehensive test of visual attention, showing normal: visual short-term memory capacity, speed of visual processing, efficiency of top-down selectivity, and allocation of attentional resources. Hence, we conclude that the reduced global precedence effect reflects a perceptual rather than an attentional deficit. We further show that this reduced global precedence effect correlates both with the DPs’ face recognition abilities, as well as their ability to recognize degraded (non-face) objects. We suggest that the DPs’ impaired performance in all three domains (Navon, face and object recognition) may be related to the same dysfunction; delayed derivation of global relative to local shape information.
Highlights
Developmental prosopagnosia (DP) is a disorder characterized by profound and lifelong difficulties with face recognition in the absence of any sensory or intellectual deficits or known brain injury [1]
If we find no evidence of restricted allocation of attention in the developmental prosopagnosia (DP) group, this will suggest that the impaired derivation of global shape information reflects a perceptual rather than an attentional deficit
Given are the p-values associated with the difference between DPs and Controls for the Theory of Visual Attention (TVA)-parameter estimates.Units for the individual parameters are t0, C, K, α ranges from perfect selection at 0 to non-selectivity at 1, windex ranges from complete rightward bias at 0 to complete leftward bias at 1 with 0.5 indicating equal weighting between the two visual fields, SDweights ranges from pffiffiffiffiffiffiffi equal weighting on all six locations at 0 to all weight on a single location at 1=6
Summary
Developmental prosopagnosia (DP) is a disorder characterized by profound and lifelong difficulties with face recognition in the absence of any sensory or intellectual deficits or known brain injury [1]. Whether the disorder is selective for faces, or whether it may affect the visual processing of other categories of objects beside faces, is debated [2,3,4]. What is a precondition for the diagnosis, is that everyday recognition of faces is far more affected than recognition of other types of objects. Individuals with DP can report numerous examples of experiences in which they were unable to recognize individuals after exposure that would lead to recognition success in neurologically typical people [1]. In our experience, they do not report similar problems with other categories of objects.
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