Abstract
We report converging evidence that higher stages of the visual system are critically required for the whole to become more than the sum of its parts by studying patient DF with visual agnosia using a configural superiority paradigm. We demonstrate a clear dissociation between this patient and normal controls such that she could more easily report information about parts, demonstrating a striking reversal of the normal configural superiority effect. Furthermore, by comparing DF's performance to earlier neuroimaging and novel modeling work, we found a compelling consistency between her performance and representations in the early visual areas, which are spared in this patient. The reversed pattern of performance in this patient highlights that in some cases visual Gestalts do not emerge early on without processing in higher visual areas. More broadly, this study demonstrates how neuropsychological patients can be used to unmask representations maintained at early stages of processing.
Highlights
1 Main text How do wholes become different from the sum of their parts? This classic Gestalt question is elegantly brought to experimental life in a simple configural superiority paradigm devised by James Pomerantz and colleagues (Pomerantz, Sager, & Stoever, 1977)
Kubilius et al (2011) used multi-voxel pattern analysis (MVPA) techniques in a functional magnetic resonance imaging experiment to demonstrate that patterns of activation evoked by this paradigm revealed an advantage for the configural “whole” condition only in the higher visual areas lateral occipital (LO) and posterior fusiform
Like the primary visual cortex (V1), showed the opposite, i.e., a better discrimination in the isolated “part” condition. This result potentially demonstrates that configural information exists neither in the stimulus nor in its representation in early visual areas—Gestalts only become different from the sum of their parts at higher stages of processing
Summary
How do wholes become different from the sum of their parts? This classic Gestalt question is elegantly brought to experimental life in a simple configural superiority paradigm devised by James Pomerantz and colleagues (Pomerantz, Sager, & Stoever, 1977). Like the primary visual cortex (V1), showed the opposite, i.e., a better discrimination in the isolated “part” condition This result potentially demonstrates that configural information exists neither in the stimulus nor in its representation in early visual areas—Gestalts only become different from the sum of their parts at higher stages of processing. DF’s reaction times revealed the same reversal, with much faster performance in the isolated line condition, though overall DF’s reaction times were much slower than healthy controls (Figure 4) This result is consistent with the hypothesis that early visual cortex is not sufficient to produce compelling Gestalt representations. Our results highlight how neuropsychological patients can be used to test computational models by “unmasking” the representations at earlier stages of processing (Mannan, Kennard, & Husain, 2009; Ossandón et al, 2012)
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