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Jonathan S. Cant, Melvyn A. Goodale; Interaction between outline shape and surface-property processing in object recognition. Journal of Vision 2008;8(6):520. doi: https://doi.org/10.1167/8.6.520.
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We have previously shown that the processing of shape and the processing of surface properties (i.e. colour and texture) engage anatomically distinct regions of occipito-temporal cortex (Cant & Goodale, 2007). But establishing that distinct cortical regions process shape and surface properties does not imply that these regions function independently during object recognition. To establish true functional independence, it is necessary to use a sensitive behavioural measure which assesses whether the processing of one attribute interferes with the processing of another. In this regard, we used a behavioural paradigm known as Garner's speeded-classification task to assess whether the processing of shape interferes with the processing of surface properties (Cant et al., Perception, in press). We showed that varying the surface properties of objects does not interfere with shape judgments and vice versa. These results suggest that the mechanisms underlying form and surface properties can function independently during object recognition - at least under conditions where perceiving the surface properties means perceiving the material from which the objects were made. But it is also possible for surface properties (such as texture gradients) to provide cues to an object's form. In the present study, we varied surface properties that contribute to the perception of object shape and hypothesized this would interfere with judgments about the width of the objects. In contrast, we predicted that varying the width of the objects would not interfere with surface-property judgments. This is precisely what we found using Garner's speeded-classification task. These results suggest that in some situations the outline shape and the surface properties of objects cannot be processed independently because they share common processing resources. In other situations (where surface properties do not contribute to the perception of shape) these object attributes do not share common processing resources and may indeed be processed by distinct cortical regions.
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