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Michael Mack, Thomas Palmeri; Uncovering the time course of categorization with object-substitution masking. Journal of Vision 2012;12(9):811. doi: 10.1167/12.9.811.
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© ARVO (1962-2015); The Authors (2016-present)
Visual object categorization maps visual representations onto category names. It is a process that takes time with some categorizations taking more time than others. The classic finding of a basic-level ("dog") advantage in categorization (Rosch et al., 1976) has been challenged by the finding of a superordinate-level ("animal") advantage during ultra-rapid categorization (Macé et al., 2009). Recent work attempting to reconcile these findings (Mack & Palmeri, 2011a, 2011b) proposes that weak perceptual evidence of an object’s superordinate category is available early in the time course of categorization. The current study investigated this proposal by uncovering critical points in the latent time course of categorization with an object-substitution masking (OSM) paradigm (Di Lollo et al., 2000). The extent of an OSM effect on categorization indicates not only the nature of categorization processes, but also when these processes occur. Participants performed category verification of superordinate (animal vs. vehicle) and basic (dog vs. bird, car vs. plane) target objects among two object distractors. An OSM mask consisting of four black squares surrounded the target object and vanished after the brief presentation of the stimuli or after a 50ms delay. Basic-level categorization was significantly impaired with the mask delay, while superordinate categorization performance was relatively spared. A parametric manipulation of mask delay (0-125ms) showed further evidence of temporal differences between superordinate and basic-level categorization. While a masking effect was evident in both conditions, superordinate categorization was impaired with a shorter mask delay (25ms) than basic-level categorization (33ms). This novel use of object-substitution masking suggests that categorization of real-world objects may depend on iterative sampling of visual information. The timing of the OSM effects reveals the latent time course of visual object categorization: perceptual evidence for the animal in a scene is available quickly and faster than evidence for the bird.
Meeting abstract presented at VSS 2012
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