Target and mask preview effects in object substitution masking M Pilling |
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Psychology, Oxford Brookes University, United Kingdom
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| Object substitution masking (OSM) is a form of masking in which a briefly presented target present in a stimulus array is rendered imperceptible by a sparse mask -typically consisting of just four surrounding dots which trail the offset of the target. Recent accounts suggest that OSM occurs when the visual system fails to individuate target and mask at the object token level of description. Previous studies have indicated that OSM is reduced, or even eliminated, when a preview is given of the target or mask elements before onset of the stimulus array. Here target and mask preview are compared directly and found to have largely symmetrical effects, consistent with the object token explanation. However, curiously, OSM is not entirely eliminated even with a 650 ms preview of target or mask elements. Interestingly, the amount of unmasking arising from target/mask preview was essentially the same irrespective of stimulus array size –varied between 4 and 12 items. This finding indicates that the visual system has a high capacity to represent object token elements exceeding at least 12 items. |
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