The role of familiarity and predictability in contour grouping M Sassi, M Demeyer, B Machilsen, T Putzeys, J Wagemans |
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Laboratory of Experimental Psychology, University of Leuven (KU Leuven), Belgium
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| Research using snake-shaped Gabor contours has shown a gradual decline of contour detection performance with eccentricity, but for circular contours integration is hardly affected even at highly eccentric locations. This discrepancy in findings could involve many factors such as contour length, shape closure, and unidirectionality of curvature, but in the present study we focus on two factors which we termed predictability and familiarity. Firstly, with circular targets the observer knows beforehand what shape to expect, whereas in snake detection tasks different shapes are typically presented on each trial rendering the precise contour shape unpredictable to the observer. Secondly, the circle is a familiar shape that is immediately apprehended and labeled as a circle. Participants detected snake-like stimuli in central and peripheral vision. We manipulated familiarity by extensively training with one particular snake shape, specific to each observer. We varied predictability by alternating trial blocks with a single shape and blocks with different shapes and found a clear beneficial effect of predictability regardless of eccentricity. Familiarity effects varied between observers, but further research will try to determine whether these effects are partly confounded with characteristics (e.g., complexity, spatial extent) of the specific snake shapes chosen as familiar for the different observers. |
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