VISUAL-PERCEPTION OF CHANGING SIZE - EFFECT OF OBJECT SIZE

Since marked threshold elevations specific to changing size were produced by rectangular stimuli whose widths were less than 1.5°, but not by wider rectangles we suggest that changing size filters are not sensitive to pairs of edges separated by more than about 1.5°. We measured the spatial spread of adaptation to oscillating size and to oscillating position. Threshold elevations fell off exponentially as the test rectangle was made progressively wider than the adapting rectangle. Threshold elevations fell off exponentially, but less rapidly, when the rest rectangle was made progressively narrower than the adapting rectangle. These findings can be explained if there is lateral inhibition between neighbouring motion filters that are sensitive to oppositely-directed motion. We report evidence that adaptation of these changing-size filters contributes to the changing size aftereffect. On this basis we suggest that the activity of changing-size filters is involved in the perception of changing size at superthreshold as well as at threshold levels of sensation. © 1979.