ILLUSORY CONTOUR-MOTION ARISING FROM TRANSLATING TERMINATORS

Periodic grating patterns were created by phase shifting or eliminatin g vertical columns of a fine line carrier grating oriented 45 deg. Mot ion was created by translating the patterns parallel to the carrier gr ating. This veridical motion was seen when terminators (i) were create d in low-frequency carriers; (ii) terminated short lines; and (iii) mo ved slowly. In the complementary conditions an illusory contour-motion was seen perpendicular to the orientation of the terminator-defined c ontours, A model involving a competition between second-layer filters (encoding the orientation and motions of the terminator defined contou rs) and double endstopped mechanisms (signalling the presence of termi nators) was developed and found to be in quantitative agreement with t hese data. Experiments with plaids composed of two such patterns were generally consistent with the results of the one-dimensional cases. Co herent ''subjective contour plaid'' motion was almost always seen when the two subjective contours had the same orientation and were perfect ly phase aligned. (C) 1997 Elsevier Science Ltd.