THE BARBERPLAID ILLUSION - PLAID MOTION IS BIASED BY ELONGATED APERTURES

The perceived direction of motion of plaids windowed by elongated spat ial Gaussians is biased toward the window's long axis. The bias increa ses as the relative angle between the plaid motion and the long axis o f the window increases, peaks at a relative angle of similar to 45 deg , and then decreases. The bias increases as the window is made narrowe r (at fixed height) and decreases as the component spatial frequency i ncreases (at fixed aperture size). We examine several models of human motion processing (cross-correlation, motion-energy, intersection-of-c onstraints, and vector-sum), and show that none of these standard mode ls can predict our data. We conclude that spatial integration of motio n signals plays a crucial role in plaid motion perception and that cur rent models must be explicitly expanded to include such spatial intera ctions.