Context and the motion aftereffect: occlusion cues in the test pattern alter perceived direction

A horizontally moving vertical grating viewed through a diamond-shaped aperture can be made to appear to move either upwards or downwards by introduction of appropriate depth-ordering cues at the boundaries of the aperture (Duncan et al. 2000 Journal of Neuroscience 20 5885-5897). The grating is perceived to move towards (and sliding under) occluding 'near' surfaces, and parallel to 'far' surfaces. Here we show that these depth-ordering cues affect the perceptual interpretation of the motion aftereffect (MAE) as well. After adaptation to unambiguous horizontal motion, the MAE direction deviates from horizontal towards near surfaces. However, the influence of depth-ordering cues on the illusory motion of the MAE is generally less than that seen for 'real' motion. Implications for theories of depth-motion and depth-MAE interactions are discussed.