Processing Speed in the Motion-Induction Effect

Abstract

Abstract. The motion-induction effect, where an illusory motion is perceived within a bar when it is shown next to a spot presented slightly earlier, was studied with respect to the idea that it is based on differential processing speeds between the two ends of the bar. First, by using just a bar with a luminance gradient, the existence of a motion illusion (gradient motion) within such a bar was demonstrated, presumably due to the different processing speeds of differential luminances. When such a bar was used in the motion-induction effect, it was shown to modulate, for short delays, the strength of the effect up or down, according to the direction of the gradient with respect to the position of the spot. When the same bar was used in the double-motioninduction effect (split priming), in which motion is usually away from the later spot, it totally determined the perceived direction of illusory motion, independently of gradient direction with respect to the later spot or the time between the two spots. These results demonstrate, on the one hand, that differential local processing speed is a likely mechanism to underlie the motioninduction effect. On the other hand, they also suggest the involvement of other more global (and perhaps top -down) processes.

The line motion illusion: The detection of counterchanging edge and surface contrast.

“…In the current study, however, motion was perceived in the opposite direction, toward the light end of the gradient bar when it replaced the uniform bar, perhaps because motion energy is more readily extracted when the gradient bar is exchanged with a uniform bar compared with presenting it on a blank field. When a square was presented, and an adjacent gradient bar appeared afterward, von Grünau et al's (1995) results were very similar to ours. That is, they found that strong LMI motion was perceived when the square was adjacent to the light side of a gradient bar, but not when it was adjacent to its dark side.…”

“…A series of experimental conditions similar to those of the current experiment previously was reported by von Grünau, Saikali, and Faubert (1995). When they presented a gradient bar on a blank field, they found by a relatively small margin that the direction of perceived motion was toward the dark end of the gradient 3 .…”

“…3In a more recent study, Hsieh, Caplovitz, and Tse (2006) did the opposite; i.e., they removed a previously presented gradient bar, leaving only the blank field. Their results differed from von Grünau et al (1995) in two respects: (1) subjects were much more consistent in reporting the direction of the perceived motion, and (2) the perceived motion direction depended on the luminance polarity of the background. Hsieh et al (2006) attributed their results to differences in decay rates within the afterimage of the gradient bar.…”

Endogenous attention and illusory line motion reexamined.

“…This is important, because if (as gradient hypotheses suggest) the modulatory effects of a gradient are strongest at its peaks, then presenting the probe line at a distance from the primers is likely to weaken the ability for gradient-modulated signals at the probe location to influence perception. Several investigations have shown that what appears to be a gradient drops off with distance from the primer in a quasi-exponential fashion (Miyauchi, Hikosaka, & Shimojo, 1992; Steinman, Steinman, & Lehmkuhle, 1995; Stelmach & Herdman, 1991; Stelmach et al, 1994; von Grünau, Racette, & Kwas, 1996; von Grünau, Saikali, & Faubert, 1995). Downing and Treisman's (1997) gaps between the primer and the line probe were 208% the size of their primer.…”

Hemifield asymmetry in the potency of exogenous auditory and visual cues

“…The speed of neural processing is increased by attention, causing sensory data from the line end nearest the cued location to be centrally processed more rapidly (sooner) than data from more remote regions, leading to the percept of sequential line appearance, i.e., motion. That the induced line motion effect is attentional in origin is illustrated by the fact that the illusion can be produced by cue and line stimuli that are perceptually dissimilar in color, luminance and stereo depth (von Grünau, Saikali & Faubert, 1995), and by the ability of both auditory and somatosensory cues to elicit this visual effect (Shimojo, Miyauchi & Hikosaka, 1997). …”