The effect of two types of induced-motion displays on perceived location of the induced target

Abstract

Using a pointing test, perceived location of a target seen in induced motion was evaluated under two display conditions. In one, a fixated, horizontally stationary spot was surrounded by a frame moving back and forth. As the frame moved to each side, its center shifted correspondingly with respect to the subject's objective median plane. In the second display, the surround was constructed so that as it moved back and forth, its center remained in virtual alignment with the objective median plane. Although both conditions produced a substantial induced-motion effect, only the former produced significant shifts in the target's perceived location. Furthermore, similar shifts were also obtained with a stationary, offcenter frame (Experiment 2). This suggests that the changes in perceived location obtained with the first induced-motion display were not derived from the induced motion per se, but, rather, from a frame effect produced when the surround moved to an off-eenter position. Implications for the relationship between perceived motion and position, as well as for two theories of induced motion, are discussed.

Induced movement in the visual modality: An overview.

“…With an oscillating inducing stimulus, sometimes with tracking eye movements on a moving induced stimulus, the amount of induced movement has not been reported to diminish by having speed of the inducing stimulus well above threshold (Gogel, 1979). It is likely that a moving spot always shows more induced movement than does a fixated spot (Bacon et al, 1982;Bridgeman & Klassen, 1983). Induced movement may never disappear, no matter what the speed of an oscillating inducing stimulus (Becklen & Wallach, 1985).…”

“…For example, in pointing tasks involving judgments of altered displacement, it is implicit that induced movement necessarily affects displacement, which may not be in accord with subjects' perceptions (Bacon et al, 1982;Bridgeman et al, 1981). Tracking induced movement may suppose that a manual task can match perceived velocity of the induced stimulus (Day et al, 1976).…”

“…Mack, Heuer, Fendrich, Vilardi, and Chambers (1985) argued, first, that Roelofs's effect is often found to be incomplete (Bacon et al, 1982;Howard, 1966;Sugarman & Cohen, 1968), whereas movement in an induced movement display may be entirely attributed to the induced stimulus. More crucially, they argued that Roelofs's effect is not truly perceptual but, rather, is judgmental, in a way suggested by Harris might be predicted.…”

“…First, induced movement can occur with an inducing stimulus with no overall direction of motion (Gogel, 1977;Gogel & Griffin, 1982;Nakayama & Tyler, 1978;Relnhardt-Rutland, 1983c;Wade & Swanston, 1984), so that no shift in the observer's straight ahead is possible. Second, Bacon, Gordon, and Schulman (1982) showed that a shift in the perceived straight ahead occurs only if the inducing stimulus undergoes overall displacement. Roelofs's (1935) effect was also reported to probably be weak in a study involving high-speed oscillation of the inducing movement and tracking of a moving induced stimulus (Wallach & Becklen, 1983) and did not correspond to the time course of induced movement in a display filling most of the subject's visual field (Post &Heckman, 1986).…”

“…This can vary in size from a spot often the size of the induced stimulus, itself also a spot (e.g., Carr & Hardy, 1920;Duncker, 1929Duncker, /1938Mack, Fisher, & Fendrich, 1975;Thelin, 1927;Wagenaar et al, 1984), to a pattern filling virtually all the subject's visual field (e.g., Post, 1986;Post & Heckman, 1986). Variations of the frame stimulus involve filling the frame with pattern (e.g., Bacon, Gordon, & Schulman, 1982;Wallach & Becklen, 1983). The shape of the frame is normally rectangular, although circular frames have also been used (e.g., Schulman, 1981;Wallach, 1959).…”