Tactile inputs resolve the ambiguous perception of biological point light walkers
23.427, Saturday, May 11, 8:30 am - 12:30 pm, Orchid Ballroom
Yiltiz Hormatzhan1, Lihan Chen1,2; 1Center for Brain and Cognitive Sciences and Department of Psychology, Peking University, 2Key Laboratory of Machine Perception (Ministry of Education), Peking University
Point light walker (PLW) has been widely applied to address the biological motion processing in the visual modality. Biological PLW has been recently employed in multisensory research, in which task-irrelevant auditory cues would bias the perception of walking direction of ambiguous PLWs (Brooks et al., 2007). In current study we asked whether the tactile inputs, which simulate the hitting grounds by foots, could affect the ambiguous directional perception of PLWs. We presented binocular rivalry PLWs with 13 red and 13 cyan dots, the two PLWs could be either upright or either inverted. One tap was always synchronized with the hitting of the visual foot of one PLW, and the other tap could lead (150 ms), synchronize or lag (150 ms) the other hitting foot of this PLW. Participants wore glasses with a red filter on the left eye and a cyan filter on the right eye during the course of the experiments and performed two tasks: (1) Motion Direction Determination ("Motion" task)-they were asked to press and hold the left or right foot switch which corresponds to the dominant perception of "left" or "right" direction of the PLWs ; (2) Visual Dots Number Comparison ("Number" task), in which the participants were required to discriminate whether red dots were more than cyan dots or vice versa. The results showed the synchronous inputs of tactile taps increased the delectability of motion directional discrimination in "upright" condition but it was not the case in the "invert" condition. Interestingly, for the "Number" task, the PLW synchronized with the tactile inputs were perceived to be more in dots. These findings suggest that tactile inputs, which consist of apparent motion, affect the visual apparent motion of PLW, this effect could not be reduced to a general shift in visuo-spatial attention, as reflected in the Number task.