Abstract
Although the aftereffects of prolonged exposure to visual stimuli have been studied extensively, much less attention has been paid to the effects of prior exposure to illusory stimuli on subsequent motor responses. Lyakhovetskii and Karpinskaia (2017) reported that prior exposure to the classical Ponzo illusion (but not the Müller-Lyer) subsequently affected both right-handed pointing accuracy and the speed of hand movement. The present study examined the effects of prior exposure to illusory stimuli on left-handed movements in order to investigate the possibility of hand-dependent effects. Fifty participants took part in the study. We examined two versions of the Müller-Lyer (out-going fins on the upper or lower shafts) and two versions of the Ponzo (classical and inverted). During the exposure phase, illusory stimuli of different sizes were presented ten times to four experimental groups, a different illusion version to each group. In subsequent test trials, neutral stimuli consisting of two equal length lines (without flanks) were presented thirty times. The control group saw the neutral stimuli at all times. After disappearance of each stimulus, participants moved their left-hand across the touch screen to reproduce the lengths of both upper and lower shafts. We recorded the start and the end points of their hand movements (to measure the strength of the effect of prior exposure) and the duration of each hand movement (to calculate the mean speed). The results of our experiment showed that prior exposure to both versions (classical and inverted) of the Ponzo and one version (out-going fins on the upper shaft) of the Müller-Lyer illusions resulted in distortions to the motor responses of subsequently-presented neutral stimuli as well as increases in the speed of movement of the left-hand. Our findings demonstrate that the effects of exposure to illusory stimuli in the sensorimotor domain are hand dependent.
Meeting abstract presented at VSS 2018