Abstract
When a moving target is flashed briefly, the position of the flash is mislocalized in the direction of the motion (Cai & Schlag, 2001). A similar forward shift is also reported for the localization of a click added to a moving auditory target (Krüger et al, 2014). However, the reports for touch are mixed: the location of a tactile stimulus presented to a moving finger can be referenced forward in the direction of the finger’s motion (Dassonville, 1994; Watanabe et al, 2009) or backward (Maij et al, 2011). Our goal was to measure this tactile mislocalization and compare it to the auditory case under similar test conditions. We designed a simple tabletop procedure for both, one that could be easily duplicated for classroom use with no equipment. In the touch condition, blindfolded subjects moved their index finger 40 cm across a table leftward or rightward in about 500 ms, either voluntarily or passively. At mid-trajectory, there was a notch in the table that subjects could feel. After completing the hand movement, subjects pointed to the felt location of the notch. Surprisingly, subjects systematically mislocalized the notch backwards, closer to the beginning of their trajectory, when they moved their own hand but not when the experimenter moved it. In the auditory condition, blindfolded subjects passively listened to the sound of a key dragged across the table over the same trajectory, making a click as it passed over the notch. Here, they pointed to a location that placed the click ahead on its path. When subjects had both auditory and tactile information, dragging the key with their own hand, the mislocalizations cancelled. Our simple tabletop tests replicate forward mislocalizations in the auditory domain and suggest that under active control, the felt location of a moving hand lags its physical location.
Meeting abstract presented at VSS 2015