Abstract
[Purpose] We investigated attentional facilitation around the observer's hand, which was hidden from the eye, using flash lag effect (FLE). The FLE is known to be reduced by attention and can be used as the index of attention. [Method] We compared the FLE of the stimulus presented either in the left or right of the fixation with various hand conditions: either left or right hand was positioned at left or right stimulus location. Visual stimulus was seen through a mirror, which covered the observer's hand, and the position of the invisible hand was arranged to be right above the stimulus. White disk with a red bar rotating on it was presented at each stimulus location. A red dot was presented near each end of the rotating bar on either of the disks at unpredictable timing. The observer was instructed to memorize the relative location of the dots and rotating bar. The relative location was reproduced after the trial and recoded as the FLE. There were two attentional conditions. In one condition, the disk with flash was informed before each trial (Single condition) and it was not in the other condition (Double condition). We also measured EEG, and analyzed SSVEP to the disks and ERP to the flash presentations. [Results] The flash presented near the hand resulted larger FLE, comparing with the flash far from the hand. Hand effect was similar for the Single and Double conditions while the FLE was smaller in the Single condition due to the endogenous attention. That is, the attentional effect was increased near the hand even at the location where the observer asked to attend. This attentional effect near the hand was supported by both SSVEP and ERP responses. We conclude that there is attention around the hand, which is attracted automatically by hand.
Meeting abstract presented at VSS 2016