Abstract
Previous studies suggest that line bisection performance shows a leftward bias when completed in peripersonal (near) space and a rightward bias in extrapersonal (far) space, even in an immersive virtual environment (Gamberini, Seraglia, & Prifits, Neuropsychologia, 2007). Furthermore, extrapersonal space can be remapped as peripersonal space by extending reach through tool use; using a stick for bisecting far lines shows the leftward bias whereas using a laser pointer shows the rightward bias. With a head-mounted display showing a computer-simulated environment, participants bisected lines by controlling a free-floating dot, a free-floating hand, or a hand connected by an arm. Lines appeared on a lectern in front of the seated participants while a real lectern provided tactile feedback to match the visual display. Due to large order effects across blocks for mode of bisection (arm/hand/dot), comparisons were made between participants using the first condition encountered. Peripersonal (90cm away) conditions were blocked and counterbalanced as a within-participants factor. At one point in the experiment, between blocks of trials, a virtual needle appeared. Galvanic skin response measured autonomic reaction to watching the needle poke the hand/dot controlled by participants. As a control, half watched the needle poke a second hand/dot. A partial replication of Gamberini et al. (2008) showed a distinction between the arm and dot conditions with the expected leftward and rightward biases, respectively.
Funding for this project was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC).