Kennedy, J.M & Wnuczko, M.J. University of Toronto at Scarborough

POINTING TO NEARBY TARGETS IS (1) LOWER WITH A TACTILE VANTAGE POINT THAN WITH VISION, AND (2) UNDERESTIMATES FORESHORTENING

Two-Fulcrum Theory of pointing contends that in pointing with vision, the eyes are the fulcrum, and the pointing finger approaches the line of sight, without occluding the target, but in pointing without vision, the shoulder is the fulcrum. To test this theory, participants pointed to a set of objects stretching into the distance. Pointing with eyes closed was followed by pointing with eyes open. In both cases, we measured the elevation of the pointing arm. How should the elevation change as the targets become more distant? ART theory (Juricevic & Kennedy, 2006) argues the rate of foreshortening of distant spaces should be underestimated. In our experiment on pointing, eight targets were used. The distances between adjacent pairs of targets were constant. Therefore angles subtended by adjacent pairs of targets foreshortened i.e. shrank with distance. As predicted, the arm was elevated more in pointing with vision than in pointing blindfolded, and the increase in arm elevation as targets became more distant underestimated foreshortening.

Experiment March 18th 2008 -- > Pdf File [256 kb]