Direct and indirect haptic calibration of visual size judgments in adults and children

Abstract

It has long been suspected that touch plays a fundamental role in the calibration of visual perception, and much recent evidence supports this idea (e.g. Gori et al., 2008; Gori et al., 2010). However, as the range of haptic exploration is limited by the kinematics of the body, the contribution of haptic signals to the calibration process should occur only within the reachable region of the haptic workspace (peripersonal space). To test this hypothesis we measured visual size perception and showed that it is indeed more accurate inside the peripersonal space. We then show that allowing subjects to touch the (unseen) stimulus after observation restores accurate size perception. The accuracy persists for some time, demonstrating that the system has become recalibrated. Finally, we show that observing an actor grasp the object also produces accurate and lasting size perception, suggesting that the calibration can also occur indirectly by observing goal-directed actions, implicating the involvement of the “mirror system”. We are currently measuring calibration of visual bias in children aged 6 to 14 years, and the results will be reported at the conference.