Where I touch is where I see: Visuotactile integration and functional representations of hands and tools.
53.55, Tuesday, May 14, 8:30 am - 12:30 pm, Vista Ballroom
Hayley Colman1, Roger Remington1, Ada Kritikos1; 1School of Psychology, University of Queensland
There is a dissociation in visuotactile integration depending on the effector that we use (either hands or tools) to complete an action (Maravita, Spence, & Driver, 2003; Maravita, Spence, Kennett, & Driver, 2002). This dissociation relies on the binding of visual inputs at the site of action and tactile inputs arising from the hands (Macaluso & Maravita, 2010). During tool use this manifests as an extension of visuotactile peripersonal space and encompasses the tool tip. Here, we investigated how the interactive properties of hands and tools (action affordances) modulate the integration of visual and tactile sensory inputs. We used foot-pedal and saccadic reaction times (SRTs) in a crossmodal congruency task (CCT) to examine this. In Experiment 1, participants made spatial discriminations of visual stimuli arising from either the grasping (palm) or non-grasping (back) regions of the hand or from hand distant space. Visual stimuli were presented concurrently with tactile stimulation on the sides of the index finger of each hand. Participants were faster to detect targets near the hand compared with those distant from the hand and more so when they arose from the palm-adjacent location. This suggests that crossmodal binding is facilitated in the graspable space of the hand. In Experiment 2 participants were trained with straight stick tools. They then completed the CCT whilst holding a re-configured tool that disambiguated the hemi-space of action (end held by the hand) from the hemi-space of effect (tool-tip) by presenting them on different sides of space. In the other hand they held one of the tools used in training. For the re-configured tool, SRTs were faster to the side of space in which the tool-tip was expected given the straight tools used in training. Taken together, these findings indicate that the actions properties of hands and tools modulate visuotactile integration.