Idiosyncratic selection of active touch for shape perception

Abstract

Hand movements are essential for tactile perception of objects. However, the specific functions served by active touch strategies, and their dependence on physiological parameters, are unclear and understudied. Focusing on planar shape perception, we tracked at high resolution the hands of 11 participants during shape recognition task. Two dominant hand movement strategies were identified: contour following and scanning. Contour following movements were either tangential to the contour or oscillating perpendicular to it. Scanning movements crossed between distant parts of the shapes’ contour. Both strategies exhibited non-uniform coverage of the shapes’ contours. Idiosyncratic movement patterns were specific to the sensed object. In a second experiment, we have measured the participants’ spatial and temporal tactile thresholds. Significant portions of the variations in hand speed and in oscillation patterns could be explained by the idiosyncratic thresholds. Using data-driven simulations, we show how specific strategy choices may affect receptors activation. These results suggest that motion strategies of active touch adapt to both the sensed object and to the perceiver’s physiological parameters.

Predictive Eye Movements Characterize Active, Not Passive, Participation in the Collective Embodied Learning of a Scientific Concept

“…In order to measure the inter-observer reliability, we measured the intra-class correlation (ICC) of the two measurements, and received r_ICC = 0.68 for the active subjects, r_ICC = 0.58 for the passive, and r_ICC = 0.95 for the combined data set (active and passive together). The inter-observer reliability values fell within the range of the inter-observer reliabilities previously found in our lab [66] and elsewhere [67]. The high level of inter-observer correlation for the combined data set reflects the fact that the noise coming from the difference between the observers was small compared to the signal we reported.…”