Visuotactile object processing in binocular rivalry: The role of shape congruence, voluntary action, and spatial colocalization

Multisensory information can help resolve perceptual ambiguity in situations such as the alternating visual experience during binocular rivalry. Across four experiments, participants viewed dichoptically presented spiky and round rival targets while simultaneously touching spiky, neutral, or round shapes in three-dimensional (3D) printed form. The primary aim was to investigate the influence of visuotactile shape congruence in the curvature dimension. In addition, the roles of voluntary action and spatial colocalization on successful crossmodal integration were investigated. Voluntary action was tested between active touch (Experiments 1 and 2) and passive touch (Experiments 3 and 4) conditions. Visual stimulus type differed between rapid successions of 3D-rendered images (Experiments 1 and 3) and real-world video recordings (Experiments 2 and 4), with the latter involving bodily cues to promote visuotactile colocalization. In general, the results showed that tactile shape congruence can lead to relative dominance of the corresponding visual target, especially when visuotactile colocalization was encouraged with video recordings as visual targets. The results suggest beneficial effects of crossmodal shape congruence on disambiguation, which seems to be generally comparable between the two modes of active versus passive touch. Using 3D stimuli and including free voluntary action, the study provides novel and connecting insights into the naturalistic object processing behavior of humans.