Abstract
Visual object displacements are strongly suppressed by visual masking. However, everyday objects often also display haptic displacement cues that are not affected by visual suppression of displacement. Thus, using haptic cues could improve object displacement judgments during periods of low visual sensitivity. However, these cues do not always temporally or spatially overlap with visual cues, which is known to reduce the weighting of information for some tasks. In the current study, we investigated if and under which circumstances visual displacement judgments are affected by haptic displacement cues. We collected psychometric functions of visual displacement judgments during fixation with visual or visuohaptic displacement cues. In both conditions, a peripheral visual target was horizontally displaced by various step sizes following a brief full-screen mask to reduce visual sensitivity comparable to eye movements. The haptic displacement cues were generated by piezo-actuated pins and located under the display directly below the peripheral visual target. Haptic displacement cues were delivered to observers’ right index finger and followed the direction of the visual displacement in half of trials. The haptic cues were temporally, spatially or spatiotemporally aligned with the visual cues. In the spatial alignment condition, haptic displacements were spatially overlapping but preceded visual displacement by 300 ms. In the temporal alignment condition, both displacements occurred concurrently but the visual target was located at a horizontally mirrored location. We found that observers’ point of subjective equality was shifted towards the direction of the haptic displacement suggesting a haptic bias on visual displacement judgments. More importantly, a similar bias was observed when the visual and haptic cues were spatially or temporally misaligned. We suggest that a flexible spatiotemporal window of gathering visual-haptic displacement information can support object tracking during episodes of low visual sensitivity.