Cross-modal adaptation to self-motion stimuli despite diverted attention

Perception is shaped not only by current sensory inputs, but also by recent stimulus history – a phenomenon known as serial dependence (SD). Perceptual adaptation is a form of repulsive SD, whereby perception shifts away from the previously experienced stimuli. Vestibular and visual self-motion perception exhibit perceptual adaptation, both within and across the two modalities. However, it is unknown whether this requires directed attention to the self-motion stimuli. In this preregistered study, 61 participants experienced a series of vestibular or visual self-motion stimuli. Before each stimulus, the participants were cued to perform either a distractor task (to divert attention away from the self-motion stimulus) or to discriminate their self-motion heading (right or left of straight-ahead). We tested whether several "prior" stimuli with biased headings, but with diverted attention (distractor task), would nonetheless lead to adaptation in heading perception on the following trial. Experiment 1 tested this within each modality separately; Experiment 2 tested cross-modal adaptation. Significant adaptation was seen in both uni-modal conditions (vestibular and visual) and in both cross-modal conditions (visual→vestibular and vestibular→visual). The adaptation magnitude was only modestly, albeit significantly, reduced in comparison to previously published results with attended stimuli. Thus, repulsive adaptation to self-motion stimuli persists without directed attention, even across modalities. The observed cross-modal effects likely point to the inherent linkage between visual and vestibular self-motion processing.