Cue Combination in Visual and Vestibular Perception of Subjective Vertical

Poster Presentation 43.470: Monday, May 22, 2023, 8:30 am – 12:30 pm, Pavilion
Session: Multisensory Processing: Audio-visual, visuo-vestibular

Chela Willey1 (), Zili Liu2; 1Loyola Marymount University, 2University of California, Los Angeles

Subjective vertical is the perceptual estimate of the direction of gravity in an environment. Several sensory modalities, including vestibular and visual systems, produce seemingly independent estimates of vertical. These individual sensory estimates are thought to combine to produce the end perception of subjective vertical. In the current study, we isolated sensory estimates of subjective vertical in two conditions in which participants discriminated subjective vertical while in the presence of either only visual or only vestibular cues. Using the method of constant stimuli, we fitted participant’s data in each condition with a psychometric function and calculated bias and sensitivity. From these isolated sensory conditions, we calculated the psychometric parameters of the optimal observer using standard Gaussian distributions with the assumption that the two cue conditions were independent. We compared bias and sensitivity of the optimal observer with participant’s empirical data obtained in a combined sensory condition with full vestibular and visual cues present. We found that participants were sub-optimal in how they weighed sensory cues. Biases in the combined cue condition did not differ significantly from predicted optimal observer biases. However, the optimal observer predicted greater sensitivity than what was found in participants’ data in the combined cue condition. Overall, participants heavily relied on visual cues in the combined condition, despite greater reliability of vestibular cues.