Visual and Vestibular Perceptual Thresholds Each Demonstrate Better Precision at Specific 1 Frequencies and Also Exhibit Optimal Integration 2 3 Running Title: Visual & Vestibular Perceptual Threshold Dynamics 4 5

42 Prior studies show that visual motion perception is more precise than vestibular motion 43 perception, but it is unclear whether this is universal or the result of specific experimental conditions. 44 We compared visual and vestibular motion precision over a broad range of temporal frequencies by 45 measuring thresholds for vestibular (subject motion in the dark), visual (visual scene motion) or visual46 vestibular (subject motion in the light) stimuli. Specifically, thresholds were measured for motion 47 frequencies spanning a two-decade physiologic range (0.05 Hz to 5 Hz) using single-cycle sinusoidal 48 acceleration roll tilt trajectories (i.e. distinguishing left-side down from right-side down). We found that 49 while visual and vestibular thresholds were broadly similar between 0.05 and 5.0 Hz, each cue is 50 significantly more precise than the other at certain frequencies. Specifically, we found that: 1) visual 51 and vestibular thresholds were indistinguishable at 0.05 Hz and 2 Hz (i.e. similarly precise), 2) visual 52 thresholds were lower (i.e. vision more precise) than vestibular thresholds between 0.1 Hz and 1 Hz, 53 and 3) visual thresholds were higher (i.e. vision less precise) than vestibular thresholds above 2 Hz. 54 This shows that vestibular perception can be more precise than visual perception at physiologically 55 relevant frequencies. We also found that sensory integration of visual and vestibular information is 56 consistent with static Bayesian optimal integration of visual-vestibular cues. In contrast with most prior 57 work that degraded or altered sensory cues, we demonstrated static optimal integration using natural 58 cues. 59 Introduction 60 We perceive self-motion with exquisite precision. Prior studies show that visual perception is 61 more precise than vestibular perception when discriminating linear motion (Gu et al. 2008; Fetsch et 62 al. 2009; Butler et al. 2010; MacNeilage et al. 2010; Fetsch et al. 2012). However, it is unclear 63 whether visual precision is universally better than vestibular precision or if these findings are the result 64