title: A Bayesian model of perceived head-centered velocity during smooth pursuit eye movement.
abstract: During smooth pursuit eye movement, observers often misperceive velocity. Pursued stimuli appear slower (Aubert-Fleishl phenomenon [1, 2]), stationary objects appear to move (Filehne illusion [3]), the perceived direction of moving objects is distorted (trajectory misperception [4]), and self-motion veers away from its true path (e.g., the slalom illusion [5]). Each illusion demonstrates that eye speed is underestimated with respect to image speed, a finding that has been taken as evidence of early sensory signals that differ in accuracy [4, 6-11]. Here we present an alternative Bayesian account, based on the idea that perceptual estimates are increasingly influenced by prior expectations as signals become more uncertain [12-15]. We show that the speeds of pursued stimuli are more difficult to discriminate than fixated stimuli. Observers are therefore less certain about motion signals encoding the speed of pursued stimuli, a finding we use to quantify the Aubert-Fleischl phenomenon based on the assumption that the prior for motion is centered on zero [16-20]. In doing so, we reveal an important property currently overlooked by Bayesian models of motion perception. Two Bayes estimates are needed at a relatively early stage in processing, one for pursued targets and one for image motion.
authors.affiliation: School of Psychology, Cardiff University, Park Place, Cardiff CF10 3AT, UK. freemant@cardiff.ac.uk
authors.forename: Tom C A
authors.initials: TC
authors.lastname: Freeman
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Champion
authors.forename: Paul A
authors.initials: PA
authors.lastname: Warren
mesh_terms: D001499:Bayes Theorem; D006257:Head; D006801:Humans; D007088:Illusions; D008954:Models, Biological; D009039:Motion Perception / Q000502:physiology; D009068:Movement / Q000502:physiology*; D011698:Pursuit, Smooth / Q000502:physiology*
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