title: The effect of response uncertainty on illusory biases of perception and action.
abstract: When task requirements were known in advance, Glazebrook et al. [C.M. Glazebrook, V.P. Dhillon, K.M. Keetch, J. Lyons, E. Amazeen, D.J. Weeks, D. Elliott, Perception-action and the Müller-Lyer illusion: amplitude or endpoint bias?, Exp. Brain Res. 160 (2005) 71-78.] demonstrated that perceptual biases associated with the Müller-Lyer illusion resulted from a misperception of figure extent, while manual aiming biases resulted from a misperception of vertex position. In this study, we examined the degree to which prior knowledge of task requirements influenced how participants coded visual-spatial information associated with Müller-Lyer configurations. Specifically, we investigated how illusory biases are affected when uncertainty exists as to whether participants will be required to make a perceptual-cognitive decision about the length of a figure or complete a rapid aiming movement to a figure vertex. Although aiming movements were completed in a similar manner regardless of the prior knowledge condition, perceptual biases were associated with a misperception of extent when the task was known and a misperception of both extent and position when the task was unknown. These findings indicate that people are flexible in the manner in which they code visual-spatial information.
authors.affiliation: McMaster University, Hamilton, Ont., L8S 4K1 Canada. keetchkm@mcmaster.ca
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Keetch
authors.forename: Cheryl M
authors.initials: CM
authors.lastname: Glazebrook
authors.forename: James
authors.initials: J
authors.lastname: Lyons
authors.forename: Melanie Y
authors.initials: MY
authors.lastname: Lam
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Weeks
authors.forename: Digby
authors.initials: D
authors.lastname: Elliott
mesh_terms: D000328:Adult; D015982:Bias; D003657:Decision Making / Q000502:physiology; D005260:Female; D006801:Humans; D007088:Illusions / Q000502:physiology*; D007600:Judgment / Q000502:physiology; D008297:Male; D009068:Movement / Q000502:physiology*; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*