title: Up, Down, Near, Far: An Online Vestibular Contribution to Distance Judgement.
abstract: Whether a visual stimulus seems near or far away depends partly on its vertical elevation. Contrasting theories suggest either that perception of distance could vary with elevation, because of memory of previous upwards efforts in climbing to overcome gravity, or because of fear of falling associated with the downwards direction. The vestibular system provides a fundamental signal for the downward direction of gravity, but the relation between this signal and depth perception remains unexplored. Here we report an experiment on vestibular contributions to depth perception, using Virtual Reality. We asked participants to judge the absolute distance of an object presented on a plane at different elevations during brief artificial vestibular inputs. Relative to distance estimates collected with the object at the level of horizon, participants tended to overestimate distances when the object was presented above the level of horizon and the head was tilted upward and underestimate them when the object was presented below the level of horizon. Interestingly, adding artificial vestibular inputs strengthened these distance biases, showing that online multisensory signals, and not only stored information, contribute to such distance illusions. Our results support the gravity theory of depth perception, and show that vestibular signals make an on-line contribution to the perception of effort, and thus of distance.
authors.affiliation: Brain Imaging Centre, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary.
authors.forename: Ágoston
authors.identifier: http://orcid.org/0000-0002-1550-7969
authors.initials: Á
authors.lastname: Török
authors.affiliation: Institute of Cognitive Neuroscience, University College London, London, United Kingdom.|Department of Psychology, Royal Holloway University of London, Egham, United Kingdom.
authors.forename: Elisa Raffaella
authors.initials: ER
authors.lastname: Ferrè
authors.affiliation: Department of Personality, Assessment and Psychological Treatments, University of Barcelona, Barcelona, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Kokkinara
authors.affiliation: Brain Imaging Centre, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary.
authors.forename: Valéria
authors.initials: V
authors.lastname: Csépe
authors.affiliation: Department of Computer Science, University College London, London, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Swapp
authors.affiliation: Institute of Cognitive Neuroscience, University College London, London, United Kingdom.
authors.forename: Patrick
authors.initials: P
authors.lastname: Haggard
mesh_terms: D000328:Adult; D003867:Depth Perception / Q000502:physiology; D004215:Distance Perception / Q000502:physiology*; D005260:Female; D006112:Gravitation; D006257:Head / Q000502:physiology; D006801:Humans; D007088:Illusions; D007600:Judgment; D008297:Male; D009862:Online Systems; D010775:Photic Stimulation; D013028:Space Perception / Q000502:physiology; D014722:Vestibule, Labyrinth / Q000502:physiology*