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Contextual effects in speed perception may occur at an early stage of processing.

Record type: Article

How does nearby motion affect the perceived speed of a target region? When a central drifting Gabor patch is surrounded by translating noise, its speed can be misperceived over a fourfold range. Typically, when a surround moves in the same direction, perceived centre speed is reduced; for opposite-direction surrounds it increases. Measuring this illusion for a variety of surround properties reveals that the motion context effects are a saturating function of surround speed (Experiment I) and contrast (Experiment II). Our analyses indicate that the effects are consistent with a subtractive process, rather than with speed being averaged over area. In Experiment III we exploit known properties of the motion system to ask where these surround effects impact. Using 2D plaid stimuli, we find that surround-induced shifts in perceived speed of one plaid component produce substantial shifts in perceived plaid direction. This indicates that surrounds exert their influence early in processing, before pattern motion direction is computed. These findings relate to ongoing investigations of surround suppression for direction discrimination, and are consistent with single-cell findings of direction-tuned suppressive and facilitatory interactions in primary visual cortex (V1)

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Citation

Baker, Daniel H. and Graf, Erich W. (2010) Contextual effects in speed perception may occur at an early stage of processing. Vision Research, 50, (2), pp. 193-201. (doi:10.1016/j.visres.2009.11.011).

More information

Published date: 25 January 2010
Keywords: speed perception, surround suppression, facilitation, plaid

Identifiers

Local EPrints ID: 71958
URI: http://eprints.soton.ac.uk/id/eprint/71958
ISSN: 0042-6989
PURE UUID: 371b6912-53e3-4ed9-bb0d-996abf2b6406
ORCID for Erich W. Graf: ORCID iD orcid.org/0000-0002-3162-4233

Catalogue record

Date deposited: 13 Jan 2010
Last modified: 18 Jul 2017 23:57

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Contributors

Author: Daniel H. Baker
Author: Erich W. Graf ORCID iD

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