Tomassini, A;
Solomon, JA;
(2014)
Awareness is the key to attraction: dissociating the tilt illusions via conscious perception.
Journal of Vision
, 14
(15)
10.1167/14.12.15.
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Abstract
The tilt illusion is a compelling example of contextual influence exerted by an oriented surround on a target’s perceived orientation. A vertical target appears to be tilted away from a 15° oriented surround but appears to be tilted towards a 75° tilted surround. We tested the claim that these biases result from distinct sensory processes: a low-level repulsive process and a higher-level attractive process. If this claim were correct, then surround visibility would be a requirement for attraction, but it would not necessarily be a requirement for repulsion. Indeed, Motoyoshi and Hayakawa (2010) have already demonstrated that repulsion can survive removal of the surround from phenomenal awareness using adaptation-induced blindness. Here we sought to test this prediction by measuring the orientation biases in a parafoveally presented Gabor patch surrounded by tilted gratings after 20s adaptation. The adapting stimulus was an annularly windowed plaid composed of a vertical and horizontal jittering gratings. Observers were instructed to maintain fixation throughout the trial and report whether the Gabor appeared to be tilted clockwise or anticlockwise of vertical. They also had to indicate whether the surround was visible after adaptation. Post-adaptation biases were then compared to those obtained in a control experiment without dynamic adaptation. We found large repulsive biases induced by 15° oriented surrounds, but no attractive biases were induced by 75° tilted surrounds. This result shows that attractive effects do require visual awareness, and thereby provides robust evidence for the existence of two separate mechanisms mediating the phenomenology of the tilt illusions.
| Type: | Article |
|---|---|
| Title: | Awareness is the key to attraction: dissociating the tilt illusions via conscious perception |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1167/14.12.15 |
| Publisher version: | http://dx.doi.org/10.1167/14.12.15 |
| Language: | English |
| Additional information: | Copyright © 2014 by Association for Research in Vision and Ophthalmology. Final text available at http://dx.doi.org/10.1167/14.12.15 |
| Keywords: | tilt illusion, visual awareness, adaptation, contextual interactions |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1449206 |
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