Journal of Vision - Attentional load modulates subconscious orientation processing, by Bahrami, Carmel, Walsh, Rees, & Lavie

Bahador Bahrami	Institute of Cognitive Neuroscience, University College London, Department of Psychology, University College London, and Wellcome Department of Imaging Neuroscience, Institute of Neurology, University College London
David Carmel	Institute of Cognitive Neuroscience, University College London, and Department of Psychology, University College London
Vincent Walsh	Institute of Cognitive Neuroscience, University College London, and Department of Psychology, University College London
Geraint Rees	Institute of Cognitive Neuroscience, University College London, and Wellcome Department of Imaging Neuroscience, Institute of Neurology, University College London
Nilli Lavie	Institute of Cognitive Neuroscience, University College London, and Department of Psychology, University College London

In load theory of attention (Lavie, 1995, 2005), competition between task-relevant and task-irrelevant stimuli for limited-capacity attention does not depend on conscious perception of the irrelevant stimuli. Here we examine whether the level of perceptual load in a relevant task would determine unconscious processing of invisible stimuli. Subjects performed an RSVP task at fixation under conditions of low perceptual load (detecting color targets) or high perceptual load (detecting conjunctions of color and shape). A task-irrelevant tilted grating was also presented monocularly in the periphery, and was suppressed from awareness by continuously flashing a mask stimulus at the same peripheral location in the other eye. Increasing the perceptual load of the fixation task reduced orientation-specific adaptation to the irrelevant and effectively invisible tilted grating. We conclude that even unconcious perception of orientation depends on the availability of spare attentional capacity from a foveal task. These results extend load theory to account for unconscious perception and rule out claims that attentional effects are restricted to conscious representations(Lamme, 2003; Block, 1996).