Attentional modulation of sensorimotor processes in the absence of perceptual awareness
- *School of Psychology, Cardiff University, Tower Building, Park Place, Cardiff CF10 3AT, United Kingdom; and
- ‡Division of Neuroscience, Faculty of Medicine, Imperial College London, St. Dunstan’s Road, London W6 8RP, United Kingdom
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Edited by Dale Purves, Duke University Medical Center, Durham, NC, and approved May 19, 2006 (received for review March 10, 2006)
Abstract
Attention modulates visual perception and is generally considered inextricably linked with conscious awareness: we become aware of stimuli as we attend to them, and we attend to stimuli as we become aware of them. Recent evidence suggests that attention can also modulate the effects of stimuli that remain invisible, and a natural explanation is that attention enhances weak perceptual representations, bringing them closer to conscious threshold even if they do not reach that threshold. However, there is also the possibility that attention may modulate neural processes that are entirely separate from those supporting conscious perception: sensorimotor mechanisms that do not create awareness however much they are enhanced. Here we provide evidence in support of this second hypothesis by showing that attentional cueing can modulate the behavioral response to invisible stimuli in a way that is distinct from enhancing their visibility. We used a masked-prime paradigm that produces a negative or positive compatibility effect depending on the perceptual strength (duration or brightness) of the prime. We found that attention enhanced the effect of both visible and invisible primes and also increased the likelihood of detecting the prime (i.e., boosted perceptual strength). Crucially, the pattern of attentional influence on priming could not be explained by attentional modulation of the prime’s perceptual strength but was predicted by a direct attentional influence on the nonconscious priming process itself. Therefore, in addition to regulating what we perceive, attention seems to influence our behavior through sensorimotor processes that are not involved in conscious awareness.
Footnotes
- †To whom correspondence should be addressed. E-mail: sumnerp{at}cardiff.ac.uk
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Author contributions: P.S. and P.N. designed research; P.S., P.-C.T., and K.Y. performed research; P.S. and P.-C.T. analyzed data; and P.S. and P.N. wrote the paper.
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Conflict of interest statement: No conflicts declared.
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This paper was submitted directly (Track II) to the PNAS office.
- Abbreviations:
- RT,
- response time;
- cdm−2,
- candelas per square meter.
Abbreviations:
- © 2006 by The National Academy of Sciences of the USA
