Exploring the functional nature of synaesthetic colour: Dissociations from colour perception and imagery.
Rocco Chiou, Anina N Rich, Sebastian Rogers, Joel Pearson
Cognition August 2018 DOI: 10.1016/j.cognition.2018.03.022 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Experimental psychophysics study Peer reviewed |
|---|---|
| Population | Individuals with grapheme-colour synaesthesia and non-synaesthetes |
| Keywords | Attention Binocular rivalry Colour Consciousness Priming Synaesthesia |
| Key findings | Synaesthetic colour induced a facilitatory priming bias on binocular rivalry that was not constrained to the inducing grapheme's location, unlike the location-dependent suppressive bias produced by normal colour perception. This priming was absent in non-synaesthetes, was not due to response bias, depended on visual attention, and resisted sensory perturbation. Colour imagery in synaesthetes produced global priming, whereas imagery in non-synaesthetes produced local priming. |
Abstract
Individuals with grapheme-colour synaesthesia experience anomalous colours when reading achromatic text. These unusual experiences have been said to resemble 'normal' colour perception or colour imagery, but studying the nature of synaesthesia remains difficult. In the present study, we report novel evidence that synaesthetic colour impacts conscious vision in a way that is different from both colour perception and imagery. Presenting 'normal' colour prior to binocular rivalry induces a location-dependent suppressive bias reflecting local habituation. By contrast, a grapheme that evokes synaesthetic colour induces a facilitatory bias reflecting priming that is not constrained to the inducing grapheme's location. This priming does not occur in non-synaesthetes and does not result from response bias. It is sensitive to diversion of visual attention away from the grapheme, but resistant to sensory perturbation, reflecting a reliance on cognitive rather than sensory mechanisms. Whereas colour imagery in non-synaesthetes causes local priming that relies on the locus of imagined colour, imagery in synaesthetes caused global priming not dependent on the locus of imagery. These data suggest a unique psychophysical profile of high-level colour processing in synaesthetes. Our novel findings and method will be critical to testing theories of synaesthesia and visual awareness.