The time course of the influence of colour terms on visual processing

This thesis explores whether colour terms (e.g., “red”, “blue”, “purple”, etc.) influence visual processing of colour, and if so, the time course of any effect. Broadly, this issue relates to debate concerning whether language affects the way we perceive the world (i.e., the theory of linguistic relativity). Three of the experiments conducted used the event-related potential method (ERP), taking electrophysiological measurements of visual processing and visual cognition in human participants. The ERP provides high-resolution information about the timing of neural activity in the brain and can therefore be used to effectively investigate the time course of a potential influence of colour terms on visual processing. The first study, using a behavioural approach, identified that colour terms can influence the detection of colours and colour-associated objects suppressed from awareness by continuous flash suppression. The second study found that a cross-linguistic difference in colour lexicons affected a post-perceptual ERP component (the P2-N2 complex), but not sensory ERP components occurring early in visual processing. However, the third study found that differences in colour naming within a language do affect an early sensory ERP component (the P1). The final study used ERPs to identify a post-perceptual neural marker (in the posterior P2 component) for the unique ‘pure’ hues (red, yellow, green, and blue), which had previously only been defined and identified linguistically. All of the studies provide evidence that colour terms affect colour processing, and the specific time course of this effect is identified as being task-dependent. These findings have implications for broader debate about the influence of language on visual cognition and perception.