Performance in face perception task is decreased in observers with colour-grapheme synaesthesia

Colour‐Grapheme synaesthesia is one of the more common synaesthesia sub‐types (Colizolo et al, 2012), and it has been investigated in numerous studies exploring different aspects of synaesthesia. Both colour processing and word processing have been extensively studied in non‐synesthetic individuals. The perceptual expertise acquired in letter and word processing has been proposed to be associated with an area of the left occipito‐temporal cortex termed the visual word form area (McCandliss, Cohen, & Dehaene, 2003). Moreover, it has been proposed that neighbouring cortical regions are specialized in processing of colour information (McKeefry & Zeki, 1997). This has led to speculation on whether colour‐grapheme synaesthesia is associated with increased cross wiring between these neighbouring cortical regions (e.g. Ramachandran & Hubbard, 2001). In this study we investigate the impact of increased associations between areas processing colour and visual word forms on a cognitive function, namely face perception, that has bee related to similar brain areas (Kanwisher, McDermott, & Chun, 1997) and thus, may be influenced if colour‐grapheme synaesthets have more elaborate colourgrapheme associations in these areas. Using the Cambridge Face Perception Task (Duchaine, Germine, & Nakayama, 2007) we find that Observers with colour‐grapheme synaesthesia in fact have decreased performance in face perception compared to Observers without synaesthesia. This suggests that an increased association between colours and visual word forms comes at a cost, which seems to affect the ability to process faces.