Seeing Color? Where? Current Standing in Projector and Associator Grapheme-Color Synesthesia Research.

Abstract

Synesthesia is a neurological condition where a perceptual experience of a stimulus triggers a new perceptual experience, which is not caused in non-synesthetes. For instance, in grapheme-color synesthesia, a black grapheme “a” can induce the perception that the grapheme is colored “red”. It has been a matter of controversy whether the synesthetic percept arises due to bottom up processing of the initial stimulus or if the stimulus needs to be fully processed and subsequently induces the synesthetic percept by top down processing, due to evidence apparently supporting both views. To explain these diverging findings, a distinction was made between “projector” and “associator” synesthetes by Dixon, Smilek, & Merikle (2004). The former perceive the induced color in the outside world, on top of the grapheme, while the latter perceive the color in their minds eye. This articles reviews research which has addressed whether projectors and associators differ in neurobiology and/or cognition as well as how differing methods of differentiation between projectors and associators influence results. Results indicate that there are indeed cognitive and neurobiological differences between projector and associator grapheme-color synesthetes and that the method used to distinguish between the two may influence the results of the experiments. Suggestions for increasing reliability and accuracy of projector/associator differentiation for future research are also discussed.