Red, green, blue equals 1, 2, 3: Investigating the bidirectionality of digit-colour synaesthesia

In grapheme-colour synaesthesia, letters and digits elicit vivid and highly consistent experiences of colour. Typically, the conscious experience is unidirectional: digits elicit colours but colours do not elicit digits. If synaesthesia reflects an involuntary connection between representations, however, a link between a digit and colour should have some bidirectional effects. Recent evidence shows subtle bidirectional interference effects reflecting this implicit link. Here, we examined whether the implicit activation of a digit by a colour for grapheme-colour synaesthetes could aid their performance, and whether this reflected slow strategic or rapid effortless processing. We presented grapheme-colour synaesthetes with a stream of coloured squares, and asked them to report the colours in order at the end of each trial. Within a trial, all the colours were individually presented for 200ms (fast condition) or 500ms (slow condition). The colours were matched to each synaesthete's colours for the digits one to nine. In half the trials, the order of the colours corresponded to part or all of a sequence of numbers (e.g., red, green, blue if 1=red, 2=green, 3=blue). For the other trials, there was no sequence in the order of colours. If synaesthetes activate, either involuntarily or strategically, the digit that typically elicits the colour when viewing colours, they should be able to use the sequential information to aid the recall of colours in order. Early results suggest that the synaesthetes were able to recall sequential colour sequences more accurately than pseudo-randomized colours. This effect appears greatest for the slow condition, where there is time for strategic transformation, suggesting that synaesthetes are able to use their unusual experiences to effectively cue recall