New insights into mechanisms of enhanced synaesthetic memory: Benefits are synaesthesia-type-specific.

The goal of this study was to test the nature of the memory advantage in synaesthesia. We compared four different types of synaesthetes (27 grapheme-colour, 21 sound-colour-, 25 grapheme-colour-and-sound-colour- and 24 sequence-space synaesthetes) to their matched controls. Recognition memory for three types of stimuli (music, words, colour) was tested. We anticipated a general advantage in memory for synaesthetes and potentially additional synaesthesia-specific benefits. The results showed a general advantage for synaesthesia. Further, a benefit for colour stimuli resulted for grapheme-colour synaesthetes and a benefit for music stimuli resulted for grapheme-colour-and-sound-colour synaesthetes, indicating synaesthesia-type specific effects. These results suggest different mechanisms for the explanation of the memory benefit for different types of synaesthesia such as synaesthesia-related colour expertise for grapheme-colour synaesthesia and additional encoding opportunities for grapheme-colour-and-sound-colour synaesthesia.