Abstract
Recent work on synesthesia has begun to emphasize the role of learning in determining the particular inducer concurrent pairings manifested in synesthesia (Rich et al, 2005; Smilek et al, 2007; Eagleman, 2009). Previously we reported on a female color grapheme synesthete with color letter pairings that closely resembled the colors found in a childhood letter set strongly suggesting that an environmental stimulus can shape the development of synesthesia (Witthoft & Winawer, 2006). Here we extend this case study to a group. We present data from an additional 9 synesthetes (4 female / 5 male) with remarkably similar color-letter associations, 8 of who also recall or are still in possession of the same or a similar Fisher Price childhood letter set. All the synesthetes were raised in the US and are in a similar age group (∼27-39 years old). Color matching data and behavioral performance indicative of synesthesia were largely gathered via the synesthete.org website (see Eagleman et al, 2007). Additionally, 5/10 subjects have been tested in the laboratory by ourselves or other researchers (Kim & Blake, 2006; Alvarez & Robertson, 2008). Intersubject correlations for the hues assigned the 24 (I and O are excluded) letters are above 0.99 in some subject pairs, with several subjects choosing almost exactly the same hue for each letter (with all the colors closely matching those in the letter sets). While these data do not comment on the possible importance of genetic factors in determining who will become a synesthete (Ward & Simner, 2002; Barnett et al, 2008; Asher et al, 2009), they do add further support to the idea that, in some people, environmental stimuli can play a strong role in shaping synesthetic associations.