Abstract
It has been conventionally assumed that synesthesia emerges during early childhood, indicating it is an innate trait, as supported by subjective reports. In contrast to this assumption, our investigation, focusing on grapheme-color/sound-color synesthesia, suggests possible acquired synesthesia among players of a Japanese card game. (In this game, players arrange the cards arbitrarily, and every time a reciter reads out a waka-style poem on the card, the players rush to find and touch the corresponding one. The players must memorize the card arrangement and, upon the start of recitation, discern which card is being chosen before they start reaching for the corresponding card.) Our investigation began with a questionnaire survey of experienced players, and the subsequent screening tests narrowed down the identity of synesthetes to 11, as they proclaimed themselves, all of whom were confirmed as synesthetes. The survey was followed by the scrutiny of their synesthesia, investigating whether the distribution of synesthetic colors among the players came in the same way as in a previous study, which indicated that synesthetic colors form clusters in a color space. The analysis of the distribution pattern of synesthetic colors of the 11 subjects revealed that the written/recited words elicit synesthetic colors that form clusters. The results are consistent with those in a prior study, and they also suggest that synesthesia can be acquired even after the onset of the training. Regarding some colors, at least, synesthetic associations are likely to occur, whether congenital or acquired.
