We examined how Japanese non-synesthetes associate colors to kana characters (Japanese syllabic graphemes). Kana consists of two distinct and corresponding subsets, hiragana and katakana, which represent the same set of syllables but differ in their shapes and usage, etc. For each of 92 kana characters, participants chose the most suitable color from 11 basic color terms. The same test was repeated with a two-week interval. Results showed comparable biases and regularities in their kana-color associations, though, which were not as temporally consistent as those of grapheme-color synesthetes. As suggested for grapheme-color synesthetes in past studies, linguistic and cognitive properties of the characters and colors regulated their associations: earlier characters in the syllabary order tended to be associated with earlier colors in the Berlin and Kay’s typology order, color word frequency order, and/or the subjective color ranking order. Besides, color choices for hiragana characters and those for their katakana counterparts were remarkably consistent, showing that characters sharing the same sound tended to be associated with the same colors. This tendency is comparable with that reported for Japanese synesthetes. It is suggested that grapheme-color associations of both non-synesthetes and synesthetes depend on common linguistic and cognitive processes during language and knowledge acquisition.
