Abstract
The determinants of synesthetic color choice for Japanese characters were studied in six Japanese synesthetes, who report seeing color for characters, numerals and letters. Four possible determinants were investigated: visual form (script), character frequency, sound, and meaning. Three kinds of Japanese characters were used as stimuli: Hiragana, Katakana, and Kanji. Hiragana and Katakana are both Japanese phonetic characters that represent the same set of syllables although their visual forms are dissimilar. Hiragana characters appear much more frequently in Japanese texts than do Katakana characters. Kanji characters are logographs, which represent a meaning or a concept, like a content word does. There are many homophones among Kanji characters. Also many Kanji characters share the same visual components (radicals) although their sounds and meanings are dissimilar. By using Hiragana, Katakana, and Kanji characters, we could dissociate effects of sound, visual form, character frequency, and meaning in Japanese grapheme-color synesthesia. From a palette of 138 colors, the synesthetes selected a color corresponding to each character. The experimental sessions were repeated three times to assess participants' consistency of color choices. The results for Hiragana and Katakana characters were remarkably consistent. This indicates that color selection depended on character sounds, not on visual form or character frequency. The color selections for Kanji numerals were remarkably consistent with those for Arabic numerals, which had been tested separately. Furthermore, Kanji characters which represent color names and names of objects with high color diagnosticity were represented by the corresponding colors, indicating that meaning was a strong determinant of synesthetic color choice for Kanji characters. These results suggest that sound and higher order processing (i.e., semantics) are involved in Japanese grapheme–color synesthesia.