Synesthetic Color Mapping of Chinese Characters and Kanji: Comparative Analysis among Grapheme-Color Synesthetes in Taiwan and Japan

Grapheme-color synesthetes perceive colors in response to colorless characters, and these synesthetic colors are influenced by specific rule-based linguistic factors. While previous research predominantly focused on the alphabetic writing system, the effects of linguistic factors on synesthetic colors in logographic systems, such as Chinese and Kanji characters, remains unclear. In this study, Taiwanese and Japanese grapheme-color synesthetes were recruited to identify synesthetic colors for 179 shared characters using the Munsell color system. A total of 15,931 character pairs were generated, and relationships based on pronunciation, semantic radicals, and phonetic radicals were examined. Color Similarity Indexes were calculated using negative-transformed z-scores in the CIE Lab* space to quantify color similarity. The linear mixed effect model showed that, for both Taiwanese and Japanese synesthetes, synesthetic colors were more similar when characters shared (1) the same pronunciation, (2) the same semantic radicals, and (3) the same phonetic radicals, compared to when they lacked these shared characteristics. Notably, the regularity effect, wherein phonetic radicals share the same pronunciations as the characters they are embedded in, exerts a more pronounced influence on the synesthetic colors perceived by individuals in Japan as opposed to Taiwan. Our research underscores the intricate link between grapheme-color synesthesia and language processing in Chinese characters/Kanjis, revealing how language use context shapes the perception of both individual elements and their compositions, resulting in the distinctive colors experienced by synesthetes in different countries.