Is non-synesthetes’ B Blue? Grapheme–color association improves non-synesthetes’ detection in visual search

Grapheme–color synesthesia is expected to provide a clue to solving the “binding problem” of visual features. Synesthetic research uses non-synesthetes as a control group and shows that synesthetes perform better with synesthetic color congruency, while non-synesthetes’ performances do not. However, non-synesthetes also have certain grapheme–color associations. Therefore, this study examined whether non-synesthetes’ grapheme–color associations improve their performance in a visual search task. The results indicated that non-synesthetes were significantly faster at detecting congruent targets with their grapheme–color associations, such as red for “A,” blue for “B,” and yellow for “C.” However, the effect was not found in relation to numerical characters. This study has implications for future neuroscience and consciousness research regarding grapheme–color synesthesia.