Abstract
When J an alphanumeric-color synaesthete views black digits or letters, each grapheme is perceived as having a colored overlay or photism. For J these photisms are projected in space, sitting atop the digit or letter, but conforming to the shape of the grapheme. Previous experiments using Stroop methods showed that viewing black graphemes automatically induces photisms (e.g., viewing a 5 automatically induces a pink photism; viewing an S induces a green photism) Here we used Stroop methods to show that viewing ambiguous graphemes (e.g., a “scoreboard” 5 that can be interpreted as a 5 or an S) automatically induces different colored photisms depending on whether the graphemes are interpreted as digits or letters. Ambiguous graphemes such as a scoreboard 5 were embedded in digit strings (e.g., 3 4 5 6 7) or words (e.g., MUSIC). Each ambiguous grapheme then appeared alone in a video color that J had to name. In the digit context, ambiguous graphemes appeared in colors that were congruent or incongruent with J's photisms for the digit interpretation of the grapheme. In the letter context, colors were congruent or incongruent with J's photisms for the grapheme's letter interpretation. Crucially, what was a congruent trial in one context was always an incongruent trial in the other context (e.g., a pink scoreboard 5 was congruent if a digit, but incongruent if a letter; a green scoreboard 5 was incongruent if a digit, but congruent if a letter). In both the digit and letter contexts, colors in the congruent condition were named significantly faster than colors in the incongruent condition. Because the colored graphemes in the digit and letter contexts were identical, we conclude that the same ambiguous graphemes induced different colored photisms depending on whether they were interpreted as digits or letters. This finding supports a model of alphanumeric synaesthesia in which graphemic form activates meaning and meaning activates color along reentrant pathways.
This research was supported by the Natural Sciennces and Engineering Research Council of Canada.