Are color contrast effects present in grapheme-color synesthetes?

Synesthesia is a unique condition in which two sensory modalities are experienced simultaneously. In the case of grapheme-color synesthesia, an individual perceives physically achromatic graphemes (letters and numbers) as a specific color, or "photism". The literature provides conflicting evidence for whether or not these photisms behave similarly to colors in typical vision, but a clear contributing factor remains to be determined. When given optical illusion tasks containing graphemes, synesthetes experience the same perceptions as non-synesthetes would with classic stimuli. By having grapheme-color synesthetes perform a color-contrast task, we can further investigate the connection between synesthetic percepts and typical color vision. It is hypothesized that synesthetic perceptions will not allow synesthetes to see a classic color contrast effect because their photisms will alter the perception of the middle color square of all stimuli equally. Results show that synesthetic percepts are only altering the perception of the stimuli in the achromatic condition. Results indicate that synesthetic