Blue bananas and colorful letters: how synesthetic experiences affect perception of gray stimuli

Hansen and colleagues (2006) presented participants with objects of stereotypical colors (e.g., banana) and asked them to adjust the color of the object, so that it appeared gray on the screen. They found that participants over-adjusted the color to slightly blue, as a perfect gray banana was judged as still holding residuals of yellow. The color knowledge of familiar objects influenced color perception, creating a “memory color” effect. In grapheme-color synesthesia, individuals experience color photisms whenever they perceive black graphemes. The present study tests whether synesthesia inducers can also produce a memory color effect. Synesthetes and non-synesthetes will perform the task designed by Hansen et al. (2006), adjusting to gray a set of objects of stereotypical colors and color neutral objects. A set of graphemes will be added to the stimuli list. A memory color effect is expected in both the stereotypical object and grapheme conditions for synesthetes, but only in the former condition for non-synesthetes. Furthermore, we will explore whether the strength of the memory color effect correlates with the participants’ mental imagery skills and the synesthetes’ ability to consistently report their synesthetic colors overtly. The results could help designing an indirect method to measure synesthetic perceptual experiences.