Synesthesia: Common Letters And Numbers Are Brighter, Study Suggests

A hallmark of synesthesia is that individuals tend to be idiosyncratic in their experiences, though these experiences are consistent for synesthetes throughout their lifetime.

But new research appearing in the September issue of Psychological Science, a journal of the Association for Psychological Science, adds to a growing body of evidence suggesting that a particular commonality exists across synesthetes, who otherwise have very distinctive experiences.

Psychologist Daniel Smilek and his colleagues at the University of Waterloo have found that a relationship exists between how frequently a synesthete uses a given digit and the brightness of synesthetic color experiences. That is, the more often letters or digits are used in everyday life, the more luminous the synesthetic colors.

Interestingly, the researchers also found that this relationship is not limited to synesthetic color experiences. When non-synesthetes were asked to select a colors to associate with each letter of the alphabet and the digits 0-9, the non-synesthetes also selected more luminous colors for digits and letters used more frequently.

The relationship between letter and digit frequency, and color luminance was much weaker for non-synesthetes than synesthetes, however. Smilek writes "the evidence suggests the possibility that the unusually strong grapheme-color associations made naturally in synesthesia may more closely reflect normal cognitive processes than previously thought."