Why are there different types of synesthete?

Abstract

For people with synesthesia, sensations in two modalities are experienced when only one is stimulated (e.g., auditory stimuli might trigger colors and sounds). Synesthetes are manifestly different to the general population, but can also be different to each other. First, the condition is widely heterogeneous in that 60–150 different manifestations of synesthesia have been identified (e.g., auditory stimuli might trigger colors, shapes, flavors and so on; Cytowic and Eagleman, 2009). Second, synesthetes can differ on the quality of their synesthetic perceptions even within a given variant. Some experience their synesthetic percepts as being similar in quality to a real-world perceptions (e.g., synesthetic colors might be projected onto external objects and be difficult to dissociate from real-world colors) while other synesthetes experience less “veridical” percepts (see below). In this opinion piece I ask whether this particular difference—known as the “projector” vs. “associator” distinction—might fall out naturally from another, independent psychological quality.