Figure 8.36: Frequency of synesthesia These are the relative frequencies of synesthetic inducers (stimuli that induce synesthesia) and concurrents (the sensory system in which one experiences the synesthesia). As you can see, music and lexical (numbers or letters) stimuli are most apt to induce synesthesia, and the vast majority of the synesthesia effect is in terms of colors (for example, “hearing colors” or seeing specific numbers as specific colors). However, as you can see, many other experiences can induce synesthesia, and they can be expressed in just about all of one’s senses (for example, “tasting numbers” or “smelling sounds.”)

(Adapted from Hochel & Milán, 2008, based on data from Day, 2007.)