Synesthesia —from the Ancient Greek σύν (syn), “together,” and αἴσθησις (aisthēsis), “sensation“—is a neurologically-based condition in which stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway.
Common forms of synesthesia:
– grapheme – letters or numbers are perceived as inherently colored
– number form synesthesia
– sound synesthesia – hearing sounds in response to visual motion and flicker