Synesthesia is not caused by one gene, as long believed, but by many, according to a recent American Journal of Human Genetics study. Researchers linked the neurological condition—characterized by unusual sensory experiences such as seeing colors when hearing sounds [see “Hearing Colors, Tasting Shapes,” by Vilayanur S. Ramachandran and Edward M. Hubbard; Scientific American Mind, Vol. 16, No. 3; 2005]—to regions on four chromosomes. Included in these areas: genes previously implicated in autism, another condition involving excess connections in the brain. That doesn’t mean synesthetes are autistic (or vice versa). But it may explain synesthesialike symptoms reported in some forms of autism. Follow-up studies are under way to see if synesthesia is more common in those with autism and to explore other genetic coincidences, including possible connections among synesthesia, dyslexia and perfect recall (extraordinary memory ability).