Some people see numbers as always having certain colors — for example, they see the number 5 as red. A new study reveals that their eyes react as if they see those colors in the real world.
The study found that people with synesthesia — a neurological condition in which the senses blend together — don't just experience these colors in their minds. Instead, they show real, measurable differences in their pupils, as if they were seeing the colors in real life. The findings, posted March 6 in the journal eLife, suggest that in people with synesthesia, the brain processes internally generated colors and real visual input in a similar way, the study authors say.
