Synesthesia — the mysterious phenomenon of "mixed senses" — is thought to affect a small fraction of the general population. But among people with autism spectrum disorders, the condition might be significantly more common, fascinating new research suggests.
In a study published this week in Molecular Autism, a team out of Cambridge University set out to test what had been anecdotally reported for some time: that individuals with Asperger's syndrome often exhibited signs of synesthesia, such as "tasting" words or "seeing" music in the form of colors. They recruited 164 adult participants with autism and 97 participants without the condition, and relied on self-reporting to screen all of them for synesthesia. Of that study population, around 19 percent of adults with an autism spectrum disorder also experienced synesthesia, compared to 7.2 percent of those in the control group.
Hearing a sound triggers the perception of a specific color
The most common forms of synesthesia reported by study participants with autism were "grapheme-color," or the perception that letters or numbers are colored, and "sound-color," wherein hearing a sound triggers the perception of a specific color.
Of course, this research is preliminary, and it's also hampered by a reliance on self-reporting. Subsequent research, investigators hope, might use brain imagery to further validate the connection between autism spectrum conditions and an increased likelihood of synesthesia. And already, researchers have some ideas of why that link might exist: both autism and synesthesia are thought to involve unconventional neural development and have genetic underpinnings. Unraveling those overlaps might, one day, cultivate an enhanced understanding of the biological mechanisms behind the conditions.
"This research gives us an exciting new lead," said study co-author Simon Fisher in a statement, "encouraging us to search for genes which are shared between these two conditions, and which might play a role in how the brain forms or loses neural connections."