Original photo by xavierarnau/ iStock
Some deaf people have been known to continue signing even after they drift into sleep, through unconscious movements of the hands. The phenomenon is similar to talking in your sleep: The brain’s language and motor circuits remain active while you snooze, though they are suppressed, and during sleep-talking episodes, brain activity more closely resembles the awake state, allowing speech to slip out.
Sign and spoken languages involve similar neural processes, so while hearing people may talk in their sleep, this subconscious impulse takes the form of sleep signing or involuntary hand movements for deaf people. Sleep signing has been documented since as early as 1935, when electrophysiology studies found deaf people made signing motions while asleep. Bursts of activity were observed in the fingers and arms, a pattern not seen in hearing sleepers.
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It's a fibFSL was standardized by French priest Charles-Michel de l’Épée in the 1750s and ultimately influenced ASL, which was standardized throughout the 19th century.
In one widely cited 2017 case, a 71-year-old deaf man with REM sleep behavior disorder was observed signing fluently in his sleep. Because that disorder prevents the usual temporary paralysis that occurs during REM (rapid eye movement) sleep, he was able to sign so clearly that researchers could even decode aspects of his dreams.
This same mind-body link may also explain why dogs sometimes bark or twitch their paws during REM sleep and why some chimpanzees who know sign language have also been observed signing as they snooze.
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Martha’s Vineyard once had its own sign language.
In the 18th and 19th centuries, Martha’s Vineyard, Massachusetts, was home to a surprisingly high number of deaf residents. At its peak, about one in 155 of the island’s residents were born completely deaf, a ratio much higher than in the general U.S. population, in which about one in 5,700 people are deaf. The higher rate in Martha’s Vineyard is believed to have been caused by a hereditary form of deafness traced to settlers from Kent, England.
To communicate, the islanders developed Martha’s Vineyard Sign Language (MVSL), a fully functional language. Many hearing residents also learned and used it daily, making communication seamless across the community. MVSL declined in the late 19th and early 20th centuries when American Sign Language gradually replaced it. It wasn’t rediscovered until the 1970s, when anthropologist Nora Ellen Groce traced the island’s unusually large deaf population and uncovered the language.
Nicole is a writer, thrift store lover, and group-chat meme spammer based in Ontario, Canada.
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