Like everyone else, deaf individuals are capable of communicating both outwardly and internally in a number of different ways – therefore there is no single language or modality that all deaf people use when thinking. The nature of a person’s thoughts is likely to be influenced by various factors, including the age at which they became deaf and other personal factors such as whether or not they have an internal monologue.
Though there’s little published research on this topic, sign language linguist Professor Bencie Woll of University College London did explain in a recent interview with The Naked Scientists that “a person who was born deaf, the languages they might think in are going to be related to the languages they know. You can see young deaf children signing to themselves just the way young hearing children speak to themselves.”
Some profoundly deaf people – meaning those who have little to no hearing – may think in images rather than sounds, and picture their thoughts in the form of sign language signs, written words, or pictures. That’s not to say their internal world is any less rich or descriptive than that of people who aren’t deaf, it just comes across via a different medium.
And while those who are born deaf are unlikely to have an internal reference for what spoken language sounds like, others become deaf later in life and therefore retain the memory of verbal communication. As a result, some deaf people may think in images, in sound, or a mixture of the two.
It’s also worth noting that sign language isn’t universal – there are around 300 different sign languages in use around the world. The type of sign language that a deaf person pictures in their head when thinking will therefore depend on the dialect that they use.
Fascinatingly, studies have shown that thinking in sign language activates the brain’s left inferior frontal cortex, which is the same region engaged when individuals who aren’t deaf think to themselves in words. “This suggests that ‘inner signing’ is mediated by similar regions to inner speech,” write the authors of one 1997 study on this subject.
Other research conducted way back in the 1970s has indicated that inner signing plays a central role in short-term memory processes, just as inner speech is known to do in individuals who aren’t deaf.
Yet that’s not to say that all people who aren’t deaf think verbally. Over the past few years, it’s become more widely known that some people have no internal monologue, meaning their thoughts are silent and consist only of images or other abstract constructs that don’t involve speech.
It’s unclear how common this phenomenon is in deaf people or whether they experience it at the same rate as the non-deaf population.
Some people also have aphantasia, which means they are unable to conjure up any mental imagery. So far, there doesn’t appear to have been any research done to assess aphantasia among deaf people, so it’s unclear how individuals with no audible or visual thoughts might think.
