Talking to yourself in your head is a normal part of being human. It plays an important role in our working memory (“don’t forget the milk”), planning (“I’ll go to the store after lunch and pick up the milk”) and reflection (“crap, I forgot the milk”), as well as in reasoning and self-motivation.
Not everybody experiences inner speech in the same way. Some people’s inner speech would translate well into a book, while others use a more abstract and condensed form of language. Some people frequently stage conversations in their heads, sometimes so vividly that they wonder whether the conversations actually occurred (“I’m sure I told you this already”).
Surprisingly, inner speech isn’t a universal experience. How often people experience inner speech varies from constantly to almost never—a completely unfathomable idea to somebody whose brain never shuts up.
There’s also evidence that young children may not experience inner speech, or at least inner speech like we experience it. When given a set of pictures to learn, children over the age of seven find it harder to recall phonologically similar (words that sound similar) items than dissimilar ones.
This suggests that they’re converting images to words in their heads, and the words’ similarity is causing confusion. In children under seven, however, this effect isn’t observed, implying that they’re not using verbal rehearsal, or inner speech, in the task.
We all have imaginary friends
Although sometimes portrayed as sinister in scary movies, it’s quite normal for young children to talk out loud to themselves. Children between three and eight generally transition from talking out loud to whispering and semi-internalizing their speech until the behavior eventually fades.
While the speech is audible, it isn’t intended for an audience and often includes instructions on how to complete a task or how to behave, like, “I’m not going to put Mom’s lipstick in my mouth today.” It’s possible that this kind of speech, known as private speech, is the developmental precursor to inner speech.
Even children’s imaginary friends may not be so different to our own internalized imaginary conversations. As children “hear” their friend talking to them and then socially respond, there’s the interesting possibility that having imaginary friends helps children develop internal speech (in addition to freaking out their parents).
The developmental progression away from private speech raises the question of whether inner speech is simply a quiet, internalized version of talking or if it’s a totally different neural process.
Is inner speech just quiet talking?
Neuro-imaging techniques have revealed areas of the brain that are active during both inner and overt speech.
This overlap in brain activity, like in Broca’s area or the left inferior frontal gyrus (or more specifically, in the ventral portion of the pars opercularis), supports a link between the processes of verbal speech and inner speech.
Additionally, disrupting the posterior superior temporal gyrus using magnetic pulses into the brain (a kind of frightening-sounding technique called repetitive transcranial magnetic stimulation) hindered both verbal working memory and speech production, again suggesting at least some overlap between the brain processes.
Subvocalization – Really quiet talking isn’t as silent as you think
Every time you use your inner voice, the muscles that work with your actual voice are still doing their thing. You might not be able to hear it, but electromyographs can by measuring the electrical nerve signals of your throat muscles firing.
A NASA team conducted extensive research in the subvocalization field before losing funding. That doesn’t make it any less crazy, as the technology was reportedly able to recognize up to 2000 different words. It did, however, rely on some cumbersome electrodes hanging off different areas of the face and throat, giving Google Glass a run for its money in the fashion industry.
Is your inner voice cramping your speed reading style?
Subvocalization is also at the center of the speed reading debate. Some speed reading gurus argue that it places limits on fast we can read ( if you’re saying every word as your reading, wouldn’t that mean you could only read as fast as you talk? ).
Others say that to comprehend what you’re reading, using your inner voice necessary. Not only that, but using sensors like Chuck Jorgensen’s, researchers found that even the fastest readers all subvocalize even if they thought they didn’t.
We all hear voices. We just know they’re our own
Understanding the brain’s processing of inner speech is important, as abnormalities may help explain the psychological phenomenon of hearing voices.
Experiencing auditory visual hallucinations (AVH) is common in disorders like schizophrenia, a condition that affects 1.1% of the US population and bears no resemblance to Jim Carrey in “Me, Myself and Irene.”
Hearing voices that aren’t there may be a consequence of the brain mistakenly interpreting inner speech as coming from an outside source. A 2012 Finnish neuroimaging study by Tuukka Raik and Tapani Riekki scanned the brains of people experiencing auditory hallucinations and then compared their brain activity to when the participants were imagining the hallucinations.
During both processes, the fronto-temporal language-related areas of the brain were activated, suggesting that hallucinations are similar to inner speech.
The supplementary motor area, however, was more active during the replay than when experiencing a genuine hallucination, suggesting that the supplementary motor area is involved in recognizing that inner speech came from your own mind.
There are still some big hurdles in understanding inner speech. It’s difficult to study, because it’s an inherently private process.
How do you get a baseline brain scan of somebody not experiencing inner speech? How do you know for sure someone’s experiencing inner speech? Perhaps what’s really needed is a way for scientists to read our minds—which isn’t quite as ridiculous as it sounds.
Do people who are born deaf have an inner voice?
It turns out that people who are born deaf have an inner voice, just not an auditory one. Instead, their inner voice takes the form of communication that they use – sign. Studies have shown that the same areas of the brain used for our inner voice were activated when signers thought to themselves in sign.
Soon we won’t need a voice; they’ll be reading our minds
Before you make a little hat out of aluminum foil and set up camp in the basement, though, don’t worry—in truth, it’s not that easy. Our brains contain over 100 billion neurons; that’s simply too much data to interpret.
Despite this, scientists are making headway on deciphering our brains. Last year, researchers at Yale showed participants images of people and then used their brain activity to reconstruct them. Maybe it is time for aluminum foil hats after all.
Similarly, researchers have attempted to reconstruct video footage from the brain activity of people watching it. The results aren’t perfect, but they do get the broad image right, in a horror film kind of way.
Mind reading’s an unsettling concept, but it could prove useful (provided it’s not used in making another tacky movie like Mel Gibson’s “What Women Want”). We could read the brain activity of the paralyzed and use it to instruct a wheelchair which way to move or even directly translate the thoughts of people who can’t speak into audio.
Unfortunately—or fortunately, if you have an embarrassing medical problem—we are far from achieving total mind reading. Studies so far rely on somebody lying still in a giant fMRI machine and building a prior database of brain patterns, which is hardly plausible for use on the general population. Yet.
Our lives are accompanied by an internal monologue that performs important cognitive functions, but most of us wouldn’t appreciate it being broadcast live. Luckily, for now, we can feel safe with the knowledge that our inner thoughts are private, but for how long is uncertain.