Humans have been expressing thoughts with language for tens (or perhaps hundreds) of thousands of years. It's a hallmark of our species — so much so that scientists once speculated that the capacity for language was the key difference between us and other animals. And we've been wondering about each other's thoughts for as long as we could talk about them.
"The 'penny for your thoughts' kind of question is, I think, as old as humanity," Russell Hurlburt, a research psychologist at the University of Nevada, Las Vegas who studies how people formulate thoughts, told Live Science. But how do scientists study the relationship between thought and language? And is it possible to think without words?
The answer, surprisingly, is yes, several decades of research has found. Hurlburt’s studies, for instance, have shown that some people do not have an inner monologue — meaning they don't talk to themselves in their heads, Live Science previously reported. And other research shows that people don't use the language regions of their brain when working on wordless logic problems.
For decades, however, scientists thought the answer was no — that intelligent thought was intertwined with our ability to form sentences.
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"One prominent claim is that language basically came about to allow us to think more complex thoughts," Evelina Fedorenko, a neuroscientist and researcher at MIT's McGovern Institute, told Live Science. This idea was championed by legendary linguists like Noam Chomsky and Jerry Fodor in the mid-20th century, but it has begun to fall out of favor in more recent years, Scientific American (opens in new tab) reported.
New evidence has prompted researchers to reconsider their old assumptions about how we think and what role language plays in the process.
"Unsymbolized thinking" is a type of cognitive process that occurs without the use of words. Hurlburt and a colleague coined the term in 2008 in the journal Consciousness and Cognition, after conducting decades of research to verify that it was a real phenomenon, Hurlburt said.
Studying language and cognition is notoriously difficult, partly because it's really hard to describe. "People use the same words to describe very different inner experiences," Hurlburt said. For example, someone might use similar words to recount a visual thought about a parade of pink elephants as they would to describe their non-visual, pink elephant-centric inner monologue.
Another issue is that it can be tough to recognize language-free thought in the first place. "Most people don't know that they engage in unsymbolized thinking," Hurlburt said, "even people who engage in it frequently."
And because people are so trapped in our own thoughts and can't directly access the minds of others, it can be tempting to assume that the thought processes that go on inside our own heads are universal.
However, some labs, like Fedorenko's, are developing better ways to observe and measure the connection between language and thought. Modern technologies like functional magnetic resonance imaging (fMRI) and microscopy give researchers a pretty good picture of which parts of the human brain correspond to different functions; for example, scientists now know that the cerebellum controls balance and posture, while the occipital lobe handles most visual processing. And within these broader lobes, neuroscientists have been able to approximate and map more specific functional regions associated with things like long-term memory, spatial reasoning and speech.
Fedorenko's research takes such brain maps into account and adds an active component.
"If language is critical for reasoning, then there should be some overlap in neural resources when you engage in reasoning," she hypothesized. In other words, if language is essential for thinking, brain regions associated with language processing should light up whenever someone uses logic to figure out a problem.
To test this claim, she and her team conducted a study in which they gave participants a word-free logic problem to solve, such as a sudoku puzzle or a bit of algebra. Then, the researchers scanned these folks' brains using an fMRI machine as they worked out the puzzle. The researchers found that the regions of the participants' brains associated with language did not light up as they solved the problems; in other words, they were reasoning without words.
Research like Fedorenko's, Hurlburt's and others show that language is not essential for human cognition, which is a particularly important finding for understanding certain neurological conditions, such as aphasia. "You can kind of take away the language system, and a lot of the reasoning can proceed just fine," Fedorenko said. However, "that's not to say that it wouldn't be easier with language," she noted.
Originally published in Live Science.