Imagine, for a moment, that you are unable to speak or comprehend a single word. Now, try solving a math problem or untangling a social dilemma. Without that annoying voiceover in your head, what do your thoughts even look or sound like? Would your thoughts grind to a halt without language to guide them? Bertrand Russell, the famed British philosopher, certainly thought so. He argued that language is fundamental to complex thought, suggesting that without it, there could be no real thinking at all.

But nature seems to tell a different story. Chimps, after all, can sometimes outplay humans in strategy games. Crows fashion tools from sticks to snatch prey from hard-to-reach crevices — and I don’t think they go “craw craw craw” in their heads while doing so. They have no words, yet they think — perhaps in ways we don’t yet fully understand.

This question — whether language and thought are fundamentally linked — has been the subject of a lively debate among scientists and philosophers for some time. For Evelina Fedorenko, a neuroscientist at MIT’s McGovern Institute for Brain Research, this question has an easy answer thanks to her decade-long investigations: Language and thought are distinct entities, operating in separate parts of the brain.

You need thinking to have language, but you don’t need language to think and reason. It’s a rare and rather amazing discovery that challenges some of the deepest assumptions about what makes us human.

The Separation of Thought and Language

Fedorenko didn’t always believe this. As a Harvard undergraduate in the early 2000s, she was drawn to the idea — rooted in the teachings of linguist Noam Chomsky — that language is what sets humans apart. She thought our ability to string words into complex sentences was key to how we think. She set out to find the brain region responsible for managing these linguistic and cognitive tasks, hoping to reveal a shared network that powers our advanced reasoning.

But science rarely unfolds the way we expect.

“Language is a prime example of a system based on hierarchical structures: words combine into phrases and phrases combine into sentences. And a lot of complex thought is based on hierarchical structures. So I thought, ‘Well, I’m going to go and find this brain region that processes hierarchical structures of language,’” Fedorenko said in an interview with Scientific American.

Yet, as she dove deeper into her studies, the evidence pointed in the opposite direction, as Fedorenko detailed in a recent perspective article in Nature.

“You find this very clear separation between brain regions that compute hierarchical structures in language and brain regions that help you do the same kind of thing in math or music,” she explains.

Instead of a unified system, Fedorenko discovered that the brain’s language regions stayed quiet while people engaged in non-verbal tasks like solving puzzles or planning their day.

This surprising separation raised a new question: What role, then, does language really play?

The Brain’s Silent Language Regions When Thinking

The evidence supporting Fedorenko’s findings came from two distinct approaches. One method dates back centuries — studying individuals with brain damage, specifically people with severe forms of aphasia. These patients lose much of their ability to understand or produce language, often due to damage to the left hemisphere of the brain.

For these individuals, communication can be nearly impossible. Yet, they can still perform complex cognitive tasks. “You can ask people with global aphasia to solve math problems or perform social reasoning tests, and as long as the instructions are non-verbal, they can succeed,” she says. This shows that even sophisticated thought does not depend on language.

The second method came from modern brain-imaging tools. By mapping the brain regions responsible for language, Fedorenko could test whether those same regions activated during various types of thinking. “We find time and again that the language regions are basically silent when people engage in thinking activities like logic puzzles, memory tasks, or planning,” she says. So, while we rely on language to express our thoughts, the thoughts themselves can exist without words.

It’s a revelation that not only challenges Russell’s idea but also shifts how we think about the mind itself.

A Tool for Communication, Not Thought

If language isn’t essential for thinking, then why did humans develop it? According to Fedorenko, language serves as an efficient tool for communication — a kind of “shortcut for telepathy.” While we can’t read each other’s minds, language allows us to transmit knowledge, thoughts, and ideas from one brain to another. This ability to share complex information likely provided early humans with a huge evolutionary edge.

“And in fact, most of the things that you probably learned about the world, you learned through language and not through direct experience with the world. So, language is very useful,” Fedorenko points out. Whether it’s the latest scientific discovery or the recipe for your grandmother’s secret soup, much of human knowledge is passed down through words.

But this doesn’t mean that language is what directs human thought. The brain contains multiple systems that handle different aspects of cognition — like social reasoning, problem-solving, and memory integration. It’s the combination of these systems, each operating in its own specialized region, that allows for our remarkable cognitive abilities. Language, while powerful in its own right, is just one piece of a much larger puzzle.

The Future of Language Research — And Artificial Intelligence

Surprisingly, advances in artificial intelligence have given scientists like Fedorenko a new way to study language. Large language models, like those powering ChatGPT, offer insights into how linguistic systems might work inside the brain. These models generate complex sentences that are grammatically flawless but lack true understanding or reasoning ability. “They’re not so good at thinking,” Fedorenko says. “Which aligns with the idea that the language system by itself is not what makes you think.”

This distinction between language and thought mirrors what Fedorenko has observed in the human brain. By studying AI systems, researchers hope to better understand how our own minds work, especially in areas that are difficult or unethical to study in humans. For instance, while scientists can’t deprive children of language to study how their brains develop, they can experiment with AI models, training them on different linguistic inputs to see how they learn.

As Fedorenko’s research continues, it may help us unravel more about the brain’s mysterious inner workings. For now, though, one thing is clear: language and thought, once believed to be inseparable, are far more independent than we ever imagined.