How Does The Brain Reason When Words Disappear?

Do we think using words? A new study has shown that people who have lost much of their ability to speak are still able to reason normally. This finding challenges one of the oldest ideas in philosophy and reveals that the brain can think without relying on language.

For centuries, philosophers and scientists have debated a fascinating question: can we think without using words? When we solve a logic problem, perform a mental calculation, or reach a conclusion, is our brain actually "talking to itself"? Or does a system of thought exist that is independent of language?

A new study used modern neuroimaging techniques and analyzed individuals with severe language impairments to investigate this question; the results could change how we understand human thought.

The researchers examined two types of reasoning. The first is deductive reasoning, in which we reach a logical conclusion based on known information. For example: "All mammals have a heart. A dog is a mammal. Therefore, a dog has a heart."

The second is inductive reasoning, which occurs when we observe various examples and formulate a general rule, such as noticing that the Sun rises every day and concluding that it will rise again tomorrow. Both are part of our daily lives and are fundamental to learning, planning, and making decisions.

To discover how the brain carries out these tasks, scientists used functional magnetic resonance imaging (fMRI), a capable scan of which shows brain regions become more active while a person performs a specific mental activity. Healthy volunteers solved various logic problems while their brains were being monitored.

In addition, the researchers evaluated individuals with severe aphasia, a condition resulting from brain injury that profoundly impairs the ability to understand or produce language. If language were indispensable for logical reasoning, these individuals should have experienced significant difficulty in solving the problems.

The results surprised the researchers. During the tests, the brain areas responsible for language remained virtually inactive while the participants solved logical problems. Even more striking, the individuals with aphasia, despite facing enormous challenges in speaking and understanding sentences, were able to complete the logical reasoning tasks with a level of performance very similar to that of individuals without language impairments.

This indicates that the brain can continue to reason even when its capacity to use words is severely compromised.

Scientists have also discovered that different forms of reasoning utilize distinct brain circuits. Inductive reasoning activated regions associated with planning, attention, and general problem-solving. Deductive reasoning, by contrast, recruited a different, specific set of brain areas, distinct both from language-related regions and from those involved in other cognitive tasks. In other words, the brain appears to possess specialized systems for different ways of thinking.

These findings reinforce the idea that logical thought does not necessarily depend on language. Although words are essential for communicating ideas, teaching, and sharing knowledge, they may not be the "engine" of reasoning. Instead, our brain may employ a kind of internal language of its own, composed of mental representations that transcend words.

If this hypothesis continues to be supported by further research, it could transform our understanding of intelligence, learning, and child development, and even inform how we build artificial intelligence systems capable of reasoning in a manner similar to humans.

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Evidence from formal logical reasoning reveals that the language of thought is not natural language

Hope Kean, Alexander Fung, Paris Jaggers, Jason Chen, Joshua S. Rule, Yael Benn, Joshua B. Tenenbaum, Steven T. Piantadosi, Rosemary A. Varley, and Evelina Fedorenko

Proceedings of the National Academy of Sciences. July 6, 2026, Vol. 123 | No. 28

DOI: 10.1073/pnas.2520095123

Abstract: 

Humans are endowed with a powerful capacity for inductive and deductive logical thought: we easily form generalizations based on a few examples and draw conclusions from known premises. Humans also arguably have the most sophisticated communication system in the animal kingdom: natural language allows us to express complex and structured meanings. Some have therefore argued for a tight relationship between complex thought and language, postulating that reasoning, including logical reasoning, relies on linguistic representations. We systematically investigated the relationship between logical reasoning and language using two complementary approaches. First, we used noninvasive brain imaging (fMRI) to examine neural activity as healthy adults engaged in logical reasoning tasks. And second, we behaviorally evaluated logical abilities in individuals with extensive lesions to the language brain areas and consequent severe linguistic impairment. Our findings reveal that the language brain network is not engaged during logical reasoning, and patients with severe aphasia exhibit intact performance on logic tasks. Instead, inductive reasoning recruits the domain-general multiple demand network implicated broadly in goal-directed behaviors, whereas deductive reasoning draws on brain regions that are distinct from both the language and the multiple demand networks. Together, these results indicate that linguistic representations are neither utilized nor required for inductive or deductive logical reasoning.