tl;dr-ELT

If you’ve ever stopped to think about it, you might assume that language & thought are separate—that we think first & then find words. But a new 2025 fMRI study from the University of Tokyo, “Neural basis of linguistic factors involved in thought” (Hino et al., Frontiers in Psychology), suggests they’re more intertwined than we might realise—even when words aren’t spoken at all.

The study

The researchers recruited 18 native signers of Japanese Sign Language (JSL) to investigate whether linguistic structures underpin our reasoning processes. Participants completed two kinds of tasks while in an fMRI scanner:

• A “Reasoning Task” involving visual puzzles under five conditions (Context, Fill-in, Rotation, Sequence & Analogy). These were designed to test linguistic factors such as recursion, propositionality & clause structure—concepts central to Chomsky’s minimalist theory of language [which views human language as a result of an efficient, “perfect” computational system within the human mind that generates structures with the least possible effort] —while controlling for purely visual or spatial reasoning.
• A “Sign Task” using short JSL story videos, assessing natural language comprehension in the visual-manual modality.

The clever design meant that the researchers could compare how brain regions activated for reasoning overlapped with those for language understanding—without relying on spoken or written words.

The findings

The results were striking. Across both reasoning & sign tasks, three distinct neural systems emerged, each linked to a specific linguistic function that also supports abstract thought:

• The recursive system (left & right lateral premotor cortex) allows us to nest one structure inside another—whether in a sentence (“The student [who the teacher praised] won a prize”) or in reasoning (“If A causes B, & B causes C, then A must cause C”).
  This capacity for recursion—building complex hierarchies from simpler elements—has long been proposed as a uniquely human trait (see Hauser, Chomsky & Fitch, 2002). The study shows that this structural “scaffolding” mechanism is used not just for grammar, but for logical reasoning itself.
• The propositional system (left inferior frontal gyrus, or Broca’s area) is involved in creating relations between ideas—for example, linking a subject to an action (“The cat chased the mouse”) or connecting two concepts in reasoning (“Effort leads to success”).
  This system helps us form propositions that express meaning, making it central to both sentence construction & problem-solving.
• The clausal system (bilateral posterior temporal gyri) integrates those individual propositions into coherent wholes. It’s what enables us to follow a storyline, understand cause & effect, or make sense of context—essentially, to move from isolated facts to connected understanding.
  In language learning terms, it’s what allows students to interpret nuance, reference, & discourse flow.

Together, these systems suggest that the same neural machinery that handles complex grammar also helps us think in structured, connected ways. Thought, it seems, is not merely “expressed” through language—it’s built from it.

This lends neuroscientific weight to the long-debated “language of thought” hypothesis (see Chomsky, 2021; Berwick et al., 2013): that linguistic architecture doesn’t just express thought—it enables it. The study echoes earlier findings that Broca’s area is active in both syntactic processing (Sakai, 2005) & complex reasoning, supporting the view that human cognition may be fundamentally linguistic.

Teacher Takeaways?

Once again, no direct implications for classroom practice, but it’s always fun to think of some!

• Highlight structure, not just words. Sentence-building & reasoning share neural territory, so exercises that encourage embedding clauses (“I think that… because…”) may strengthen both syntax & critical thinking [something we’re sorely in need of– in any language!].
• Encourage multimodal expression. Whether learners speak, write, or sign, the same core systems appear to scaffold meaning. Visual storytelling or gesture-based tasks might engage the same linguistic reasoning networks.
• Reframe “grammar drills”. Rather than rote form practice, frame grammar as a tool for complex thought—helping students articulate cause, contrast, & condition with precision.

What do you think—does language shape how your students think, or do they think their way into language?