Dissociating language and thought in human reasoning

Abstract

AbstractWhat is the relationship between natural language and complex thought? In the context of complex reasoning, there are two main views. Under the first, language is central to the syntax-like combinatorial operations necessary for complex reasoning. Under the second, these operations are independent of the mechanisms of natural language. We used noninvasive neuromodulation, in the form of continuous theta burst stimulation, to transiently inhibit Broca’s area, a region associated in prior research with parsing the syntactic relations of natural language, and dorsomesial frontal cortex, a region previously described as core for logical reasoning. The dissociative hypothesis of language and deductive reasoning predicts an interaction between stimulated areas and tested functions, which we observed. Transient inhibition of Broca’s area significantly disrupted linguistic processing without affecting deductive reasoning. The reverse pattern was seen for transient inhibition of dorsomesial frontal cortex, albeit not reaching significance. These results are evidence for the independence of abstract complex reasoning from natural language in the adult brain.