Dissociating Language and Thought in Human Reasoning

Abstract

What is the relationship between language and complex thought? In the context of deductive reasoning there are two main views. Under the first, which we label here the language-centric view, language is central to the syntax-like combinatorial operations of complex reasoning. Under the second, which we label here the language-independent view, these operations are dissociable from the mechanisms of natural language. We applied continuous theta burst stimulation (cTBS), a form of noninvasive neuromodulation, to healthy adult participants to transiently inhibit a subregion of Broca’s area (left BA44) associated in prior work with parsing the syntactic relations of natural language. We similarly inhibited a subregion of dorsomedial frontal cortex (left medial BA8) which has been associated with core features of logical reasoning. There was a significant interaction between task and stimulation site. Post hoc tests revealed that performance on a linguistic reasoning task, but not deductive reasoning task, was significantly impaired after inhibition of left BA44, and performance on a deductive reasoning task, but not linguistic reasoning task, was decreased after inhibition of left medial BA8 (however not significantly). Subsequent linear contrasts supported this pattern. These novel results suggest that deductive reasoning may be dissociable from linguistic processes in the adult human brain, consistent with the language-independent view.

Continuous Theta-Burst Stimulation on the Left Posterior Inferior Frontal Gyrus Perturbs Complex Syntactic Processing Stability in Mandarin Chinese

“…However, significant stimulation effects appeared in different behavioral indices of different syntactic tasks. For instance, no accuracy differences but differences in eye-tracking indices could be found during a syntactic ambiguity resolution task after cTBS ( Acheson & Hagoort, 2013 ), whereas accuracy was significantly decreased for a grammaticality judgment task after cTBS to LpIFG ( Coetzee et al, 2023 ). In our study, neither Δ d ′ nor Δ RT showed statistical differences in the conditions.…”

“…As a convenient protocol for stimulating the brain for a relatively short period (∼40 s), cTBS has been utilized in several recent studies to establish the causal link between the neural activity of LpIFG and syntactic processing ( Acheson & Hagoort, 2013 ; Coetzee et al, 2023 ). However, significant stimulation effects appeared in different behavioral indices of different syntactic tasks.…”

Deductive Reasoning Skills in Children Aged 4–8 Years Old

“…Young children’s general intelligence (g factor) plays a significant role in their cognitive skills progress ( Almamari and Traynor 2021 ; Gomes et al 2014 ; Panizzon et al 2014 ). Moreover, language is central in the operations of children’s complex cognitive tasks, especially in deductive reasoning ( Coetzee et al 2023 ). It is also possible that the country of residence has a stronger influence on educational systems and teaching methods, which in turn affect deductive reasoning skills.…”