No evidence of theory of mind reasoning in the human language network

Abstract

Language comprehension and the ability to infer others thoughts (theory of mind, ToM) are interrelated during development and language use. However, neural evidence that bears on the relationship between language and ToM mechanisms is mixed. Although robust dissociations have been reported in brain disorders, brain activations for contrasts that target language and ToM bear similarities, and some have reported overlap (Deen et al., 2015). We take another look at the language-ToM relationship by evaluating the response of the language network (Fedorenko et al., 2010), as measured with fMRI, to verbal and non-verbal ToM across 151 participants. Individual-subject analyses reveal that all core language regions respond more strongly when participants read vignettes about false beliefs compared to the control vignettes. However, we show that these differences are largely due to linguistic confounds, and no such effects appear in a non-verbal ToM task. These results argue against cognitive and neural overlap between language processing and ToM. In exploratory analyses, we find responses to social processing in the "periphery" of the language network--right hemisphere homotopes of core language areas and areas in bilateral angular gyri--but these responses are not selectively ToM-related and may reflect general visual semantic processing.