No evidence for a special role of language in feature-based categorization

Abstract

The relationship between language and human thought is the subject of long-standing debate. One specific claim implicates language in feature-based categorization. According to this view, language resources facilitate object categorization based on a certain feature (e.g., color). Specifically, it is hypothesized that verbal labels help maintain focus on a relevant categorization criterion and reduce interference from irrelevant features. As a result, language impairment is expected to affect categorization of items grouped according to a single feature (low-dimensional categories, e.g., Things that are yellow), where many irrelevant features need to be inhibited, more than categorization of items that share many features (high-dimensional categories, e.g., Animals), where few irrelevant features need to be inhibited. In two behavioral studies with individuals with aphasia, we failed to find consistent support for the role of language in low-dimensional categorization. We also collected fMRI data from healthy adults and observed little activity in language-responsive brain regions during both low-dimensional and high-dimensional categorization. Combined, these results demonstrate that the language system is not implicated in object categorization. Our work adds to the growing evidence that, although language may assist in accessing task-relevant information (e.g., instructions), many cognitive tasks in adult brains proceed without recruiting the language system.