Interindividual Differences in Higher and Lower-Order Object-Related Cognition: The Role of Inner Speech

Abstract

The capacity to experience inner speech has been hypothesized to impact cognitive functions like object recognition, abstract thought, and metacognition. However, little is known about how individual differences in the propensity to experience inner speech affect these functions, a relevant topic to address given the wide variation in this trait within the general population. Here, we contribute novel evidence addressing this gap and provide a new tool to measure these individual differences in German-speaking participants. In a first study, we validate the IRQ-G, a German version of the Internal Representations Questionnaire (Roebuck & Lupyan, 2020), offering scales that index the capacity to manipulate visual representations (Representational Manipulation), and the tendencies to experience thoughts in the form of visual and verbal information (Visual Imagery and Internal Verbalization, respectively). In a second study, we observe that participants with higher Internal Verbalization scores respond faster in a word-picture verification task where they match words to images but are more slowed by increases in semantic similarity between the items, relative to those with lower scores. We interpret this as a reflection of more categorical representations being cued in those with more language-reliant thinking during object recognition. In a third study, we present exploratory evidence based on a complex categorization task that more Internal Verbalization relates to slower determinations of response confidence when participants group images that rarely occur in the same context. We additionally offer exploratory evidence that condensed forms of inner speech hamper object recognition but aid abstract thought. Together, our studies highlight the complex and diverse effects of individual differences in inner speech tendencies on noncommunicative cognitive functions and broaden the methodological toolkit of researchers pursuing this line of inquiry in the German-speaking world.