Dissociating voluntary mental imagery and mental simulation: Evidence from aphantasia

Intentional visual imagery is a component of numerous aspects of cognition. Related to visual imagery, mental simulation plays a role in language comprehension: modality-specific regions of the brain are activated as an implicit part of people understanding language. The degree of overlap between the processes underlying conscious, voluntary visual imagery versus less conscious, more automatic mental simulation is unclear. We investigated this issue by having aphantasics (people who are unable to experience conscious voluntary visual imagery) and control participants perform a property verification task in which they were asked whether a property is a physical part of an object (e.g., is mane a physical part of a lion?). We manipulated the false trials so that the two words either were associated (semantically related) but did not form an object-part combination (monkey-banana), or were not associated (apple-cloud). Solomon and Barsalou (Memory & Cognition, 32, 244-259, 2004) demonstrated that word association influenced responses when the words in the false trials were not associated, whereas when they were associated, perceptual measures most strongly influenced the results, indicating mental simulation. In the present study, control participants and aphantasics demonstrated similar evidence of the use of both mental simulation and word association when verifying whether the words formed an object-part combination. These results suggest that visual imagery and mental simulation are at least somewhat separable cognitive processes.