Simulation in the 'Blind' mind: Examining unconscious mental imagery in aphantasia

Aphantasia is the absence of conscious mental imagery, but it is unclear to what extent aphantasia also implicates unconscious mental imagery. Embodied theories of concept knowledge propose that word meaning involves simulation of sensory and motor experiences; thus, examining simulation can refine our understanding of imagery deficits in aphantasia and clarify whether simulation shares mechanisms with conscious and/or unconscious mental imagery. In the present study we examined whether individuals with aphantasia show sensorimotor simulation effects during language processing. We recruited 104 aphantasics and 104 age-, gender-, and education-matched controls who completed two semantic processing tasks, a parity judgement task, and a series of mental imagery questionnaires. We observed simulation effects (i.e., faster responses to words associated with more sensorimotor experience) with both aphantasia and control participants. Our results suggest that simulation during semantic processing can occur in the absence of conscious mental imagery. The findings show that unconscious mental imagery, by way of simulation, may be preserved in aphantasia. The findings also limit the extent to which conscious mental imagery and sensorimotor simulation are likely to share underlying mechanisms.