Characterizations of Voluntary and Involuntary Imagery in Aphantasia

Aphantasia refers to the condition one is unable to summon visual mental images in minds. However, whether aphantasia loses such ability completely or only the consciousness for image generation is a debated and unsolved issue. To address this question, the present study aimed to characterize aphantasia in voluntary (II) and involuntary imagery (VI). W.S., a woman aphantasia, and her age-, IQ-, attention ability-matched control groups (gender-mixed or gender-matched) were recruited and assessed with four differential threshold tasks (DT). In three DTs, visual mental images were instructed to create voluntarily or involuntarily preceded the DT task varying with imagery duration time (II-0.5s, VI-0.5s and VI-6s). The other is the pure perceptual task (baseline). Systematical impairments were detected in W.S. in VI-6s: in congruent trials, W.S. exhibited extremely lower accuracy rates than controls; in incongruent trials, the deficit was evident in the difference of DT between baseline and imagery condition (DDT). However, no deficit was observed in comparison between W.S. and controls in VI-0.5s and II-0.5s tasks. All these results suggested that aphantasia was entangled in creating mental images voluntarily. As such, more mental resources would be required for image generation in aphantasia and showed difficulty in switching attention from distractor (mental images) to the following perceptual processing. On the other hand, aphantasia may still preserve the II abilities to summon images in minds unconsciously. The present results contribute to our understanding of aphantasia, suggesting that individuals with aphantasia are not completely losing imagery ability, but experience a reduction or absence of spontaneous mental imagery.