The pupil as a window to the mind’s eye: Greater emotionality of episodic imagery than verbal visualisation of rewarding activities

Episodic imagery has been shown to amplify emotion more than abstract verbal representations. This may prove useful for clinical interventions aiming to motivate adaptive behaviours. However, most findings rely on self-report measures and verbal control conditions not designed to actively prevent automatic engagement in episodic imagery. We thus investigated the difference in emotionality between Episodic Imagery (EI) and Verbal Visualisation (VV) using pupil dilation as a physiological measure of emotional arousal. A sample of 75 participants listened to audio recordings describing activities in a positive manner. Subjects were randomly assigned to the EI or VV condition. Participants in the EI condition imagined performing the described activity, while participants in the VV condition visualised the words constituting the descriptions. As predicted, EI led to greater pupil dilation than VV, independent of mental effort. Self-reported anticipatory reward assessed throughout the task was also greater for EI than VV, yet no difference was found for arousal, anticipated reward or motivation. Our findings extend previous work demonstrating the property of episodic imagery to amplify emotion to a physiological level using pupillometry. However, we did not find a transfer to motivation, which is in line with previous studies using verbal control conditions for episodic imagery.