Novel online enfacement illusion for investigating self-perception in mental disorders: an experimental study protocol

Abstract

Background: Remote research methods and interventions for mental health disorders have become increasingly important, particularly for conditions like eating disorders (EDs). Embodiment illusions, which induce feelings of ownership over another person?s body or body parts, offer valuable insights into the mechanisms underlying self-perception issues in EDs and potential interventions. However, existing research using these illusions has been limited to face-to-face settings. We illustrate a novel online protocol to induce the enfacement illusion (embodiment illusion principles applied to one's face) in an ED-based sample.

Methods: Participants complete a 2-hr virtual session with a researcher. First, baseline trait/state ED psychopathology measures and a self-face recognition task occur. Second, participants experience two testing blocks of the enfacement illusion involving synchronously and asynchronously mimicking a pre-recorded actor's facial expressions. After each block, subjective and objective enfacement illusion measures occur alongside state ED psychopathology reassessment.

Discussion: Successfully inducing enfacement illusions online could provide an affordable, accessible virtual approach to further elucidate the mechanistic role of self-perception disturbances across psychopathologies such as EDs. Moreover, this protocol may represent an innovative, remotely-delivered intervention strategy, as 'enfacement' over another face could update negative self-representations in a cost-effective, scalable manner.

Keywords: Eating disorder; Embodiment illusion; Enfacement illusion; Facial perception; Mental health; Online; Self-perception; Tactile-reduced.

Fig. 1

Example depiction of the classic rubber hand illusion procedure with tactile stimulation (i.e., stroking). A participant’s hand is hidden from their view as they observe a rubber hand placed in their view. Both hands are synchronously stroked. Reproduced, with permission, from [82]

Fig. 2

Example depiction of female stimulation video using facial mimicy. Here, the model alternates between a neutral facial expression (left and right) and smiling facial expression (centre) in 10 s iterations for a duration of 150 s

Fig. 3

Simplified graphic depiction of the experimental procedure for eating disorder populations containing the three main assessment blocks. EAT-26 = Eating Attitudes Test 26-item; BSS = Body Satisfaction Scale; BICI-10 = Body Image Concern Inventory 10-item short version; FAds = Facial Adiposity Scale; FAts = Facial Attractiveness Scale

Fig. 4

Example depiction of the online enfacement illusion procedure showing the synchronous facial mimicry condition with a smiling expression (i.e., tactile-reduced stimulation)