Perceptual illusion of body-ownership within an immersive realistic environment enhances memory accuracy and re-experiencing

Abstract

Our bodies provide a necessary scaffold for memories of past events. Yet, we are just beginning to understand how feelings of one's own body during the encoding of realistic events shape memory. Participants formed memories for immersive, lifelike events by watching pre-recorded 3D videos that involved a first-person view of a mannequin's body through head mounted displays. We manipulated feelings of body ownership over the mannequin using a perceptual full-body illusion. Participants completed cued recall questions and subjective ratings (i.e., degree of reliving, emotional intensity, vividness, and belief in memory accuracy) for each video immediately following encoding and one week later. Sensing the mannequin's body as one's own during encoding enhanced the following factors: memory accuracy across testing points, immediate reliving, delayed emotional intensity, vividness, and belief in memory accuracy. These findings demonstrate that a basic sense of bodily selfhood provides a crucial foundation for the accurate reliving of the past.

Keywords: Machine perception; Memory structure.

Graphical abstract

Figure 1

Screenshots of an example video: Hagaparken Each immersive video involved a first-person view of a mannequin's body that was continuously stroked with the Styrofoam ball as an event unfolded within the scene. Participants watched videos through an HMD and felt strokes on their actual torso either synchronously or asynchronously with the strokes in the video. Note that footage from only one eye is shown here. Actual stimuli consisted of two videos taken from slightly different positions corresponding to a left and right eye centered in the middle of the HMD to create a stereoscopic effect.

Figure 2

Illusion induction questionnaire ratings (A) Average illusion statement ratings were corrected for susceptibility to demand characteristics by subtracting average control statement ratings from average illusion statement ratings separately for each conditions. The synchronous condition was associated with higher ratings, indicating that participants felt a greater sense of ownership over the mannequin's body relative to the asynchronous condition. (B) Average statement ratings that assessed illusion strength (I1-I3) were consistently higher in the synchronous compared to asynchronous condition. In contrast, average ratings pertaining to control statements (C1-C3) did not differ between conditions. Plot shows means ± SE. p = .001.

Figure 3

Cued recall accuracy The synchronous condition was associated with increased cued recall accuracy, relative to the asynchronous condition. Plot shows means ± SE. p = .03.

Figure 4

Correlation between illusion strength and cued recall accuracy in the synchronous condition A Spearman's rank order correlation found that the strength of the full body illusion was marginally positively correlated with the ability to accurately retrieve details of events encoded with synchronous visuotactile stimulation. p = .06.

Figure 5

Subjective ratings (A–D) (A) Reliving ratings were higher in the synchronous compared to asynchronous conditions at immediate testing. Emotional intensity (B), vividness (C), and belief in memory accuracy, (D) were higher in the synchronous compared to asynchronous conditions at delayed testing. Plot shows means ± SE. All p's < .03