Angelina G. Makarova

Background. The concept of body schema continues to evolve, and the taxonomy of body representations remains debated. Two well-established paradigms provide experimental access to it: the rubber hand illusion (RHI), which modifies the body schema by incorporating a new object into it, and the hand laterality judgment task (HLJT), which requires participants to determine the laterality of a depicted hand and has been shown to involve mental movement.

Objective. To investigate body schema components using two well-validated experiments, the RHI and the HLJT.

Design. Thirty-one right-handed healthy volunteers aged 18–35 years completed the HLJT and then took part in the RHI. Proprioceptive drift and sense of ownership served as measures of RHI onset, whereas accuracy and response time were recorded in the HLJT. Data analysis was performed with mixed linear modelling.

Results. A cross-analysis of the performance in these tasks revealed distinct associations: 1) between higher accuracy in the HLJT and slower proprioceptive drift in the RHI; and 2) between longer response time in the HLJT and early emergence of the sense of ownership over an artificial hand in the RHI.  We propose that the first pair of variables reflects the strength of the structural body representation (the cognitive level of body schema), whereas the second reflects confidence in those representations (the metacognitive level of body schema).

Conclusion. We observed that participants with better performance on the HLJT showed weaker RHI effects: stronger internal body representations were less susceptible to illusion-related artificial distortions.