EXPRESS: Development and validation of a pictographic assessment embodiment scale

Embodiment is a complex concept related with the subjective perception of an object as it belongs to the own body. In general, this construct has been evaluated by means of questionnaires but validation studies in other cultures and limitations related with barriers of language received little attention. The purpose of the present investigation was twofold: to validate the factorial structure of Embodiment Questionnaire (EQ) and to construct a pictographic scale (PAE) to measure embodiment without relapse verbal representations. In a first experiment, one hundred and thirty-six participants underwent a Rubber Hand Illusion (RHI) procedure following both congruent and incongruent (control) visuo-tactile stimulations. Then, they evaluated embodiment illusion in EQ using a Likert scale to rate their agreement or disagreement with 27 statements and with a pictographic scale designed to assess their subjective experience of the illusion. Principal components analysis in EQ scores identified four components that emerged in both conditions: Embodiment, Disembodiment, Affect and Deafference. PAE scale was highly correlated with embodiment factor and can differentiate between conditions. In a second experiment, thirty participants underwent the RHI procedure, and they were assessed using PAE and proprioceptive drift. Results indicates a high positive correlation between PAE and post-illusion drift score. These results provide evidence about the consistency of the factorial structure of EQ across cultures and we also provide a new pictographic tool that allows quick measurement of embodiment overcoming language barriers.