Toward an Emotional Individual Motor Signature

Abstract

Bodily expression of felt emotion has been documented in the literature. However, it is often associated with high motor variability between individuals. This study aimed to identify individual motor signature (IMS) of emotions. IMS is a new method of motion analysis and visualization able to capture the subtle differences in the way each of us moves, seen as a kinematic fingerprint. We hypothesized that the individual motor signature would be different depending on the induced emotional state and that an emotional motor signature of joy and sadness common to all participants would emerge. For that purpose, we elicited these emotions (joy, sadness, and a neutral control emotion) in 26 individuals using an autobiographical memory paradigm, before they performed a motor improvization task (e.g., the mirror game). We extracted the individual motor signature under each emotional condition. Participants completed a self-report emotion before and after each trial. Comparing the similarity indexes of intra- and inter-emotional condition signatures, we confirmed our hypothesis and showed the existence of a specific motor signature for joy and sadness, allowing us to introduce the notion of emotional individual motor signature (EIMS). Our study indicates that EIMS can reinforce emotion discrimination and constitutes the first step in modeling emotional behavior during individual task performances or social interactions.

Keywords: emotion; individual motor signature; kinematics; mirror game; movement.

FIGURE 1

Experimental device showing one participant engaged in the improvizational motor task (i.e., the adapted Mirror Game, cf. Noy et al., 2011).

FIGURE 2

Individual motor signatures (IMS) of each participant in the similarity space, for the three tested emotional conditions neutral (in blue), joy (in yellow), and sad (in red). The nine small dots in each ellipse correspond to the nine individual trials by emotional condition. X-axis and Y-axis represent the first two dimensions of the multidimensional scaling analysis (MDS), proper to each participant (see text for details).

FIGURE 3

Schematic example of ellipses of the three conditions (IMS) with intra-emotion distances (in black) and inter-emotion distances (in gray) for one participant. To compute the intra-emotion similarity index, the mean distance in black was calculated for each condition. To compute inter-emotion similarity index, the mean distance in gray was calculated between each condition. For clarity, the interaction of only three trials per condition is displayed (represented with dots), instead of nine trials in the actual experiment.