Poster #193 - Social Factors Influence the Meaning of the ‘Back-of-Hand’ Gesture in Adults and Infants: EEG Study

• In Event: 1-005 - Poster Session 01
  In Poster Session: PS 01 Section - Social Cognition

Integrative Statement

The role of the Mirror Neuron System (MNS) in goal-directed action understanding remains equivocal. According to the direct-matching theory, motor activation while observing an action relies on having the corresponding motor repertoire and leads to the understanding of that action (Rizzolatti & Craighero, 2004). Conversely, the predictive coding theory postulates that motor activation is due to the anticipation of the action’s goal (Kilner et al., 2007). While these theories attribute different roles to the MNS in goal-directed action observation, it is unclear whether social-communicative actions also activate the MNS. Social-communicative actions do not necessarily lead to the manipulation of an object or its attainment, and may differ in meaning with varying contexts. Infant electroencephalography (EEG) studies have hitherto focused on the classic instrumental actions such as reaching and grasping. They found mu rhythm desynchronization around central scalp areas for actions performed by the self and to those observed. Here we asked whether social-contextual information could overturn an action interpretation from meaningless to meaningful. We hypothesize that contextual factors may render an action meaningful even if it is not often executed, as in the case of the back-of-hand gesture in infants. We placed this gesture, typically used as control (Southgate et al., 2010), either into a social context ascribing it a ‘request’ gesture, or into a non-social context, remaining meaningless.
The stimuli comprised of short videos of social and nonsocial situations, where a person displayed the back-of-hand gesture. The EEG was recorded from a group of adults and 9-month-old infants while they watched the videos. Infants also performed an action execution task, where they grasped colourful objects. We looked at mu activity (8-13Hz for adults; 6-9Hz for infants) during action execution (only infants) and in both the social and nonsocial conditions during action observation (both groups).
In the adult group, we found main effects of condition, time (baseline vs. test phase) and location, with greater mu desynchronization during the test phase in the social condition. Further t-tests revealed a stronger mu desynchronization in the central and parietal regions for the social condition compared to the nonsocial condition and compared to the baseline (all ps < 0.05; N=15). In infants, there was significant mu attenuation in the parietal region compared to the baseline during action execution (p < 0.01 after Bonferroni correction; N=21). For action observation, there was greater mu desynchronization in the right centro-parietal region for the social condition (N=18) compared to the nonsocial condition (N=18) and compared to the baseline (all ps < 0.05). Occipital mu activity was not significant in both the adult and infant samples.
These results provide evidence for the ‘prediction theory’ of action understanding. They further suggest that the MNS is involved in predicting social action goals, distant from objects. The infant data provide some support for early onset of social action understanding from a third person perspective (Elsner et al., 2014; Liszkowski, 2014).

Authors

• Sriranjani Karthik, University of Hamburg
  Presenting Author

• Eugenio Parise, Lancaster University
  Non-Presenting Author

• Ulf Liszkowski, University of Hamburg
  Non-Presenting Author