Electrophysiological correlates of attentional capture in joint action.

In joint action, agents are assumed to represent their partner's task to optimize joint performance. However, the neurophysiological processes underlying the processing of the partner's task have not been widely investigated. Pairs of participants were asked to perform a joint version of a visual search task in either a cooperative or a competitive social context. During the task, one agent's neural activity was recorded using electroencephalography (EEG). The alpha-lateralization index was calculated as [(contralateral - ipsilateral)/(contralateral + ipsilateral)] × 100 to examine attentional selection or suppression of the laterally presented stimulus. A negative alpha-lateralization indicates lower alpha-band power over the contralateral sites compared with the ipsilateral sites and was related to attentional selection. A positive alpha-lateralization indicates higher alpha-band power over the contralateral sites compared with the ipsilateral sites and was related to attentional suppression. Behavioural results showed impeded search performance when the partner target was present. Furthermore, EEG time-frequency results showed that the partner target induced a negative parieto-occipital alpha-lateralization, indicating that it captured attention, when the agent target was absent. When the agent target was present, the parieto-occipital alpha-lateralization index was negative for laterally presented partner target in the cooperative and positive in the competitive social context, indicative of attentional capture in the cooperative condition and suppression of the partner target in the competitive condition. In sum, our study showed that humans tune their attentional processing towards a partner target in a joint action task. This attentional tuning was shown to be affected by social context and the presence of the agent's own target.