Joint language production: an electrophysiological investigation of simulated lexical access on behalf of task partner

This study investigates in a joint action setting a well-established effect in speech production, cumulative semantic interference, an increase in naming latencies when naming a series of semantically related pictures. In a joint action setting, two task partners take turns naming pictures. Previous work in this setting demonstrated that naming latencies increase not only with each semantically related picture speakers named themselves, but also with each picture named by the partner (Hoedemaker, Ernst, Meyer, & Belke, 2017; Kuhlen & Abdel Rahman, 2017). This suggests that speakers pursue lexical access on behalf of their partner. In two electrophysiological experiments (N=30 each) we investigated the neuro-cognitive signatures of such simulated lexical access. As expected, in both experiments speakers naming latency increased with successive naming instances within a given semantic category. Correspondingly, speakers EEG showed an increasing posterior positivity between 250-400ms, an ERP modulation typically associated with lexical access. However, unlike previous experiments, speakers were not influenced by their partners picture naming. Accordingly, we found no electrophysiological evidence of lexical access. To reconcile these findings we pooled behavioral data from five experiments (N=144). Within this large sample we find empirical evidence for partner-elicited interference. Furthermore, our data suggests that speakers may be less affected by their partners naming response in settings with remotely located task partners (as in present experiments). We conclude that speakers do not always represent their partners naming response and that our experimental setting may have limited the participants evaluation of the task as a joint action.