Studying the Link Between Inter-Speaker Coordination and Speech Imitation Through Human-Machine Interactions

According to accounts of inter-speaker coordination based on internal predictive models, speakers tend to imitate each other each time they need to coordinate their behavior. According to accounts based on the notion of dynamical coupling, imitation should be observed only if it helps stabilizing the specific coordinative pattern produced by the interlocutors or if it is a direct consequence of inter-speaker coordination. To compare these accounts, we implemented an artificial agent designed to repeat a speech utterance while coordinating its behavior with that of a human speaker performing the same task. We asked 10 Italian speakers to repeat the utterance /topkop/ simultaneously with the agent during short time intervals. In some interactions, the agent was parameterized to cooperate with the speakers (by producing its syllables simultaneously with those of the human) while in others it was parameterized to compete with them (by producing its syllables in-between those of the human). A positive correlation between the stability of inter-speaker coordination and the degree of f0 imitation was observed only in cooperative interactions. However, in line with accounts based on prediction, speakers imitate the f0 of the agent regardless of whether this is parameterized to cooperate or to compete with them.