Figure 1.

Experimental design. Structure of the protocol with four blocks alternating “in-phase/anti-phase.” Each block is divided into 10 trials (left). Each trial starts with the participant instructed to synchronize with the sound of a metronome for 3 s. Then, the participant interacts with the avatar according to the instruction (e.g., “in-phase”). At the end of the trial, two questions appear directly on the screen. First, the impression of the participant on the competitive or cooperative behavior of the avatar, and second regarding the humanness of the avatar (right). Shown are screenshots of what participants could see (top). In-phase refers to synchronized movements using homologous muscles of the limbs and anti-phase to alternating movements (180° out of phase). Cooperative and competitive refer respectively to the behavior of the virtual partner when it has shared or conflicting goals with the human participant.