Figure 1.

Stimuli and procedure in the imitation and passive observation tasks. Imitation (a) Top: Pictures showing an actress performing five different emotional facial expressions. Bottom: Time line of two trials: pictures were presented for 2.5 s, followed by a “Relax” label again for 2.5 s. (175 pictures, 35 per expression). Participants were asked to imitate the facial expressions observed and to relax their face during the relax label. Passive observation (b) Top: pictures showing exemplars of the five valence categories. Bottom: Time line of two trials: pictures were presented for 6 s each, followed by a blank screen for 3 s (100 pictures, 20 per valence category)