Participants sat about 120 cm from a computer monitor in an acoustically and electrically shielded cabin. They were instructed to focus on a small cross located in the centre of the screen and to avoid any body or eye movements. Stimuli were randomly presented in the centre of the screen for about 900 ms with an ISI of 1300–1900 ms. The stimulus set consisted of 160 high resolution black and white photos of infants expressing neutral or affective (distressed) emotional states. The electroencephalogram (EEG) was continuously recorded and synchronized with the onset of picture presentation. The task consisted of deciding on the emotional content of the picture. The responses were to be made as accurately and quickly as possible by pressing a response key with the right index finger of the right or left hand (to signal distress or well-being). The hand and experimental run orders were counterbalanced across subjects.
