Infants' Attention to Briefly Presented Emotional Expressions

The capacity to rapidly detect emotion from facial expressions has been proposed as an evolutionarily adaptive mechanism. Studies have found that infants respond rapidly to facial expressions, particularly those involved with the detection of threat (i.e., fearful and angry expressions). The current study used a behavioral measure to determine whether there are differences in attention (first fixation duration and dwell time) to backward-masked faces expressing specific emotions (anger, fear, happy, and neutral) at specific stimulus durations (67, 167, 567, or 767 ms). Data were collected from 103 (47 male) 7.5-month-old infants (mean age = 226 days). There was a main effect of stimulus duration on the first fixation duration, such that the two shorter presentation durations had longer first fixations than the two longer presentation durations. For total dwell time, there was a main effect of stimulus duration and a main effect of emotion. The main effect of stimulus duration was due to a longer dwell time in the 167 ms duration than the other durations. The main effect of emotion indicated that across the four stimulus durations, there were greater dwell times to the fearful and happy faces, when compared to the neutral condition. While this evidence is consistent with previous findings of infants' rapid detection of fearful expressions, the rapid response to happy expressions argues for a more general emotion-detection advantage than a threat-detection advantage.