Previous research reports mixed results concerning infants’ differential interest for a specific age group. Most of these findings are based on studies using static photographs and drawings as stimuli. Moreover, only behavioral data were used to investigate infants’ attentional preferences. In the present study, we showed video sequences of differently aged models (peers, 3.5-year-olds, and adults) manipulating an object, and measured heart rate as an objective psychophysiological measurement of infants’ attention, in addition to looking time and banging rate. The results showed that 12-month-olds preferred watching older children's object-related actions compared to those of peers and adults, but 6- and 9-month-olds did not. In subsequent control experiments, alternative explanations that this preference relied merely on the visual appearance or a higher activity level of older children were excluded. We explain this observed developmental shift by the increasing importance of social learning and object use at this age. Thus, 12-month-olds prefer watching more knowledgeable individuals who provide an action repertoire that infants of this age are about to develop.