The relation between young children's physiological arousal and their motivation to help others.

Children are motivated to help others from an early age. However, little is known about the internal biological mechanisms underlying their motivation to help. Here, we compiled data from five separate studies in which children, ranging in age from 18 months to 5.5 years, witnessed an adult needing help. In all studies, we assessed both (1) children's internal physiological arousal via changes in their pupil dilation, and (2) the latency and likelihood of them providing help. The results showed that the greater the baseline-corrected change in children's internal arousal in response to witnessing the need situation, the faster and more likely children were to help the adult. This was not the case for the baseline measure of children's tonic arousal state. Together, these results suggest that children's propensity to help is systematically related to their physiological arousal after they witness others needing help. This sheds new light on the biological mechanisms underlying not only young children's social perception but also their prosocial motivation more generally.