The fourth training school focused on individual differences in social interaction. During the training school, the ESRS learned about developmental processes related to individual differences, with a focus on social, vocal, and motor development. ESRs received training in diagnosing children who differ substantially from others (e.g. those with ASD). They had a hands-on training on computational modelling and connecting multiple data sets and longitudinal analysis. They discussed the issues of co-morbidity; globalisation; representation in research: how to generalise research across contexts; and validation of measures across populations.