Background: Preventing interpersonal violence requires understanding the moral development and determinants of child aggression. Communication about moral values and concerns by parents is theoretically important in this process. We aimed to develop a coding system to measure mothers' communication about morality with young children and test its psychometric properties. Method: The cross-sectional study included a subsample (n = 200) of mothers and their four-year-old children in a population-based Brazilian birth cohort. Mothers and children were filmed while looking at a picture book together, containing events of aggression, taking away without asking, and several prosocial behaviours. Films were transcribed and a coding system, including 17 items, was developed to measure the maternal moral judgements and the explanations communicated to their children. Inter-rater reliability was estimated, and exploratory factor analysis performed. Results: Mothers judged acts of physical aggression as wrong more frequently than taking away material goods without asking; most mothers communicated about the emotional consequences of wrong behaviour with their child. Two latent factors of moral communication were identified, interpersonal moral concern and the expression of material moral concern. There was excellent inter-rater reliability between the two coders. Conclusions: Parent-child book-sharing provides a means to measure maternal communication about morality with their children. The coding system of this study measures both communication about interpersonal moral concern and material moral concern. Further studies with larger samples are suggested to investigate the importance of these dimensions of caregiver moral communication for children's moral development.
Keywords: book-sharing; children; moral communication; moral development; mother–child interaction.