Inspired by the anthropology of social policy, this article explores the labyrinth of knowledge forms, politics and morality through which a certain programme for early childhood development (ECD) has unfolded in Brazil. By tracking the materiality of ideas – the actors who defend them, the experiments that back them, and the institutional vectors that assure them legitimacy – I weave together variegated threads from neuroscientists, BBC documentaries and Brazilian politicians to moralised motherhoods, criminal brains and, finally, a surprising appraisal on the diminished cognitive capacity of a whole population. Nurtured in the critical analyses of intensive parenting and correlated discussions on ‘chaotic concepts’, I hope to seize on the Brazilian experience to incorporate a new variable into the cost-benefit equation often used to favour ECD – that of the moral fall-out concerning visions of gender, family and class.