Learning to carve nature at its joints: the development of hierarchical event structures in perception and action

Adults have a semantically discretised, event-based perception of reality – such that events and goals are both hierarchically structured and have a beginning, middle and end. Here, we consider how we first develop the ability to parse reality into discrete units - as we learn, to use Plato’s phrase, to ‘carve nature at its joints’. Central to this process is the ability to make predictions on hierarchical timescales. We consider two aspects of predictability: first, a child’s capacity to use predictability to inform how they observe events as they unfold; and second, children’s capacity to actively generate predictable sequences of behaviour. We highlight two themes that are, we argue, common across both observation and action. First, flat (i.e. non-hierarchical) predictability initially increases over development, before decreasing as hierarchical predictability (i.e. nested, multi-level goals) increases. Second, learnt regularities in low-level environmental data (e.g., movement, contrast, over fine-grained timescales) feed into our internal predictions of higher-order events (e.g., goals, over more coarse-grained timescales). In sum, over development, children construct increasingly elaborate hierarchies in the observation and generation of events.