Children are much more likely to benefit from instruction when they are ready to incorporate new knowledge into their existing knowledge base. But can we detect such readiness? In a series of studies, we investigated this critical component of the interactional nature of the learning process. In the first study, we assessed whether adults are able to identify children who are receptive to instruction. Adults were presented with video tapes of pairs of children solving mathematics problems and asked to identify the receptive child (i.e. the child who later actually learned) in each pair. Adults were able to determine which children were receptive. In a second study, we attempted to train adults to use previously established criteria of learning readiness to identify these children. Although the adults only relied on these criteria for about half of their decisions, when they used these criteria, they were highly successful at identifying which children were receptive to instruction. Finally, in a third study, we showed adults video tapes of different children and we obtained comparable results as in Studies 1 and 2. In conclusion, we found that adults can detect readiness to learn in children and thus can be in a position to deliver instruction at optimal times.