Abstract: S ummary . Previous results are reviewed and two series of experiments on learning are described, one carried out in the laboratory, and the other in educational institutions. Both series use ‘conversational’ systems which allow mental activities to be described in terms of dialogue and behaviour. Several types of result are reported: (a) the significance of understanding; (b) the existence of, and variations in, learning strategies; (c) the effect of matching and mismatching a teaching strategy to an individual's learning strategy; (d) the nature and classification of cognitive style; and (e) transfer effects and ‘learning to learn.’ A theoretical basis is developed for a classification of learning styles.