Cognitive development is often characterized in term of dis-continuities, but these discontinuities can sometimes be appar-ent rather than actual and can arise from continuous develop-mental change. To explore this idea, we use as a case study thefinding by Stager and Werker (1997) that children’s early abil-ity to distinguish similar sounds does not automatically trans-late into word learning skills. Early explanations proposedthat children may not be able to encode subtle phonetic con-trasts when learning novel word meanings, thus suggestinga discontinuous/stage-like pattern of development. However,later work has revealed (e.g., through using simpler testingmethods) that children do encode such contrasts, thus favoringa continuous pattern of development. Here we propose a prob-abilistic model describing how development may proceed ina continuous fashion across the lifespan. The model accountsfor previously documented facts and provides new predictions.We collected data from preschool children and adults, and weshowed that the model can explain various patterns of learningboth within the same age and across development. The find-ings suggest that major aspects of cognitive development thatare typically thought of as discontinuities, may emerge fromsimpler, continuous mechanisms.
