Mental-addition development of children classified as mentally handicapped

The training experiment with 30 mentally handicapped children tested two models of mental-arithmetic development. Contrary to an associative learning model and consistent with a schema model, children's initial responses to a mental-addition task appear to be the product of a mechanical prescription, such as simply stating one of the addends. The evolution of mental-addition errors was not linked to practicing incorrect answers; mental-addition errors appear to be more an error of method than an error of recall. Moreover, experimental subjects mastered both practiced and unpracticed combinations involving zero and one, which indicates that they learned relationships, not specific associations: