Analysis of time required by children for simple additions.

Abstract Children, 9–10 years old, solved all additions with the sum of two positive addends smaller than 14. The cognitive process leading to a solution was described in a model predicting solution times. The model is a revised version of a counter model with two operations: setting and incrementing by one unit. It is assumed that solutions are obtained either by direct retrieval from memory or by a reconstructive process. About 2/3 of the variance of solution times was accounted for by the process model and it was judged to constitute an important starting point and frame of reference for the analysis and understanding of the cognitive process activated when children solve arithmetic problems. The process model was checked against the subjects' verbal descriptions of the strategies used for solving the problems and the errors they made. The verbal descriptions supported the model and gave some additional information about the process studied. The small number of errors did not contribute any unique information but was in general accordance with the process model.