Effects of practice on component processes in complex mental addition.

Two experiments examined the effects of task practice on the speed of executing the component processes underlying the mental solution of complex addition problems. Componential analyses of Ss' response times in Experiment 1 demonstrated that the component process of carrying was reliably affected by amount of task practice. In contrast, the component processes of encoding single digits and of retrieving correct columnar answers from long-term memory appeared not to have been affected by amount of task practice. Computational feasibility checks indicated that the specificity of the practice effects could be explained by 2 distinct learning mechanisms: strengthening and composition. Results of Experiments 2A and 2B favor a composition explanation. We conclude that the differential practice effects in Experiment 1 are probably due to differential composition of component processes underlying complex mental addition.