Practice and Retention: A Unifying Analysis
John R. Anderson
What is the strength of a memory trace which has received various practices at times
tj in the past? The Strength Accumulation Equation proposes Strength = tj-d where
the summation is over the practices of the trace. This equation predicts both the
power law of practice and the power law of retention. This paper reports the fits of
the predictions to five experiments derived from the Strength Accumulation Equation.
Across these experiments, participants receive as many as 200 trials of practice
distributed over intervals as long as 400 days. The experiments also vary whether
participants are just practicing retrieving an item or practicing applying a relatively
complex rule. A model based on this equation successfully fits all the data if we
assume slowed passage of psychological time after the experimental session. The
Strength Accumulation Equation is compared to other conceptions of the retention
function and the relationship of the retention function to the practice function.
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