A beautiful day in the neighborhood: what factors determine the generation effect for simple multiplication problems?

In four experiments, we examined the generation effect for the free recall of simple multiplication answers. Large-product-size problems showed a consistent generation-effect advantage over small-product-size problems, except when each answer was generated twice, via two different sets of operands (Experiment 2). Also, measures of problem-solution time and strategy use accounted for the large-product-size advantage. Across experiments, however, small-product-size problems (but not large-product-size problems) showed considerable variation in the size of their generation effect. We discovered that solving small-product-size problems via direct memory retrieval increased the episodic recall probability of other problems that were near neighbors to the generated answer, and we attribute this result to a spreading activation mechanism in semantic memory. A measure of neighbor activations, combined with RT to solve each problem, accounted for 51% of the observed generation-effect variance.