Categories, subcategories, and the attenuation of proactive inhibition in free recall.

In two experiments, "proactive inhibition" was observed in the free recall of a succession of 15-word lists. Recall performancc declined across lists when all lists were drawn from the same taxonomic category (e.g., occupations). But this decline did not appear when the successive lists were drawn from discrete subcategories (such as "professional" and "skilled manual" occupations). The findings clarify the conditions in which proactive inhibition effects in free recall are likely to occur. Specifically, when the set of items on any one list is more homogeneous than the set of items from all lists taken together, "proactive inhibition" will be attenuated.