Retroactive inhibition in free-recall learning of categorized lists

Abstract

Two successive lists of 35 nouns representing 7 conceptual categories were presented for 4 trials each. For half of the S s different examples of the same categories appeared in the two lists; for the other half different categories were represented by the words in the lists. The experimental S s recalled the words either immediately after learning List 2 or after a 20-min delay. One-third of the S s recalled both lists at the same time, 1/3 recalled List 1 and then List 2, and 1/3 recalled List 2 before recalling List 1. Significant retroactive inhibition (RI) was obtained for both the Same and Different conditions, and the amount of RI was significantly greater in the Same condition. The RI in the Different condition resulted from the loss of whole categories while the RI in the Same condition resulted from the loss of both whole categories and specific words within categories. There was significantly less RI when both lists were recalled together than when they were recalled separately. Although there was a general increase in performance over the 20-min interval, there was no evidence of spontaneous recovery. It was concluded that the amount of RI obtained in free recall is directly related to the similarity of the organizational cues used for organizing the words into higher-order units.