Intertrial Proactive Inhibition in Short-Term Memory

Abstract

Ss were given three trials of either a letter-trigram or a word-trigram. Immediately after the trigram a 3-digit number was presented from which S counted backwards by 3s for 8 sec., after which S recalled the trigram. On the fourth trial either the same kind of material as presented before was used or a different kind of material. For letter-trigrams, the recall interval in the fourth trial was either 5, 11, or 17 sec. For word-trigrams, only 11 sec. was used as the recall interval. To control for novelty, another group had letter-trigrams for four trials, but in the fourth the trigram was typed in red. Similarity of the material presented on the preceding trials interfered with recall of both letter- and word-trigrams. In addition, the hypothesis that the probability of interference of previous similar materials on the fourth trial would increase with longer recall intervals was supported for letter-trigrams. Novelty did not affect recall.