CLUSTER: A program for identifying recurrent clusters

Abstract

A new way of analyzing organization in free recall (and other sequences) was recently proposed by Buschke (l976), who showed the clustering in free recall by identifying recurrent clusters of items that were recalled together and were demarcated by different items or clusters on different recall attempts. CLUSTER is a new program for analyzing sequential organization by fmding recurrent groups and subgroups of items that occur together (regardless of order), delineating the specific clusters on each trial to show the development of organization and provide a basis for measuring organization in terms of such clustering. . Description. CLUSTER is an extension ofPellegrino's (l972) program for analyzing subjective organization from one trial to the next, extending Pellegrino's program search for recurrent clusters on any trial by comparing all sequences of items on every trial with those in all subsequent trials. Larger groups are broken up into component subgroups by comparing groupings in Trial I with those in Trials 2, 3 N, groupings in Trial 2 with those in Trials 3, 4 N, and so on until the smallest clusters have been identified. A cluster is identified as a group of items that are recalled together in any order on two or more trials and are demarcated by different items or clusters on different trials. Identifying clusters that recur on any trials shows the recurrence of clusters on more than just the next trial, so that the development and persistence of organization during learning can be analyzed in terms of the basic clustering and higher order organization of clusters. While the main purpose of Pellegrino's (1972) program was to compute the amount of subjective organization in free recall learning (Pellegrino, 1971) without delineating specific clusters, o~r aim is to analyze the actual clustering on all trials, so that the nature of the