Separation of storage and retrieval factors in free recall of clusterable pairs

Presents a 2-factor hypothesis for the spacing effect in free recall of 2-item clusters: (a) The information and storage of clusters is more likely with small within-category spacing, and (b) the retrieval of clusters is more likely with large within-category spacing. The hypothesis was studied on 3 levels of increasing theoretical sophistication; Ss were 76 undergraduates. Central to all the analyses was the representation of pair-clustering data in terms of basic events in an underlying sample space. At the lowest level, descriptive measures of category recall are shown to vary with spacing in a complex manner that is consistent with, but in no way demonstrative of, the 2-factor hypothesis. Next, a simple statistical model is formulated that permits measurement of hypothetical storage and retrieval contributions to pair clustering. A study of these 2 quantities provides direct support for the 2-factor hypothesis. Finally, the 2-factor hypothesis is embedded in a multilevel Markov model for pair clustering that postulates separate short- and long-term memory states. The model provides a good account of trial-to-trial changes in the basic events of pair clustering. (29 ref)