Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)




Considerable current research on memory has focused on the organization of subjects' recall. When the organizational characteristics of a stimulus list are not apparent, subjects will uniquely organize their outputs to facilitate recall. Both Tulving and Bousfield have developed statistics to measure this subjective organization in multitrial free recall experiments. These two measures have been shown to intercorrelate very highly. Substantial correlations are reported between these measures and recall.

During a previous study on subjective organization the recall data from each subject on each trial were scored in such a way that the ordinal position in recall of each word was known. It was then possible to correlate each consecutive pair of trials and obtain the amount of variance shared by the pair. This was called intertrial organization .variance (ITOV) and was shown to be a better measure of subjective organization than previous statistics.

The effects of variable and constant input order on free recall were first examined by Waugh (1961). She concluded that order of presentation did not produce differences in recall, although later studies (e.g., Wallace and Nappe, 1970) have indicated appreciably better recall and organization from constant-order lists.

Tulving (1964) suggested a theoretical model of free recall based upon the assumption that all the items presented to a subject are learned and forgetting explains imperfect recall. This model utilizes contingent probabilities of intertrial and intratrial retention to describe learning curves. Tulving calls this the trial-to-trial (TTT) analysis. If the model is used not as a theoretical formulation but as an analytic tool it becomes particularly appropriate to the analysis of input order effects.

This study analyzed the effects of constant and variable input orders in subjective organization using the ITOV measure, and retention forgetting using the TTT model. Results of two experiments, the second a replication with the substitution of a different list of items, provided strong evidence that constant-order lists are more easily organized and recalled than variable-order lists. ITOV was significantly higher for constant input lists and correlated substantially with recall. Variable-order lists showed more forgetting while the constant input lists produced greater retention.

The clear-cut results provide further evidence that the ITOV statistic is a good measure of subjective organization. Additionally, the Tulving TTT model was shown to be a powerful data-analytic tool in the study of free-recall verbal learning.