Associative symmetry and memory theory.

This article reexamines the theory and data concerning two opposing views of episodic association. The independent association hypothesis (IAH) sees associations as unidirectional and separately modifiable links between individual item representations. The associative symmetry hypothesis (ASH) sees an association as a holistic conjunction of the constituent items, blending the elements of their representations into a new one. In early tests of these hypotheses, experimenters compared forward and backward recall of paired associates, looking for asymmetries. Although some studies showed significant differences between forward and backward recall, the vast majority did not. The author of this study used a mathematical analysis of distributed memory models to reexamine this classic question. These analyses revealed that symmetric and asymmetric models can mimic each other, offering identical predictions regarding forward and backward recall. To distinguish these models, the author examined the correlation between forward and backward recall at the level of individual pairs of items. Both this correlation and the correlation between recall of pairs tested in the same direction were near unity. These results provide new evidence favoring the ASH over the IAH.