Associative memory in aging: the effect of unitization on source memory

Abstract

In normal aging, memory for associations declines more than memory for individual items. Unitization is an encoding process defined by creation of a new single entity to represent a new arbitrary association. The current study tested the hypothesis that age-related differences in associative memory can be reduced by encoding instructions that promote unitization. In two experiments, groups of 20 young and 20 older participants learned new associations between a word and a background color under two conditions. In the item detail condition, they had to imagine that the item is the same color as the background-an instruction promoting unitization of the associations. In the context detail condition, which did not promote unitization, they had to imagine that the item interacted with another colored object. At test, they had to retrieve the color that was associated with each word (source memory). In both experiments, the results showed an age-related decrement in source memory performance in the context detail but not in the item detail condition. Moreover, Experiment 2 examined receiver operating characteristics in older participants and indicated that familiarity contributed more to source memory performance in the item detail than in the context detail condition. These findings suggest that unitization of new associations can overcome the associative memory deficit observed in aging, at least for item-color associations.

Figure 1

Experiment 1. Proportions of correct source judgments as a function of group and condition. A. Global performance. B. Performance assessed separately for easy-to-imagine and difficult-to-imagine associations.

Figure 2

Experiment 2. Proportions of correct source judgments as a function of group and condition. A. Global performance. B. Performance assessed separately for easy-to-imagine and difficult-to-imagine associations.

Figure 3

A. Older adults’ average ROC curves for the item detail and context detail conditions, fit using the Dual-Process Signal Detection Model (DPSD model). B. Recollection (proportion) and familiarity (d’) estimates based on DPSD model fits as a function of condition.