Item analyses of memory differences

Abstract

Objective: Although performance on memory and other cognitive tests is usually assessed with a score aggregated across multiple items, potentially valuable information is also available at the level of individual items.

Method: The current study illustrates how analyses of variance with item as one of the factors, and memorability analyses in which item accuracy in one group is plotted as a function of item accuracy in another group, can provide a more detailed characterization of the nature of group differences in memory. Data are reported for two memory tasks, word recall and story memory, across age, ability, repetition, delay, and longitudinal contrasts.

Results: The item-level analyses revealed evidence for largely uniform differences across items in the age, ability, and longitudinal contrasts, but differential patterns across items in the repetition contrast, and unsystematic item relations in the delay contrast.

Conclusion: Analyses at the level of individual items have the potential to indicate the manner by which group differences in the aggregate test score are achieved.

Keywords: Group differences; Group-by-item interactions; Memorability analysis; Score decomposition; Systematic relations.

Figure 1

Schematic illustration of possible outcomes from memorability analyses. Each point represents the hypothetical accuracy for an individual item averaged across participants. The X axis corresponds to performance in one group (or condition), and the Y axis correspond to performance in another group (or condition).

Figure 2

Serial position functions for word recall (top left) and logical memory (bottom left), and memorability functions for word recall (top right) and logical memory (bottom right) for the age contrast.

Figure 3

Serial position functions for word recall (top left) and logical memory (bottom left), and memorability functions for word recall (top right) and logical memory (bottom right) for the ability contrast.

Figure 4

Serial position functions for word recall (top left) and logical memory (bottom left), and memorability functions for word recall (top right) and logical memory (bottom right) for the repetition contrast.

Figure 5

Serial position functions for word recall (top left) and logical memory (bottom left), and memorability functions for word recall (top right) and logical memory (bottom right) for the delay contrast.

Figure 6

Serial position functions for word recall (top left) and logical memory (bottom left), and memorability functions for word recall (top right) and logical memory (bottom right) for the longitudinal contrast.