Proactive Interference and Memory Updating in Older Adults: A Life-Span Perspective

Abstract

Proactive interference (PI) from previously learned information impairs recall of new material, yet little is known about developmental changes in PI resolution. We administered a modified A-B, A-D paradigm to younger (n=28, M=22 years) and older adults (n=35, M=71 years) to examine list-learning interference under varying retention intervals. Results showed older adults exhibited significantly greater PI buildup over learning trials (p < .01), with diminished recovery after a 1-hour delay. Implications for understanding memory deficits in aging are discussed.

Introduction

Proactive interference (PI) has long been recognized as a fundamental constraint on human learning and memory, yet individual differences in the ability to suppress prepotent information remain incompletely understood. Classical A-B, A-D paradigms have shown that when participants learn a first list (A-B) and are subsequently exposed to a second list with overlapping cue terms but new responses (A-D), the prior association interferes with acquisition of the new material. This phenomenon is particularly pronounced in older adults, who show reduced ability to inhibit or overcome previously established responses across multiple cognitive domains.

The present study extends prior developmental research on PI resolution by examining performance across the adult life span in a controlled laboratory setting. We hypothesized that age-related deficits in executive control would manifest as exaggerated interference effects and prolonged recovery periods following learning trials. Understanding these mechanisms is critical for characterizing normative cognitive aging and for developing effective training protocols to enhance memory performance in populations at risk for age-related decline.

Method

Participants

Twenty-eight younger adults (age range 18-30 years, M=22.1 years, SD=3.8) and thirty-five older adults (age range 65-82 years, M=71.4 years, SD=5.2) participated in the study. Participants were recruited from the Ottawa community via local senior centers and university posting boards. All participants reported normal or corrected-to-normal vision and hearing, and screened negative on a brief cognitive status interview. Younger and older groups did not differ on years of education, t(61)=0.87, p > .05.

Procedure

Participants completed a computerized version of the A-B, A-D list-learning task using PsyScope stimulus presentation software on a Macintosh computer. The experiment consisted of two phases. In the first phase (A-B learning), participants studied eight cue-target pairs (e.g., LAKE-CABIN) presented once per trial over four learning trials, with stimuli displayed for 3 seconds each followed by a 2-second blank interval. In the second phase (A-D learning), the same cues were paired with new targets (e.g., LAKE-FOREST) over four learning trials using identical timing parameters. Immediately following A-D learning (0-minute delay) and again after a 1-hour retention interval, participants were cued with the original A cue terms and asked to freely recall the target. Responses were recorded on paper response forms by the experimenter and later coded for accuracy.

Results

Cumulative recall on the final trial of A-B learning showed no significant differences between age groups (younger: M=7.2 items, SD=0.9; older: M=6.9 items, SD=1.1), t(61)=1.15, p > .05. However, performance diverged substantially during A-D learning. A 2 (Age Group) x 4 (Learning Trial) mixed analysis of variance on A-D correct responses revealed significant main effects of Age Group, F(1, 61)=8.34, p < .01, and Learning Trial, F(3, 183)=42.18, p < .001, and a significant Age x Trial interaction, F(3, 183)=3.21, p < .05. Older adults recalled fewer correct A-D pairs on each learning trial compared to younger adults, with the largest differences evident on early trials (Trial 1: younger M=2.1, older M=1.3; Trial 4: younger M=5.8, older M=4.6).

On the immediate recall test (0-minute delay), younger adults recalled M=6.1 (SD=1.2) A-D pairs compared to older adults' M=4.7 (SD=1.4), t(61)=4.32, p < .001. After the 1-hour retention interval, younger adults showed minimal loss (M=5.9, SD=1.3), whereas older adults demonstrated significantly greater forgetting (M=3.4, SD=1.8), t(61)=5.87, p < .001. Intrusion errors (erroneous recall of A-B pairs during A-D testing) were analyzed separately; older adults produced more A-B intrusions at both the immediate test (younger: M=0.6, older: M=1.8, t(61)=3.12, p < .01) and delayed test (younger: M=0.5, older: M=2.3, t(61)=4.01, p < .001), suggesting greater difficulty inhibiting the previously learned association.

Discussion

The present findings demonstrate age-related increases in susceptibility to proactive interference, consistent with recent theoretical accounts emphasizing deficits in inhibitory control as a core feature of cognitive aging. Older adults acquired the new (A-D) associations more slowly, retained fewer correct responses across retention intervals, and produced substantially more intrusion errors reflecting persisting activation of the competing prior response. These results extend earlier cross-sectional findings and suggest that the ability to suppress prepotent but task-irrelevant information declines substantially in the later adult years.

The pronounced deficits observed after the 1-hour delay interval are particularly noteworthy, as they suggest age differences in consolidation of new learning or in the maintenance of retrieval-relevant context over time. Future research utilizing neuroimaging methods (e.g., fMRI) to examine neural activity during PI resolution may clarify the neural substrates of these behavioral deficits. Additionally, longitudinal studies tracking PI performance across multiple occasions would help distinguish between true age changes and cohort effects in this population.

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