Older Adults' Lure Discrimination Difficulties on the Mnemonic Similarity Test are Significantly Correlated with their Visual Perception.

Objectives: Pattern separation in memory encoding entails creating and storing distinct, detailed representations to facilitate storage and retrieval. The Mnemonic Similarity Task (MST; Stark, S. M., Yassa, M. A., Lacy, J. W., & Stark, C. E. [2013]. A task to assess behavioral pattern separation [BPS] in humans: Data from healthy aging and mild cognitive impairment. Neuropsychologia, 51, 2442-2449) has been used to argue that normal aging leads to pattern separation decline. We sought to replicate previous reports of age-related difficulty on this behavioral pattern separation estimate and to examine its neuropsychological correlates, specifically long-term memory function, executive function, and visual perception. Methods: We administered an object version of the MST to 31 young adults and 38 older adults. It involved a single-probe recognition memory test in which some of the originally studied objects had been replaced with perceptually similar lures, and participants had to identify each as old, a lure, or new. Results: Despite their corrected item recognition scores being superior to those of the young adults, the older adults had significantly greater difficulty than the young in discriminating the similar-looking lures from the original items. Interestingly, this lure discrimination difficulty was significantly correlated with visual perception rather than with long-term memory or executive function. Discussion: These results suggest that although adult age differences on the MST are reliable, care should be taken to separate perceptual from memory discrimination difficulties as the reason.