Effect of Encoding Condition on Source Memory for Odors in Healthy Young and Older Adults

Abstract

Background: Source memory has been shown to be more affected by aging than item memory. Aging also has been shown to result in impairments in odor memory. Objective: The aim of the study is to examine the effects of explicit encoding instructions on source memory for olfactory stimuli in healthy older and young adults. Methods: Source and item memory for odors were assessed in two conditions. In the uninformed condition, young (18–30) and older adults (65+) were presented with 16 odors by two sources (male and female) without instruction at encoding and no warning of a subsequent memory task. In the informed condition, young and older adults were instructed to encode the stimuli and their respective sources. To assess item memory, the participant was presented with an odor from the task and a new odor and was asked to indicate which odor had been presented previously. On source memory trials, the participant was presented with an odor from the task and was asked to indicate whether the male or female presented the odor. Results: A 2 × 2 × 2 analysis of variance revealed that older adults were significantly impaired relative to young adults on the source memory trials in both the uninformed and informed conditions, F(1, 52) = 18.15, p < 0.001. However, older adults matched the performance of young adults on item memory trials, regardless of encoding condition. Conclusions: Even with conscious effort to encode the sources associated with the odors, older adults show significant source memory impairments. The mnemonic processes used to integrate contextual source information with item memory during encoding may fail to initiate due to the amount of effort required to encode the olfactory stimulus. The difficulty of encoding and subsequently retrieving the source may be increased due to the difficulty of encoding the odors. The results demonstrate the robust effects of aging on source memory for odors.