Encoding and retrieval eye movements mediate age differences in pattern completion

Older adults often mistake new information as ‘old’, yet, the mechanisms underlying this response bias remain unclear. Typically, false alarms by older adults are thought to reflect pattern completion – the retrieval of a previously encoded stimulus in response to partial input. However, other work suggests that age-related retrieval errors can be accounted for by deficient encoding processes. In the present study, we used eye movement (EM) monitoring to quantify older adults’ pattern completion bias as a function of EMs during both encoding and partially cued retrieval. Analysis of EMs revealed reduced encoding-related differentiation (i.e., more similar EMs across encoded images) and increased retrieval-related reinstatement (i.e., more similar EMs across encoding and retrieval) by older relative to younger adults, with both encoding and retrieval EMs predicting false alarms. These findings indicate that age-related changes in both encoding and retrieval processes, indexed by EMs, underlie older adults’ increased vulnerability to memory errors.