Incidental Learning: A Systematic Review of Its Effect on Episodic Memory Performance in Older Age

Abstract

Episodic memory is the capacity to encode, store, and retrieve information of specific past events. Several studies have shown that the decline in episodic memory accompanies aging, but most of these studies assessed memory performance through intentional learning. In this approach, the individuals deliberately acquire knowledge. Yet, another method to evaluate episodic memory performance–receiving less attention by the research community–is incidental learning. Here, participants do not explicitly intent to learn. Incidental learning becomes increasingly important over the lifespan, since people spend less time in institutions where intentional learning is required (e.g., school, university, or at work). Yet, we know little how incidental learning impacts episodic memory performance in advanced age. Likewise, the neural mechanisms underlying incidental learning in older age remain largely unknown. Thus, the immediate goal of this review was to summarize the existing literature on how incidental learning changes with age and how neural mechanisms map onto these age-related changes. We considered behavioral as well as neuroimaging studies using incidental learning paradigms (alone or in combination with intentional learning) to assess episodic memory performance in elderly adults. We conducted a systematic literature search on the Medline/PubMed, Cochrane, and OVID SP databases and searched the reference lists of articles. The search yielded 245 studies, of which 34 concerned incidental learning and episodic memory in older adults. In sum, these studies suggest that aging particularly affects episodic memory after incidental learning for cognitively demanding tasks. Monitoring deficits in older adults might account for these findings since cognitively demanding tasks need increased attentional resources. On a neuronal level, dysregulation of the default-mode-network mirrors monitoring deficits, with an attempt to compensate through increased frontal activity. Future (neuroimaging) studies should systematically evaluate retrieval tasks with diverging cognitive load and consider the influence of attention and executive functions in more detail.

Older Adults Encode Task-Irrelevant Stimuli, but Can This Side-Effect be Useful to Them?

“…An important difference between Biss’s experiment and ours was that their participants first intentionally studied and recalled the words or names, developing semantic codes, and in the later phase this representation was consolidated by incidental rehearsal; maintenance rehearsal primed the existing representations. Other studies applying incidental learning direct attention to the later to-be-retrieved stimuli using tasks appropriate for deep (i.e., semantic) or shallow (i.e., perceptual) encoding (Wagnon et al, 2019 ), e.g., orientation judgment (upright/inverted) of face stimuli as shallow, and occupation judgment (actor/politician) as a deep incidental encoding of the faces (Marzi and Viggiano, 2010 ). However, in our case participants had no task at all with the stimuli they should have recognized later, there were no intention and motivation to learn these stimuli, there was no need for the deeper encoding of them, thus they did not have an initial representation that they could retain by stimulus repetition, and consolidate the memory trace.…”

The Functional Foundations of Episodic Memory Remain Stable Throughout the Lifespan

“…Similarly, the results may partially depend on the incidental/intentional nature of the encoding task and the availability of prior knowledge of the different age groups ( Schneider et al. 1993 ; Wagnon et al. 2019 ) as it can modulate the lifespan trajectories of cognition and neural recruitment for certain regions (i.e., frontoparietal attentional networks) ( Maril et al.…”

Cognitive and contextual factors modulating grammar learning at older ages

“…This pattern also suggests that older adults are less effective than younger adults in their use of explicit strategies, but that implicit strategies might be efficiently used by the older adults since learning differences with the younger adults where not evident in conditions where these strategies were required (implicit complex conditions) and used ( Midford and Kirsner, 2005 ). More recent data also indicate that older adults seem to relay more on incidental than intentional learning strategies (see Wagnon et al, 2019 for a review). Since older adults have a notable decay in declarative memory, the differences between younger and older adults in language learning might also be related to the cognitive resources available to the participants, so that age related impairments in cognitive resources might reduce the efficacy of intentional strategies in explicit/intentional learning conditions ( Ingvalson et al, 2017 ).…”