M. Karl Healey

Chapter 22 Cognitive aging and increased distractibility: Costs and potential benefits

Older adults show a characteristic pattern of impaired and spared functioning relative to younger adults. Elsewhere we have argued that many age-related changes in cognitive function are rooted in an impaired ability to inhibit irrelevant information and inappropriate responses. In this chapter we review evidence that as a direct result of impaired inhibitory processes, older adults tend to be highly susceptible to distraction. We suggest that because the distinction between relevant and irrelevant is seldom either clear or static, distractibility can manifest as either a cost or a benefit depending on the situation. We review evidence that in situations in which it interferes with the current task, distraction is disproportionately detrimental to older adults compared to university aged adults, but that when previously distracting information becomes relevant, older adults show a benefit whereas younger adults do not.

Direct Evidence for the Role of Inhibition in Resolving Interference in Memory

Interference from competing material at retrieval is a major cause of memory failure. We tested the hypothesis that such interference can be overcome by suppressing competing responses. In a three-phase task, participants in the critical interference condition first performed a vowel-counting task (Phase 1) that included pairs of orthographically similar words (e.g., allergy and analogy). After a delay, participants were asked to solve word fragments (e.g., a _ l _ _ gy) that resembled both words in a pair they had seen, but could be completed only by one of these words (Phase 2). We then measured the consequence of having successfully resolved interference in Phase 2 by asking participants to read a list of words, including rejected competitor words (i.e., the word in each pair that could not be used to solve the word fragments), as quickly as possible (Phase 3). Participants in the interference condition were slower to name the competitor words than participants in conditions that did not require interference resolution. These results constitute direct evidence for the role of active suppression in resolving interference during memory retrieval.

Theta and High-Frequency Activity Mark Spontaneous Recall of Episodic Memories

Humans possess the remarkable ability to search their memory, allowing specific past episodes to be re-experienced spontaneously. Here, we administered a free recall test to 114 neurosurgical patients and used intracranial theta and high-frequency activity (HFA) to identify the spatiotemporal pattern of neural activity underlying spontaneous episodic retrieval. We found that retrieval evolved in three electrophysiological stages composed of: (1) early theta oscillations in the right temporal cortex, (2) increased HFA in the left hemisphere including the medial temporal lobe (MTL), left inferior frontal gyrus, as well as the ventrolateral temporal cortex, and (3) motor/language activation during vocalization of the retrieved item. Of these responses, increased HFA in the left MTL predicted recall performance. These results suggest that spontaneous recall of verbal episodic memories involves a spatiotemporal pattern of spectral changes across the brain; however, high-frequency activity in the left MTL represents a final common pathway of episodic retrieval.

The role of attention during retrieval in working-memory span: A dual-task study

We tested the hypothesis that retrieving target words in operation span (OSpan) involves attention-demanding processes. Participants completed the standard OSpan task and a modified version in which all equations preceded all target words. Recall took place under either full attention or easy versus hard divided-attention conditions. Recall suffered under divided attention with the recall decrement being greater for the hard secondary task. Moreover, secondary-task performance was disrupted more by the standard OSpan task than by the modified version with the hard secondary task showing the larger decrement. Finally, the time taken to start recalling the first word was considerably longer for the standard version than for the modified version. These results are consistent with the proposal that successful OSpan task performance in part involves the attention-demanding retrieval of targets from long-term memory.

The Stability of Working Memory: Do Previous Tasks Influence Complex Span?.

Schmeichel (2007) reported that performing an initial task before completing a working memory span task can lower span scores and suggested that the effect was due to depleted cognitive resources. We showed that the detrimental effect of prior tasks depends on a match between the stimuli used in the span task and the preceding task. A task requiring participants to ignore words reduced performance on a subsequent word-based verbal span task but not on an arrow-based spatial span task. Ignoring arrows had the opposite pattern of effects: reducing performance on the spatial span task but not on the word-based span task. Finally, we showed that antisaccade, a nonverbal task that taxes domain-general processes implicated in working memory, did not influence subsequent performance of either a verbal or a spatial span task. Together these results suggest that while span is sensitive to prior tasks, that sensitivity does not stem from depleted resources. (PsycINFO Database Record (c) 2011 APA, all rights reserved).

A four-component model of age-related memory change

We develop a novel, computationally explicit, theory of age-related memory change within the framework of the context maintenance and retrieval (CMR2) model of memory search. We introduce a set of benchmark findings from the free recall and recognition tasks that include aspects of memory performance that show both age-related stability and decline. We test aging theories by lesioning the corresponding mechanisms in a model fit to younger adult free recall data. When effects are considered in isolation, many theories provide an adequate account, but when all effects are considered simultaneously, the existing theories fail. We develop a novel theory by fitting the full model (i.e., allowing all parameters to vary) to individual participants and comparing the distributions of parameter values for older and younger adults. This theory implicates 4 components: (a) the ability to sustain attention across an encoding episode, (b) the ability to retrieve contextual representations for use as retrieval cues, (c) the ability to monitor retrievals and reject intrusions, and (d) the level of noise in retrieval competitions. We extend CMR2 to simulate a recognition memory task using the same mechanisms the free recall model uses to reject intrusions. Without fitting any additional parameters, the 4-component theory that accounts for age differences in free recall predicts the magnitude of age differences in recognition memory accuracy. Confirming a prediction of the model, free recall intrusion rates correlate positively with recognition false alarm rates. Thus, we provide a 4-component theory of a complex pattern of age differences across 2 key laboratory tasks.

Below-Baseline Suppression of Competitors During Interference Resolution by Younger but Not Older Adults:

Resolving interference from competing memories is a critical factor in efficient memory retrieval, and several accounts of cognitive aging suggest that difficulty resolving interference may underlie memory deficits such as those seen in the elderly. Although many researchers have suggested that the ability to suppress competitors is a key factor in resolving interference, the evidence supporting this claim has been the subject of debate. Here, we present a new paradigm and results demonstrating that for younger adults, a single retrieval attempt is sufficient to suppress competitors to below-baseline levels of accessibility even though the competitors are never explicitly presented. The extent to which individual younger adults suppressed competitors predicted their performance on a memory span task. In a second experiment, older adults showed no evidence of suppression, which supports the theory that older adults’ memory deficits are related to impaired suppression.

Is memory search governed by universal principles or idiosyncratic strategies

Laboratory paradigms have provided an empirical foundation for much of psychological science. Some have argued, however, that such paradigms are highly susceptible to idiosyncratic strategies and that many findings do not reflect fundamental cognitive principles but are instead artifacts of averaging across participants who employ different strategies. We developed a set of techniques to rigorously test the extent to which average data are distorted by such strategy differences and applied these techniques to free recall data from the Penn Electrophysiology of Encoding and Retrieval Study. Recall initiation showed evidence of subgroups: The majority of participants initiated recall from the last item in the list, but one subgroup showed elevated initiation probabilities for items 2 to 4 positions back from the end of the list, and another showed elevated probabilities for the beginning of the list. By contrast, serial position curves and temporal and semantic clustering functions were remarkably consistent, with almost every participant exhibiting a recognizable version of the average function, suggesting that these functions reflect fundamental principles of the memory system. The approach taken here can serve as a model for evaluating the extent to which other laboratory paradigms are influenced by individual differences in strategy use.

Individual differences in memory search and their relation to intelligence.

Attempts to understand why memory predicts intelligence have not fully leveraged state-of-the-art measures of recall dynamics. Using data from a multisession free recall study, we examine individual differences in measures of recall initiation and postinitiation transitions. We identify 4 sources of variation: a recency factor reflecting variation in the tendency to initiate recall from an item near the end of the list, a primacy factor reflecting a tendency to initiate from the beginning of the list, a temporal factor corresponding to transitions mediated by temporal associations, and a semantic factor corresponding to semantically mediated transitions. Together, these 4 factors account for 83% of the variability in overall recall accuracy, suggesting they provide a nearly complete picture of recall dynamics. We also show that these sources of variability account for over 80% of the variance shared between memory and intelligence. The temporal association factor was the most influential in predicting both recall accuracy and intelligence. We outline a theory of how controlled drift of temporal context may be critical across a range of cognitive activities.