Cognitive aging: is there a dark side to environmental support?

Abstract

It has been known for some time that memory deficits among older adults increase when self-initiated processing is required and decrease when the environment provides task-appropriate cues. We propose that this observation is not confined to memory but can be subsumed under a more general developmental trend. In perception, learning or memory, and action management, older adults often rely more on external information than younger adults do, probably both as a direct reflection and indirect adaptation to difficulties in internally triggering and maintaining cognitive representations. This age-graded shift from internal towards environmental control is often associated with compromised performance. Cognitive aging research and the design of aging-friendly environments can benefit from paying closer attention to the developmental dynamics and implications of this shift.

Keywords: cognitive aging; cognitive control; environmental support; self-initiated processing.

Figure 1. Adult age differences in oscillatory stimulus entrainment during auditory oddball performance

Younger and older adults listened to a series of auditory stimuli consisting of a frequent and a rare, deviant tone (the “oddball”). The phase locking index (PLI, [76]) and evoked power (EP) were used to quantify the extent to which perceptual processing was entrained by the stimulus. The heatmaps display grand average stimulus-locked time-frequency maps for PLI and EP under the central electrode Cz when attending to the deviant stimulus. In each heatmap, a vertical line marks the stimulus onset, and rectangles mark the time-frequency ranges used to compute average PLI or EP values. Yellow rectangles with a plus sign indicate statistically significant positive correlations, and blue rectangles with a minus sign indicate statistically significant negative correlations with Identical Pictures (IP), an independently assessed test of perceptual speed. Scatterplots illustrating select correlations are shown below each heatmap. In younger adults (YA), greater phase locking and higher EP are positively related to perceptual speed. In older adults (OA), greater phase locking and higher EP are negatively related to perceptual speed. The data suggest that the early representation of auditory sensory events in old age occurs in a highly stimulus-driven manner that is less easily modulated by top-down influences. This interpretation is strengthened by additional data (not shown here) indicating that the amount of stimulus-induced synchronization as assessed by PLI and EP varies less a function of stimulus type (deviant versus standard) and instruction in older adults than in younger adults. Adapted from Müller et al. [6] and reprinted with permission.

Figure 2. Adult age differences in auditory attentional control

Participants were presented dichotic pairs of voiced versus unvoiced syllables (e.g., /ba/ versus /pa/), and were asked to report the syllable they hear. Perceptual saliency, shown on the X-axis, was manipulated by decreasing the intensity of either the right- or the left-ear input in 5-dB steps until a maximum difference of 20 dB between ears was reached. Negative values represent conditions in which left-ear stimuli were louder than right-ear stimuli, and positive values represent conditions in which right-ear stimuli were louder than left-ear stimuli. Attentional focus was manipulated by instructing participants to focus on the right ear, on the left ear, or on both ears (neutral focus). Reports are quantified by the laterality index, shown on the Y-axis, which expresses the amount of right-ear reports in relation to left-ear reports (i.e., [(right ear − left ear) / (right ear + left ear)] × 100). The laterality index ranges from −100% to +100%, with positive values indicating a right-ear advantage, and negative values indicating a left-ear advantage. When the stimulus of the attended ear is louder, then attention is facilitated by saliency; when the stimulus of the attended ear is softer, then the saliency advantage of the stimuli presented to the unattended ear has to be overcome by top-down attentional control. In contrast to younger adults (Panel A), who were capable of flexibly focusing their attention on auditory inputs from either the right or left ear, performance in older adults was driven almost exclusively by perceptual saliency (see Panel B). In particular, the distance between the data highlighted in red and the data point from the neutral-focus condition underscore younger adults’ ability to use top-down modulation to overcome conflicts between perceptual saliency and attentional focus; the overlap between the corresponding conditions among older adults indicates that this ability is severely impaired in old age. Figure adapted from Passow et al. [7] with permission.

Figure 3

Two ways in which reliance on actively maintained representations and external support may change from early to late adulthood. Direct link: Reliance on external support is inversely linked to the robustness of top-down, internally maintained representations. Indirect link: Reliance on external support also depends on strategic adaptations to attenuate the adverse consequences of less robust internal representations. Hence the same amount of decline in top-down control can lead to different developmental trajectories of environmental support across individuals, and within individuals across different domains.

Figure Box 1

A hypothetical rank order of the relative importance of environmental support and self-initiated processing for different experimental paradigms of learning and memory. The figure is adapted from Craik [1]. The numbers to the right of the figure are based on a meta-analysis by La Voie and Light [61]. They show the effect size estimates of the performance advantage of younger adults over older adults. The data follow the hypothesized order [62]. Adapted from Craik [1] with permission.

Figure Box 2

Panel A. The fade-out paradigm. Panel B. Results from Spieler et al. [50]. Reprinted with permission.