Age Differences in the Transfer and Maintenance of Practice-Induced Improvements in Task Switching: The Impact of Working-Memory and Inhibition Demands

Abstract

Recent aging studies on training in task switching found that older adults showed larger improvements to an untrained switching task as younger adults do. However, less clear is what type of cognitive control processes can explain these training gains as participants were trained with a particular type of switching task including bivalent stimuli, requiring high inhibition demands, and no task cues helping them keeping track of the task sequence, and by this, requiring high working-memory (WM) demands. The aims of this study were first to specify whether inhibition, WM, or switching demands are critical for the occurrence of transfer and whether this transfer depends on the degree of overlap between training and transfer situation; and second to assess whether practiced-induced gains in task switching can be maintained over a longer period of time. To this end, we created five training conditions that varied in switching (switching vs. single task training), inhibition (switching training with bivalent or univalent stimuli), and WM demands (switching training with or without task cues). We investigated 81 younger adults and 82 older adults with a pretest-training-posttest design and a follow-up measurement after 6 months. Results indicated that all training and age groups showed improvements in task switching and a differential effect of training condition on improvements to an untrained switching task in younger and older adults. For younger adults, we found larger improvements in task switching for the switching groups than the single-task training group independently of inhibition and WM demands, suggesting that practice in switching is most critical. However, these benefits disappeared after 6 months. In contrast, for older adults training groups practicing task switching under high inhibition demands showed larger improvements to untrained switching tasks than the other groups. Moreover, these benefits were maintained over time. We also found that the transfer of benefits in task switching was larger with greater overlap between training and transfer situation. However, results revealed no evidence for transfer to other untrained cognitive task. Overall, the findings suggest that training in resolving interference while switching between two tasks is most critical for the occurrence of transfer in the elderly.

Keywords: aging; inhibition; task-switching training; transfer; working memory.

FIGURE 1

Illustration of the trial procedure, task cues, and stimuli in the four training sessions for the four task-switching training groups. Participants had to switch between a digit task (odd or even?) and a letter task (consonant or vowel?). Task-switching Training Group 1 received task cues and practiced with univalent stimuli (Upper/left). Task-switching Training Group 2 also received task cues and practiced with bivalent stimuli (Lower/left). Task-switching Training Group 3 practiced without task cues and with univalent stimuli (Upper/right). Task-switching Training Group 4 practiced without task cues and with bivalent stimuli (Lower/right).

FIGURE 2

Switching costs (in ms) as a function of session and task-switching training group separately for younger adults (Left) and older adults (Right).

FIGURE 3

Reduction of mixing costs from pretest to posttest to follow up (A) for younger adults and (B) for older adults.

FIGURE 4

Reduction of mixing costs from pretest to posttest separately for younger adults (left) and for older adults (right) as a function of overlap between the training and transfer condition for the Task-switching Group 1 (A) Group 2 (B) Group 3 (C) and Group 4 (D).