Verbal self-instructions in task switching: a compensatory tool for action-control deficits in childhood and old age?

Authors


  • 1

    Both psychometric tests were administered in a separate session prior to the experiment.

  • 2

    An adapted version of the Wechsler Digit-Symbol Substitution Test was used to assess perceptual speed of processing (Wechsler, 1982). The template contained nine digit-symbol mappings. All participants were instructed to fill in the symbol corresponding to the digit. The score refers to the number of correct symbols after 90 s.

  • 3

    In the knowledge test, 35 items are presented successively on the screen. Each item included one correct word and four non-words. The participants are asked to find the one correct word. The score was the number of correct words.

  • 4

    In German: Goldfisch, Hai, Wal, Schildkröte, Frosch, Seelöwe, Nilpferd, Krebs, Seestern, Eule, Käfer, Fliege, Storch, Taube, Tagpfauenauge, Singvogel, Zitronenfalter, Wellensittich.

  • 5

    If subjects made on average more than two errors per block (2/16 = 12.5%) in the second half of the first session, it was relatively likely that they would still have problems maintaining the task sequence in mixing blocks. Therefore, they received more practice. This was the case for eight younger children, two older children, and six older adults. Given that children and older adults received more practice than younger adults, this could have reduced age-related differences in task switching (thereby working against our expectation of finding age differences in task switching). Importantly, excluding these subjects from all overall analyses did not change any significant finding of the present study.

  • 6

    The time interval between the introduction phase and the experimental phase was on average 6 days (5 days for the younger children; 7.2 days for older children; 5.5 days for younger adults, and 5.1 days for older adults). Practice sessions in the experimental phase were held once a week.

  • 7

    Three sequences of verbalization conditions were used: (1) control – relevant – irrelevant; (2) relevant – irrelevant – control; (3) irrelevant – control – relevant. Each subject started with a different sequence condition in each of the three sessions. Within each session the sequence of the verbalization condition was counterbalanced across subjects.

  • 8

    When subjects did not reach the performance criteria in the first session, we used data from the second session. Practice data of one subject were lost during data collection.

  • 9

    To rule out possible speed–accuracy trade-offs for the effects of verbalization benefits on mixing costs, we assigned subjects to two groups with low and high error rates. We conducted an ANOVA on latencies with the additional factor of error group (low, high). Importantly, we found no reliable interactions between verbalization benefits, mixing costs, and error group (p = .18), or error group and age (p = .33).

Address for correspondence: Jutta Kray, Department of Psychology, Saarland University, P.O. Box 15 11 50, D-66041 Saarbrücken, Germany; e-mail: j.kray@mx.uni-saarland.de

Abstract

This study examined the influence of verbal self-instructions on age differences in task switching. Task-switching ability, measured as the difference between performance in single-task blocks and in mixed-task blocks in which participants switch between two tasks (mixing costs), increases during childhood and decreases in old age. To measure the influence of language on task switching, we compared conditions in which participants either (a) named the next task to be performed (i.e. task-relevant verbalization), (b) verbalized words not related to the task at hand (i.e. task-irrelevant verbalization), or (c) did not verbalize (control condition). Results indicated that mixing costs were substantially reduced under task-relevant verbalization and increased under task-irrelevant verbalization. Moreover, age-related differences in mixing costs were increased when the use of inner speech was disrupted and were reduced when participants performed task-relevant verbalization. These findings suggest that verbal self-instructions are a useful tool for retrieving the next task goal and for reducing action-control deficits in younger children and older adults.

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