Although executive functions can be improved by training, little is known about the extent to which these training-related benefits can be transferred to other tasks, or whether this transfer can be modulated by the type of training. This study investigated lifespan changes in near transfer of task-switching training to structurally similar tasks and its modulation by verbal self-instructions and variable training, as well as far transfer to structurally dissimilar 'executive' tasks and fluid intelligence. Three age groups (8-10; 18-26; 62-76 years of age) were examined in a pretest-training-posttest design. We found near transfer of task-switching training in all age groups, especially in children and older adults. Near transfer was enhanced in adults and impaired in children when training tasks were variable. We also found substantial far transfer to other executive tasks and fluid intelligence in all age groups, pointing to the transfer of relatively general executive control abilities after training.

Age differences in 2 components of task-set switching speed were investigated in 118 adults aged 20 to 80 years using task-set homogeneous (e.g., AAAA... ) and task-set heterogeneous (e.g., AABBAABB... ) blocks. General switch costs were defined as latency differences between heterogeneous and homogeneous blocks, whereas specific switch costs were defined as differences between switch and nonswitch trials within heterogeneous blocks. Both types of costs generalized over verbal, figural, and numeric stimulus materials; were more highly correlated to fluid than to crystallized abilities; and were not eliminated after 6 sessions of practice, indicating that they reflect basic and domain-general aspects of cognitive control. Most important, age-associated increments in costs were significantly greater for general than for specific switch costs, suggesting that the ability to efficiently maintain and coordinate 2 alternating task sets in working memory instead of 1 is more negatively affected by advancing age than the ability to execute the task switch itself.

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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.

The human mediofrontal cortex, especially the anterior cingulate cortex, is commonly assumed to contribute to higher cognitive functions like performance monitoring. How exactly this is achieved is currently the subject of lively debate but there is evidence that an event's valence and its expectancy play important roles. One prominent theory, the reinforcement learning theory by Holroyd and colleagues (2002, 2008), assigns a special role to feedback valence, while the prediction of response-outcome (PRO) model by Alexander and Brown (2010, 2011) claims that the mediofrontal cortex is sensitive to unexpected events regardless of their valence. However, paradigms examining this issue have included confounds that fail to separate valence and expectancy.In the present study, we tested the two competing theories of performance monitoring by using an experimental task that separates valence and unexpectedness of performance feedback. The feedback-related negativity of the event-related potential, which is commonly assumed to be a reflection of mediofrontal cortex activity, was elicited not only by unexpected negative feedback, but also by unexpected positive feedback. This implies that the mediofrontal cortex is sensitive to the unexpectedness of events in general rather than their valence and by this supports the PRO model.

This study examined developmental differences in the ERP correlates of internal and external error processing (ERN and FRN) during learning. A probabilistic learning task was applied in which feedback validity was manipulated. The behavioral data showed similar accuracy for children and adults when feedback was valid, whereas age differences were obtained when it was partially invalid. We found no reduction of the ERN for children compared to adults when performance levels were equated. Yet, contrary to adults, children did not differentiate between responses when feedback was partially invalid, indicating that they are less able to represent the correctness of a response when there is interference during learning. Moreover, we found a larger FRN and reduced ERP learning effects for positive feedback for children, suggesting that they are more sensitive to external error feedback and less able to disengage from positive feedback during learning.

Age-related changes in executive functioning across the lifespan were assessed in children (mean age ¼ 9.4 years), younger adults (mean age ¼ 21.5 years), and older adults (mean age ¼ 65.3 years). Executive functioning was investigated with a task-switching paradigm that permits the separation of two control components: to select and to switch between task sets. The specific aims of this study were (a) to determine developmental functions in both control components across the lifespan; and (b) to examine whether age-related changes in these components are influenced by verbal prompts during task preparation. The results revealed an inverted u-shaped developmental function for the ability to select between task sets but not for the ability to switch between task sets. In contrast to younger adults and children, older adults generally benefited from verbalizations during task preparation. Children, but not older adults, showed a facilitation of task execution when verbal prompts were task-compatible. Conversely, older adults, but not children, showed stronger interference when verbal prompts are task-incompatible. Our findings suggest that inner speech in an important modulator of developmental changes in executive functioning across the lifespan.

The present study examined age differences in executive functioning, using an externally cued task-switching paradigm. Two components of task switching were assessed: the ability to maintain and select among task sets (general switch costs) and the ability to switch between task sets (specific switch costs). In contrast to previous findings, we found large age-related differences in specific switch costs, especially when the number of potentially relevant task sets is increased from two to four. Age-related differences in general switch costs were absent when external task cues subserved executive processing in task switching. Generally, the findings suggest that age-related impairments in task-switching components vary as a function of task uncertainty, such as the presence of environmental prompts to behavior. © 2002 Elsevier Science (USA)