Plasticity is a central concept within the life-span approach of development and is defined as the ability of an individual to change and reorganize in response to environmental challenges (e.g., Baltes & Singer, 20019. Such intraindividual changes can be induced by systematic cognitive training. Recent studies suggest that substantial amounts of plasticity can be induced in executive control functions with a process-based training approach. These newer studies show that repeated practice on executive control tasks not only improved performance on these trained tasks, but also led to improvements in nontrained tasks (i.e., transfer; e.g., Jaeggi, Buschkuehl, Jonides, & Perrig, 2008; Karbach & Kray, 2009). Executive control processes are especially relevant from a developmental perspective because executive control is involved in a wide range of complex cognitive activities (e.g., van der Sluis, de Jong, & van der Leij, 2007) and is one of the most central areas of cognitive development (e.g., Craik & Bialystok, 2006).
The current thesis aimed at elucidating several important questions concerning the plasticity of executive control functions induced by systematic cognitive training. Firstly, the amount, range, and stability of plasticity in adolescents and older adults were investigated. Secondly, studies explored if training design, age, and interindividual differences moderate the amount and range of plasticity. Furthermore, the current thesis aimed at exploring how process-based training specifically leads to transfer effects.
To explore these questions, all studies employed a pretest-posttest-design comparing a group of participants that was trained with a process-based training approach to a group of control partici-pants that did not receive the training. Pretraining and posttraining sessions incorporated systematic assessment of transfer measures in different cognitive domains. The first study set out to investigate if executive control can be trained in adolescents with a task switching training. Additionally, the study explored what particular domains of executive control may underlie training and transfer effects, and if acute bouts of exercise directly prior to cognitive training enhance training effects. Analyses indicated substantial training effects for both training groups (with or without acute exercise) and near transfer to a similar switching task. Other findings of transfer were limited to a speed task and a tendency for faster reaction times in an updating task. Thus, findings indicate, for the first time, that executive control can be enhanced in adolescents through a short training. Furthermore, analyses suggest that updating may be of particular relevance for the effects of the task switching training. Analyses revealed no additional effects of the exercise intervention.
The second study set out to explore, for the first time, the effects of a process-based training ap-proach in old-old age (above 80 years). After ten sessions of practice on working memory tasks, the training group improved in four of the five trained tasks, emphasizing the potential for plasticity even in old-old age. The gains in the training group were largely driven by individuals who started out with a low capacity in the training tasks. Thus, findings suggest that working memory can be improved with a short executive control training even in old-old age, particularly for low-capacity individuals. The absence of transfer effects in this study may point to the limits of plasticity in this age group.
The third study aimed at further elucidating the mixed findings regarding the amounts of training and transfer effects induced by executive control training in older adults. For that purpose, a sample of older adults covering a wide range from young-old to old-old age (65 to 95 years) was either trained for nine sessions on a visuospatial and a verbal working memory as well as an executive control task; or served as controls. Analyses revealed significant training effects in all three trained tasks, as well as near transfer to verbal working memory and far transfer to a nonverbal reasoning task. Remarkably, all training effects and the transfer effect to verbal working memory were even stable at a nine-month follow-up. These findings suggest that cognitive plasticity is preserved over a large range of old age and that even a rather short training regimen can lead to (partly specific) training and transfer effects. However, analyses also revealed that there are a range of factors that may moderate the amount of plasticity, e.g., age and baseline performance in the training domain.
To summarize, the current thesis explored effects of short executive control trainings on cognitive functions in adolescents and older adults. The findings suggest a high potential for intraindividual variability across the whole life-span. Plasticity was shown on the level of training and transfer tasks, as well as on the level of stability of effects. Furthermore, results support the notion that process-based training improves executive control processes that in turn lead to improvements in tasks that rely on these processes. The current thesis makes important contributions to the conceptual debate about the potentials and limits of training-induced plasticity across the life-span. It benefits the debate in that it specifically delineates factors that moderate the obtained effects.:Abstract ..............................................................................................1
1 General Introduction .....................................................................3
1.1 Plasticity of cognitive functions ...................................................5
1.2 Executive control functions .........................................................6
1.3 Cognitive training of executive control functions .......................9
2 Outline and Central Questions ......................................................19
2.1 What amount of plasticity does executive control training induce in different age groups? .........................................................................19
2.2 Do training and transfer effects of executive control training remain stable over time? ....................................................................20
2.3 Do training design, age, and baseline performance moderate the amount of plasticity? ...........................................................................20
2.4 Are changes in trained tasks specifically related to changes in transfer tasks? .................................................................................21
3 Study 1 - Effects of a Task Switching Training in Adolescents .......22
3.1 Introduction ..............................................................................22
3.2 Methods ....................................................................................27
3.3 Results ......................................................................................33
3.4 Discussion .................................................................................43
4 Study 2 - Effects of a Working Memory Training in Old-Old adults .48
4.1 Introduction ...............................................................................48
4.2 Methods .....................................................................................51
4.3 Results .......................................................................................54
4.4 Discussion ..................................................................................59
5 Study 3 - Factors Moderating Effects of Working Memory Training in Older Adults .......................................................................63
5.1 Introduction ................................................................................63
5.2 Methods ......................................................................................67
5.3 Results .........................................................................................71
5.4 Discussion ...................................................................................78
6 General Discussion .........................................................................83
6.1 Summary of empirical findings .....................................................83
6.2 Integration of the main empirical findings ...................................85
6.3 Conclusion and Outlook ...............................................................95
6.4 Summary ......................................................................................98
References ..........................................................................................99
Appendix ............................................................................................112
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:26126 |
| Date | 20 July 2012 |
| Creators | Zinke, Katharina |
| Contributors | Kliegel, Matthias, Strobel, Alexander, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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