Title: Cognitive training effects across the adult lifespan: A diffusion modelling approach
Funder: Economic and Social Research Council

Abstract: Fluid cognitive abilities such as processing speed, attentional control, and reasoning increase into adulthood and, shortly after peaking in the early 20s, begin to decline with progressing age (Craik & Bialystok 2006). In later adulthood, these profound age-related cognitive declines affect everyday life functioning and life satisfaction (Diehl 1998), which is particularly alarming given that the world's population of people over the age of 60 is continuously increasing (WHO 2017). Thus, it is critical to identify evidence-based and accessible interventions that can counteract these declines during adulthood and support maintaining cognitive health into later life. In recent years, cognitive training interventions have gained popularity as a cost-effective and easy-to-administer option for all ages. Overall, however, the cumulative empirical evidence regarding the effectiveness of cognitive training is weak. A notable successful exception appears to be training interventions targeting processing speed and attentional control, which have been shown to transfer to older adults' everyday functioning and may even delay the onset of dementia (for a review, see Edwards et al. 2018). These successful training interventions typically require participants to react as quickly and as accurately as possible to a stimulus, often in combination with attentional control demands such as the inclusion of a secondary task. However, the cognitive mechanisms underlying these training and transfer effects are yet unclear (Strobach & Karbach 2016). We propose that the key mechanism affected by processing speed training is the rate with which people extract information from the environment, and that improvements in this mechanism benefit performance more broadly in tasks assessing executive functions and intelligence. We further assume that these improvements are stronger with increasing attentional control demands of the training tasks, but these additive benefits of attentional control task components may vary with trainees' age. In the proposed project, we aim to systematically test these hypotheses. Moving beyond the limitations of traditional approaches, we will apply diffusion modelling, a computational approach that allows for distinguishing the rate of extracting information from the environment from other cognitive processes involved in performing these tasks. A better understanding of how processing speed training affects these cognitive mechanisms across the adult lifespan will enable researchers to maximise the effectiveness of cognitive training during adulthood in producing broad transfer to psychologically meaningful everyday life outcomes. The overarching goal of the proposed project is to identify the cognitive processes improved by training speed tasks with varying attentional control demands across the adult lifespan. This project goes substantially beyond previous research by using diffusion modelling to estimate theoretically and psychologically meaningful information processing components involved in performing the training tasks. In short, we pursue the following aims: 1. To examine how extensive speed training affects the involved cognitive processes reflected by changes in diffusion model parameters, and whether changes in cognitive processes vary across the adult lifespan. 2. To investigate how changes observed in these cognitive processes are related to transfer effects to working memory, reasoning, and everyday cognitive functioning, and whether these changes are maintained after the end of the training intervention. 3. To determine how attentional control demands of the training intervention modulate these effects.

Lay abstract: We all experience losses in memory and attention after our mental performance peaked around our 20s. Although this development is quite universal and difficult to reverse, there are ways to slow down losses in mental performance or at least to compensate for these losses. While pharmaceutical products counteracting this development are costly and can be associated with severe side effects, cognitive training is an affordable and easy-to-administer alternative to stay mentally fit. Cognitive training is a program of regular mental activities purported to maintain or improve one's mental abilities. In particular, the introduction of computerised cognitive training has broadened the possibilities, the diversity, and the availability of such training programs to the general audience. The general motivation behind cognitive training is the assumption that human cognitive functioning and the brain are plastic. However, critics asserted that scientific support for training-related plasticity is limited to the practiced tasks while there is no or only minimal benefit for tasks beyond the training context and in everyday life. One exception appears to be training programs that focus on improving processing speed. They usually include tasks in which trainees quickly decide between different choices. The present initiative uses a novel study design combined with an innovative computational approach to systematically investigate the benefits of processing speed training across adulthood. Besides providing robust tests of the promising effects of this type of training on cognitive functioning, this research will tackle an important yet so far unanswered question: How does processing speed training produce benefits? This research will yield important insights into how to maximise the benefits of cognitive training. First, a detailed analysis of performance in the trained tasks will reveal which changes in components of cognitive processing are essential to produce benefits in other contexts. With this knowledge, future training programs can be tailored to boost the relevant components more directly and effectively. Second, our research will determine the optimal level of training task complexity. For instance, processing speed tasks can require only little attention when they are performed in isolation, or they can demand our full attention in multitasking situations. As this may vary with people's age, we will examine the effects in adults ranging from young to old adulthood. The insights from this multi-site initiative with researchers from the UK, Germany, and Canada will allow for developing maximally effective training programs for improving attention, reasoning, and everyday cognitive functioning. With this initiative, we hope to improve our understanding of the human cognitive system, its plasticity, and ways to use this plasticity to compensate for age-related mental losses and enable people to live independently and cognitively healthy for longer.

Research activity codes: 1.2 PSYCHOLOGICAL AND SOCIOECONOMIC PROCESSES
Health categories: MENTAL HEALTH