The influence of training task stimuli on transfer effects of working memory training in aging

Introduction: Working memory (WM) training is known to produce benefits in older adults’ WM. Transfer effects to untrained abilities, however, remain controversial and several aspects are thought to influence the generalization of benefits, including the kind of stimuli used in the training tasks, an aspect rarely addressed in older adults. Objective: The present study had two aims: (1) to test the efficacy of a visuospatial WM training procedure in older adults, in terms of specific and transfer effects; (2) to examine in two experiments whether the type of stimuli used in the training task influences the training's effectiveness. Experiment 1 adopted images with a neutral valence while experiment 2 used emotionally positive images based on evidence that older adults tend to remember positive stimuli better. In both experiments, specific training-related gains in a visuospatial WM task (the criterion task) and transfer effects on measures of verbal WM, visuospatial short-term memory, processing speed and reasoning were examined. Maintenance of training benefits was also assessed at an 8-month follow-up. Method: Seventy older adult (63–75 years old) volunteers (35 for experiment 1, and 35 for experiment 2) were randomly assigned to a training or active control group. The same visuospatial WM training procedure was used in both experiments, manipulating only the type of stimuli used (neutral in experiment 1 and emotionally positive in experiment 2). Results: In both experiments, only trained participants showed specific benefits in the WM criterion task. These gains were also maintained at the follow-up, but no transfer effects were identified. Conclusion: Overall, our findings using the present visuospatial WM training paradigm suggest that it is less effective, in terms of transfer effects, than the same paradigm administered verbally in a previous study, regardless of the type of stimuli used in WM training tasks (neutral or emotionally positive stimuli).