A tale of two ages: fluid reasoning as a predictor of working memory training efficacy in middle-aged and older adults

Research on working memory (WM) training reveals significant variability in training effects, indicating that pretraining cognitive abilities might account for these differences. However, consensus on whether higher (magnification account) or lower (compensation account) pretraining abilities predict greater training effects remains elusive. Our study aimed to clarify the role of fluid reasoning in predicting training performance (i.e. training scores at each session) and gains on near transfer WM tasks. We conducted two studies: Study 1 focused on middle-aged adults (47-65 years) and Study 2 on older adults (65-83 years). Participants in both studies were randomly assigned to either adaptive n-back training or an active control group and have all completed three WM tasks before and after 20 training sessions - the trained n-back task and two structurally different untrained tasks. Generally, greater average training scores were found in individuals with higher fluid reasoning for both age groups, although this trend did not reach statistical significance in older adults. Similarly, higher fluid reasoning predicted greater training gains only in the sample of middle-aged adults. Further analysis showed that both, middle-aged and older participants in the training groups exhibited higher gains on the trained n-back task but not on two other WM tasks. Additionally, fluid reasoning predicted n-back gains in both the training and control group. Consistent with a growing body of research, our results show limited generalization of training effects across untrained tasks. It seems that factors beyond pretraining ability should be considered when explaining between-participant differences in training performance.