The ACTIVE study evaluated the effectiveness of three cognitive training interventions—memory, reasoning, and speed of processing—in improving cognitive abilities and daily functioning in older adults. A total of 2832 participants aged 65–94 years were randomly assigned to four groups: three intervention groups (memory, reasoning, speed of processing) and a control group. Each intervention group received 10 sessions of training, with a booster session offered to 60% of participants 11 months later. The study followed participants for two years, assessing cognitive function and daily functioning. Results showed that all three interventions improved the targeted cognitive abilities compared to baseline, with effects lasting up to two years. Booster training enhanced these gains, particularly in speed and reasoning, which were maintained at the two-year follow-up. However, no significant training effects were found on everyday functioning. The cognitive improvements were comparable to the expected decline in cognitive abilities in older adults without dementia over 7–14 years. The study highlights the durability of cognitive training effects, with improvements in cognitive abilities lasting up to two years. Training effects were equivalent to the expected decline in cognitive function for older adults without dementia. However, no significant differences in everyday functioning were observed, suggesting that longer follow-up may be needed to assess training effects on daily function. The study used a randomized, controlled, single-blind design with multiple outcome measures, including cognitive abilities and daily functioning. The results support the effectiveness of cognitive training in improving specific cognitive abilities, with effects comparable to the natural decline in cognitive function in older adults. The study also emphasizes the importance of using appropriate control groups and considering the generalizability of training findings. Overall, the ACTIVE study provides strong evidence for the effectiveness of cognitive training in improving cognitive abilities in older adults.The ACTIVE study evaluated the effectiveness of three cognitive training interventions—memory, reasoning, and speed of processing—in improving cognitive abilities and daily functioning in older adults. A total of 2832 participants aged 65–94 years were randomly assigned to four groups: three intervention groups (memory, reasoning, speed of processing) and a control group. Each intervention group received 10 sessions of training, with a booster session offered to 60% of participants 11 months later. The study followed participants for two years, assessing cognitive function and daily functioning. Results showed that all three interventions improved the targeted cognitive abilities compared to baseline, with effects lasting up to two years. Booster training enhanced these gains, particularly in speed and reasoning, which were maintained at the two-year follow-up. However, no significant training effects were found on everyday functioning. The cognitive improvements were comparable to the expected decline in cognitive abilities in older adults without dementia over 7–14 years. The study highlights the durability of cognitive training effects, with improvements in cognitive abilities lasting up to two years. Training effects were equivalent to the expected decline in cognitive function for older adults without dementia. However, no significant differences in everyday functioning were observed, suggesting that longer follow-up may be needed to assess training effects on daily function. The study used a randomized, controlled, single-blind design with multiple outcome measures, including cognitive abilities and daily functioning. The results support the effectiveness of cognitive training in improving specific cognitive abilities, with effects comparable to the natural decline in cognitive function in older adults. The study also emphasizes the importance of using appropriate control groups and considering the generalizability of training findings. Overall, the ACTIVE study provides strong evidence for the effectiveness of cognitive training in improving cognitive abilities in older adults.