The three target articles provide examples of intervention studies that are excellent models for the field. They rely on rigorous and elegant designs, the interventions are motivated by attention to underlying theoretical mechanisms, and longitudinal designs are used to examine the duration of effects of interventions that occur. When studies are carefully designed, effect sizes tend to be modest. We argue that the meaningfulness of effect sizes should not necessarily be determined with reference to Cohen's rule of thumb, and that modest effect sizes can result in major change in performance if they cumulate.