Different control activities are used in different trials. We use control activities that ensure that the improvements that we see in individuals using our training program are specifically due to the unique science of our training programs, and not, for example, due to a “placebo effect” (meaning that participants show improvements just because they believe the training program might be helpful), or due to general cognitive stimulation (which any activity might provide). Our control activities are designed to be plausibly helpful to people (so that they engage the placebo effect), and to provide cognitive stimulation through learning (so that they provide a meaningful comparison to our training program). In addition, our control activities are time-matched, computer-matched, and social-contact matched to our training programs, ensuring that these factors are not by themselves responsible for the gains we see with our training programs. For example, we have used educational DVDs with daily quizzes to test learning as a control activity, because they provide plausible benefit to participants through learning of facts, they match current doctors’ recommendations for staying cognitively active (i.e., people are often advised to “stay cognitively active” for brain fitness), participants have high engagement with this activity (resulting in a low dropout rate from the study), and they can be matched for time on a computer. Other control or comparison activities have also been used in the studies, including computer games, audio books, internet surfing, reasoning classes, and memory classes. Some studies also have been run with “no contact” controls, which are control groups who engage in no special activity during the study period but are matched to the study group and tested before and after.