Studies that try to train specific cognitive abilities often only show task-specific improvements, and participants are unable to generalize their strategies to new tasks or problems. In 2016, there was some evidence that some of these programs improved performance on tasks in which users were trained, less evidence that improvements in performance generalize to related tasks, and almost no evidence that "brain training" generalizes to everyday cognitive performance. In addition, most clinical studies were flawed. But in 2017, the National Academies of Sciences, Engineering, and Medicine found moderate strength evidence for cognitive training as an intervention to prevent cognitive decline and dementia, and in 2018, the American Academy of Neurology guidelines for treatment of mild cognitive impairment included cognitive training.To address growing public concerns with regard to aggressive online marketing of brain games to older population, a group of scientists published a letter in 2008 warning the general public that there is a lack of research showing effectiveness of brain games in older adults.In 2010, the Agency for Healthcare Research and Quality found that there was insufficient evidence to recommend any method of preventing age-related memory deficits or Alzheimer's.In 2014 another group of scientists published a similar warning. Later that year, another group of scientists made a counter statement, organized and maintained by the Chief Scientific Officer of Posit. They compiled a list of published studies on efficacy of cognitive training across populations and disciplines.In 2014, one group of over 70 scientists stated that brain games cannot be scientifically proven as being cognitively advantageous, whether that be in preventing cognitive decline or improving cognitive functioning. Another group argued the opposite, with over 130 scientists saying that there is valid evidence in the benefits of brain training. The question is how these two groups reached different conclusions in reading the same literature. Different standards on both sides can answer that question. In a more specific manner, there is indeed a great deal of evidence that brain training does indeed improve performance on trained tasks, but less evidence in closely related tasks. There is even less evidence on distantly related tasks.In 2017, a committee of the National Academies of Sciences, Engineering, and Medicine released a report about the evidence on interventions for preventing cognitive decline and dementia.In 2017, a group of Australian scientists undertook a systematic review of what studies have been published of commercially available brain training programs in an attempt to give consumers and doctors credible information on which brain training programs are actually scientifically proved to work. After reviewing close to 8,000 studies about brain training programs marketed to healthy older adults, most programs had no peer reviewed published evidence of their efficacy. Of the seven brain training programs that did, only two of those had multiple studies, including at least one study of high quality: BrainHQ and CogniFit.In 2019, a group of researchers showed that claims of enhancement following brain training and other training programs have been exaggerated, based on a number of meta-analyses. Other factors, e.g., genetics, seem to play a bigger role.