Cognitive training has been studied by scientists for the past 100 years.Cognitive training includes interventions targeted at improving cognitive abilities such as problem-solving, reasoning, attention, executive functions, and working memory. These kinds of abilities are targeted because they are correlated with individual differences such as academic achievement and life outcomes and it is thought that training general cognitive functions will lead to transfer of improvement across a variety of domains. Cognitive reserve is the capacity of a person to meet the various cognitive demands of life and is evident in an ability to assimilate information, comprehend relationships, and develop reasonable conclusions and plans. Cognitive training includes interventions targeted at improving cognitive abilities. One hypothesis to support cognitive training is that certain activities, done regularly, might help maintain or improve cognitive reserve.Cognitive training studies often target clinical groups such as people with neurodegenerative disorders such as Alzheimer's and children with ADHD that experience general cognitive deficits. More broadly, it is thought that cognitive training may especially benefit older adults as there is a general decline in fluid intelligence with age as there are decreases in speed of processing, working memory, longterm memory, and reasoning skills. Some researchers argue that the lower performance of older adults on cognitive tasks may not always reflect actual ability as older adults may show performance decrements due to strategy choice, such as avoiding using memory retrieval in memory tasks.