Brain training (also called cognitive training) is a program of regular activities purported to maintain or improve one's cognitive abilities. The phrase “cognitive ability” usually refers to components of fluid intelligence such as executive function and working memory. Cognitive training reflects a hypothesis that cognitive abilities can be maintained or improved by exercising the brain, analogous to the way physical fitness is improved by exercising the body. Cognitive training activities can take place in numerous modalities such as cardiovascular fitness training, playing online games or completing cognitive tasks in alignment with a training regimen, playing video games that require visuospatial reasoning, and engaging in novel activities such as dance, art, and music.Numerous studies have indicated that aspects of brain structure remain "plastic" throughout life. Brain plasticity reflects the ability for the brain to change and grow in response to the environment. There is ample debate within the scientific community on the efficacy of brain training programs and controversy on the ethics of promoting brain training software to potentially vulnerable subjects.