Positive psychology is a branch of psychology that studies the conditions that contribute to the optimal functioning of people, groups, and institutions. It studies "positive subjective experience, positive individual traits, and positive institutions... it aims to improve quality of life." It is a field of study that has grown as individuals and researchers look for common ground on better well-being. Positive psychology began as a new domain of psychology in 1998 when Martin Seligman chose it as the theme for his term as president of the American Psychological Association. It is a reaction against past practices, which tended to focus on mental illness and emphasized maladaptive behavior and negative thinking. It builds on the humanistic movement by Abraham Maslow, Rollo May, James Martin, and Carl Rogers, which encourages an emphasis on happiness, well-being, and positivity. Positive psychology largely relies on concepts from the Western philosophical tradition, such as the Aristotelian concept of eudaimonia, which is typically rendered in English with the terms "flourishing", "the good life" or even "happiness". Positive psychologists study empirically the conditions and processes that contribute to flourishing, subjective well-being and happiness - often using these terms interchangeably. Positive psychologists suggested a number of factors may contribute to happiness and subjective well-being, for example: social ties with a spouse, family, friends, colleagues, and wider networks; membership in clubs or social organizations; physical exercise; and the practice of meditation. Spirituality can also lead to increased individual happiness and well-being. Spiritual practice and religious commitment is a possible source for increased well-being studied within positive psychology. Happiness may rise with increasing income, though it may plateau or even fall when no further gains are made or after a certain cut-off amount.