The word adultism was used by Patterson Du Bois in 1903, and appears in French psychology literature in 1929, describing the influence of adults over children. It was seen as a condition wherein a child possessed adult-like "physique and spirit", and was exemplified by,
- A boy of 12 and a girl of 13 who had the spirit and personality of adults.... They were placed in institutions because of stealing and prostitution. These forms of precocity lead the individual into difficulties and should be recognized early in the development of the individual.
This definition was superseded by a late 1970s journal article proposing that adultism is the abuse of the power that adults have over children. The author identified examples of adultism not only in parents but in teachers, psychotherapists, the clergy, police, judges, and juries.
Adultism is defined as the "behaviors and attitudes based on the assumptions that adults are better than young people, and entitled to act upon young people without agreement". It is also seen as, "an addiction to the attitudes, ideas, beliefs, and actions of adults." Adultism is popularly used to describe any discrimination against young people and is distinguished from ageism, which is simply prejudice on the grounds of age; not specifically against youth. Adultism is ostensibly caused by fear of children and youth. It has been suggested that 'adultism, which is associated with a view of the self that trades on rejecting and excluding child-subjectivity, has always been present in Western culture'.
Fletcher suggests that adultism has three main expressions throughout society:
- Attitudinal Adultism: Personal feelings, assumptions, and beliefs that form a person's attitudes about young people. This is also called internalized adultism.
- Cultural Adultism: The shared attitudes, including beliefs and customs, promoting the assumption that adults are superior to anyone who is not identified as an adult, simply because of their age. This is also called social adultism.
- Structural Adultism: The normalization and legitimization of historical, cultural, institutional and interpersonal dynamics that routinely advantage adults while producing cumulative and chronic adverse outcomes for young people. This is also referred to as institutional adultism.
A study by the Crisis Prevention Institute of the prevalence of adultism found an increasing number of local youth-serving organizations addressing the issue. For instance, a local program in Oakland, California, describes the impact of adultism, which "hinders the development of youth, in particular, their self-esteem and self-worth, ability to form positive relationships with caring adults, or even see adults as allies", on their website.
Adultism is used to describe the oppression of children and young people by adults, which is seen as having the same power dimension in the lives of young people as racism and sexism. It is treated as a generalization of paternalism, allowing for the broad force of adulthood beyond males, and may be witnessed in the infantalization of children and youth. Pedophobia (the fear of children) and ephebiphobia (the fear of youth) have been proposed as the antecedents to adultism. Gerontophobia, or its antonym, gerontocracy, may be extensions of adultism.
Similar terms such as adult privilege, adultarchy, and adultcentrism have been proposed as alternatives which are more morphologically parallel. Some activists alternatively call adultism "youthism," or "childism" equating it to sexism and heterosexism. The opposite of adultism is jeunism, which is defined as the preference of young people and adolescents over adults.
At least one prominent organization describes discrimination against youth as ageism, which is any form of discrimination against anyone due to their age. The National Youth Rights Association argues that ageism is a more natural and understandable term than adultism and thus is more commonly used among the young people affected by this discrimination. Advocates of using 'ageism' also believe it makes common cause with older people fighting against their own form of age discrimination. However, a national organization called Youth On Board counters this, arguing that "addressing adultist behavior by calling it ageism is discrimination against youth in itself."