Erikson's stages of psychosocial development, as articulated in the second half of the 20th century by Erik Erikson in collaboration with Joan Erikson, is a comprehensive psychoanalytic theory that identifies a series of eight stages that a healthy developing individual should pass through from infancy to late adulthood. According to Erikson's theory the results from each stage, whether positive or negative, influences the results of succeeding stages. Erikson published a book called Childhood and Society around the 1950s that made his research well known on the eight stages of psychosocial development. Erikson was originally influenced by Sigmund Freud's psychosexual stages of development. He began by working with Freud's theories specifically, but as he began to dive deeper into biopsychosocial development and how other environmental factors affect human development, he soon progressed past Freud's theories and developed his own ideas. Erikson's stage theory characterizes an individual advancing through the eight life stages as a function of negotiating their biological and sociocultural forces. The two conflicting forces each have a psychosocial crisis which characterizes the eight stages. If an individual does indeed successfully reconcile these forces (favoring the first mentioned attribute in the crisis), they emerge from the stage with the corresponding virtue. For example, if an infant enters into the toddler stage (autonomy vs. shame and doubt) with more trust than mistrust, they carry the virtue of hope into the remaining life stages. The stage challenges that are not successfully overcome may be expected to return as problems in the future. However, mastery of a stage is not required to advance to the next stage. In one study, subjects showed significant development as a result of organized activities. Stages Hope: trust vs. mistrust (oral-sensory, infancy, under 1 year) Existential Question: Can I Trust the World? The first stage of Erik Erikson's theory centers around the infant's basic needs being met by the parents or caregiver and how this interaction leads to trust or mistrust. Trust as defined by Erikson is "an essential trustfulness of others as well as a fundamental sense of one's own trustworthiness." The infant depends on the parents, especially the mother, for sustenance and comfort. Infants will often use methods such as pointing to indicate their interests or desires to their parents or caregivers. The child's relative understanding of the world and society comes from the parents and their interaction with the child. Children first learn to trust