Sensorimotor stage: The first stage in Piaget's theory of cognitive development, where infants learn through their senses and motor actions.
Trust vs. mistrust: According to Erikson's psychosocial theory, this is the first stage in which an infant develops a sense of trust or mistrust based on how well their needs are met by their caregivers.
Object permanence: The understanding that objects continue to exist even when they cannot be seen or heard.