Each stage is characterized by how the desire for pleasure in these erogenous zones and the demands of reality are resolved. An optimal amount of gratification in each stage resulted in a successful passing into the next stage and fixation, which is the over-investment of energy into a developmental stage's erogenous zone, would not occur which could lead to later maladaptive behavior.
According to Freud, a child in middle childhood would be in the latency stage where the child focuses on same sex friendships, internalizes sex specific behaviors, attitudes, and morality, and develops social and intellectual skills. An adolescent would be in the last stage of development, the genital stage where the focus is on heterosexual relationships with non-family members. At either of these stages, maladaptive behaviors can crop up if the child did not pass through previous stages with the optimum gratification.
Erik Erikson (1902-1994) forwarded and reinterpreted the concept of developmental stages. Erikson proposed that rather than psychosexual stages, humans develop in psychosocial stages and that these stages do not end at adolescence, but continue throughout life. According to Erikson, the stages are characterized by a unique crisis and only through the resolution of the crisis in each stage, could a well adapted person develop. Erikson's eight life-span stages are trust versus mistrust, autonomy versus shame and doubt, initiative versus guilt, industry versus inferiority, identity versus identity confusion, intimacy versus isolation, generativity versus stagnation, and integrity versus despair. Throughout all these stages, there is an emphasis on identity or in other words, the understanding of both the self and the society one lives in. One's identity is transformed from one stage to the next and is influenced by earlier stages.
According to Erikson, a child in middle childhood would most likely be in the industry versus inferiority stage.