The developmental theories presented in this chapter focus on the psychosocial, cognitive, and moral growth (addition of new skills) and development (improvement of existing skills) of an individual throughout the life span. Psychosocial growth and development is explained using the works of Erikson. Cognitive development is explained using Piaget theory, and moral development is described using Kohlberg theory.

Erikson (1963) developed the psychosocial theory, which is defined as the intrapersonal and interpersonal responses of a person to external events (Schuster & Ashburn, 1992). Erikson concluded that societal, cultural, and historic factors as well as biophysical processes and cognitive function influence personality development (Erikson, 1968). He declared that the ego not only mediates between the id’s abrupt impulses and the superego’s moral demands but also can positively affect a person’s development as more skills and experience are gained. Erikson believed that personality development continues to evolve throughout the life span. He identified eight stages of the life span through which a person may sequentially develop (see Table 4-1). Each stage (or achievement level) proposed has a central developmental task called a crisis. Crises are dilemmas composed of opposing viewpoints (e.g., basic trust vs. basic mistrust). If a person resolves the challenge in favor of the more positive of the two viewpoints (e.g., emphasis on basic trust), then that person achieves resolution of the developmental task. The person must negotiate a healthy balance between the two concepts in order to move to the next stage and eventually become a well-adjusted adult in society. For example, a person needs some basic mistrust in some situations (e.g., stay a safe distance from blazing flames, cautiously approach an unfamiliar animal). Positive resolution for a crisis in one stage is necessary for positive resolution in the next stage. Erikson proposed that strengths emerge with the positive resolution of each crisis. If a task is only partially resolved, then a person experiences difficulty in subsequent developmental tasks. These issues must be remediated to realize one’s psychosocial potential. Erikson did not use chronologic boundaries but assigned developmental levels throughout the life span, which each person develops at their own rate based on potential and experiences (see Table 4-1).

Dr. Piaget (1970) explained the growth and development of intellectual structures. He focused on how a person learns and recognized that interrelationships of physical maturity, social interaction, environmental stimulation, and experiences were necessary for cognitive development. To explain his theory, he applied the concepts of schema (plural: schemata), assimilation, accommodation, and equilibration (equilibrium). A schema is a unit of thought that may consist of a thought, emotional memory, movement of a part of the body, or a sensory experience (such as making use of sight, hearing, taste, smell, or touch). Schemata can be categorized using either assimilation or accommodation. Assimilation is an adaptive process whereby a stimulus or information is incorporated into an already existing schema. Another way of saying this is the person changes reality into what they already know. For example, a toddler, who knows their pet cat to be a "Kitty," sees a dog for the first time and thinks the new animal is called "Kitty." Accommodation is the creation of a new schema or the modification of an old one to differentiate more accurately a stimulus or a behavior from an existing schema. One changes the self to fit reality. The same toddler may meet other cats and modify "Kitty" to "cat" and eventually, with experience and guidance, meet more dogs and create the idea of "dog." Equilibration is the balance between assimilation and accommodation. When disequilibrium occurs, it provides motivation for the individual to assimilate or accommodate further. A person who only assimilated stimuli would not be able to detect differences in things; a person who only accommodated stimuli would not be able to detect similarities. Piaget emphasized that schemata, assimilation, accommodation, and equilibration are all essential for cognitive growth and development. Piaget (1970) postulated that a person may progress through four major stages of intellectual development beginning at birth. Ages are not attached to these stages since each person progresses at their own rate. At each new stage, previous stages of thinking are incorporated and integrated. If a person attained formal operational thinking (see Table 4-2), they declare that qualitative changes in thinking cease and quantitative changes in the content and function of thinking may continue.

Lawrence Kohlberg, a psychologist, developed a theory of moral development. He proposed that morality is a dynamic process that extends over one’s lifetime, involving the affective and cognitive domains in determining what is "right" and "wrong." Dr. Kohlberg examined the reasoning a person uses to make a decision, as opposed to the action that results after that decision is made. Moral development is influenced by cognitive structures, but not in the same way as cognitive development. Kohlberg viewed justice (or fairness) as the goal of moral judgment.

Kohlberg (Colby et al., 1983) proposed three levels of moral development that encompass six stages (see Table 4-3). He believed that few people progress past the second level. Asserting that moral development extends beyond adolescence, he saw moral decisions and reasoning becoming increasingly differentiated, integrated, and universalized (i.e., independent of culture) at each successive stage. A person must enter their moral stage hierarchy in an ordered and irreversible sequence with no relationship to biologic age. He concluded that a person may never attain a higher stage of moral development and thus not ascend this proposed hierarchy of stages. He believed part of this was determined by how much a person is challenged with decisions of a higher order. Kohlberg did not theorize that infants and young toddlers were capable of moral reasoning. He viewed them as being naïve and egocentric.