Before we begin to discuss the specific developmental changes that occur during adolescence, it might be useful to provide a more general overview of the enormous magnitude and complexity of adolescent development since it encompasses so many different, yet inter-related, areas of maturity. Furthermore, since several renowned developmental theorists have influenced and informed our current understanding of adolescent development, we will briefly re-introduce these theorists to provide a context for our subsequent discussion of adolescent development. However, a more complete and detailed discussion about these pioneers of developmental theory these can be found in the General Child Developmental Article. The seminal works of these early theorists continue to spark scientific research, and this research further refines our understanding of human development.
Perhaps one of the most well-known developmental theorists is Jean Piaget. He developed his theory of children's cognitive development , and a related theory of children's moral development during the 1920's. However, Piaget's theories didn't gain popularity until the middle of the twentieth century. According to Piaget, children's cognitive abilities developed in a sequential, step-wise fashion and their cognitive development subsequently influenced their social awareness and moral maturity. Piaget believed cognitive development, much like physical development, followed a natural order of progression for our species, and its trajectory was not affected by external forces. However, Piaget conceded that in the later stages of development children's social environment could influence the developmental process.
Lawrence Kohlberg came on the scene in the late 1950's when he first published his theory of moral development. Unlike Piaget who assigned only a minor role to the social environment, Kohlberg believed that social relationships and culture were central to understanding children's cognitive and moral development. However, like Piaget, Kohlberg believed moral development proceeded in sequential stages.
Another influential, developmental theorist of this era was Erik Erikson who proposed his psychosocial theory human development. Unlike Piaget and Kohlberg, Erikson's theory spans the entire lifecycle and therefore considers the developmental process to be an ongoing, life-long process. According to Erikson's theory, people must pass through sequential developmental stages, or "crises", during which they either develop the necessary skills to become successful, happy members of society; or, they fail to successfully navigate the crisis and remain "stuck" at that developmental stage.
Later, in the mid-60s James Marcia chimed in with his identity status theory. Marcia was particularly interested in the way adolescents develop their own individual identity within the framework of their families and larger culture. Unlike the theorists before him, Marcia did not rely upon a linear, sequential model of development.
While each of these theorists focused on specific aspects of human development (e.g., cognitive development, moral development, and identity development) collectively, their theories provide insight into the enormous complexity of human development. Perhaps more importantly, these theories enable us to recognize the inter-related aspects of development while providing a platform from which to measure and investigate the various dimensions of adolescent development. These dimensions include: physical, cognitive, emotional, social, moral, and sexual development.
Physically, adolescents' grow to reach their adult height and their bodies change in shape and composition due to the hormonal changes of puberty. Youth continue to become physically stronger, and to improve both gross and fine motor skills. Puberty triggered other physical changes such as the development of primary sex characteristics (characteristics directly related to reproductive functioning) and secondary sex characteristics (such as changes in body hair, voice, and sweat glands) and this maturation process continues during adolescence.