Criminal Justice Essay Paper on Lifespan Development and Personality in Adults Aged 18 to 40

Lifespan Development and Personality in Adults Aged 18 to 40


Growth and development is an essential aspect of living things because it is an indication that they are responding to physical change. In a normal situation, development is most noticeable in children because they are undergoing rapid physical and mental change. However, growth and development takes place even in adults and are affected by a number of factors. This paper explores factors that affect the development in adults between 18 and 40 years.

Factors That Affect Physical Development in Adult

At 18 year old, one is almost fully developed in size. At this time, one is considered as a young adult and thus the society sees him or her as a mature person. However, there is still a considerable physical growth at this stage, and this process continues at during early adulthood. Physical development is affected by both genetic and environmental factors.

Environmental Factors

There is no much noticeable physical development between the age of 18 and 40. The main physical development caused by the environment is an increase or decrease in height. Change in skin tone, muscle development, and personal grooming, such as the size of nails and hairs are also noticeable. Among the environmental factors that affect physical development at this stage is eating behaviors. Different environmental upbringing influences one’s eating behaviors. One may be exposed to junk foods from fast food cafes, whereas others may be exposed to a balanced diet. Those exposed to junk foods eventually grows fat, whereby they increase in size and weight. At the same time, those exposed to poor diet, such as poor feeding may reduce in size and weight during this stage.

Physical exercises also affect physical development at this stage. People who are exposed to an environment where they exercise a lot tone their muscles and enhance their physical appearance. In this case, noticeable change may be witnessed in the form of developed muscles and athletic bodies. Personal grooming may also lead to physical development. According to Santrock (2010), behavioral factors, such as personal grooming may lead to change in physical appearances during this stage. One may grow hair, nails of desired length, and color them as it befits his or her environmental status. Some may also tone their skin color depending on the environmental. 

Hereditary Factors

Genetics also plays a part in physical development. However, such changes are not much and are sometimes accompanied by environmental factors. For instance, obesity, which is a noticeable physical development, is caused by both environmental and genetic factors. At the same time, balding, which is also a noticeable physical development during this stage, is caused by genetic factors, whereby it can be inherited from one person to another (Santrock, 2010).

Cognitive Development

From 18 years old, one begins to develop realistic thinking habits, whereby there is a simplistic perception of the right from the wrong. They develop the view that there is more than one answer to a given situation, and this gives them a sense of maturity in their cognitive development. As they approach late 20s, they begin to specialize in their careers because of creativity.  As they attain 35 years, the cognitive development reaches its peak. As they reach 40, they become more focused in their goals with a slight failure in memory (Caspi & Roberts, 2001). Both hereditary and environmental factors play a role.

Environmental Factors

A number of environmental factors affect the cognitive development of adults, and the first one is education. Poorly educated young adults have a narrow view of thinking. Although most of them are supposed to have finished school, learning is a lifetime venture, and thus those with low education have poorly developed mental capacities. Economic activities may translate to good or poor cognitive development. Those with low economic status have little access to empowerment activities and thus have a poorly developed cognitive ability. However, poor economic development can motivate one into positive thinking to embitter the situation.

Hereditary Factors

Some factors inherited from parents can be responsible for cognitive development. According to Czerwinski, S. et al. (2007), a mentally retarded person can pass his or her genes to the offspring and such mental conditions affects the offspring even during the adulthood. At the same time, some diseases that affect the mind, such as schizophrenia are hereditary, and thus their effects can manifest in adulthood.

Factors That Affect Social, Moral, and Personality Development in Adult

Erickson’s Theory of Stages of Development

A number of factors that are mainly caused by the environment affect social, moral, and personality development in adult. According to Erickson’s theory of stages of development, young adults between 18 and 35 undergo social and psychological development at a high rate. They focus on love and companionship and start settling down in marriage. Most young people between these stages seek for intimacy, but if it fails, they isolate themselves. This means marital partners and friends are the most important factors that affect their development (Caspi & Roberts, 2001). 

At the age of 35 to 40, people tend to focus on family and career as ascertain by Erickson’s theory. The individual at this stage is fully mature and thus takes up greater roles and responsibilities. Erickson states that people at this stage attempts to bring something back to the society, and this may be their main concern. They fear being termed as meaningless or inactive and thus focus on doing something to the society, as well as the family (Santrock, 2010). The main factors that affect their development during this stage are thus opportunities and the sociopolitical environment surrounding them.

Daniel Levinson’s theory of adult development

Levinson, a Yale graduate psychologist, described the social, personality, and moral development of an adult through this theory. His theory has two concepts, and the first one is the stable period, which is the time one makes crucial decisions. The second concept is the transition period, which is the period between the end and the beginning of a new chapter in life. This means the moral, social, and personal aspect of an individual are affected by these two concepts in this theory (Santrock, 2010).

Daniel Levinson’s theory has several stages of development, and the first one is early adult transition, which occurs between 17 and 22 years. During this stage, the young adults make some preliminary choices towards adult life, and this is determined by various factors, such as peer pressure, parental guidance, and level of education. The second stage is the time for entering the adult world and occurs between the age of 22 and 28. During this stage, adults make a decision on occupation, values, friendships, lifestyle, and love. The third stage is age 30 transition, which takes place between the age of 28 and 33. The fourth stage is the stage of settling down, which takes place between the age of 33 and 40. At this stage, the adults have settled down and thus they are expected to make mature decisions. During this stage, their moral and social, as well as personality traits have matured, and thus they are not swayed by the prevailing situation (Caspi & Roberts, 2001). The decisions they make are calculated and sound.


Caspi, A., & Roberts, W. (2001). Personality development across the life course: The argument for change and continuity. Psychological Inquiry, 12 (2), 49-66.

Czerwinski, S. et al. (2007). Genetic factors in physical growth and development and their relationship to subsequent health outcomes. Am J Hum Biol , 19 (5), 684-691.

Santrock, J. (2010). Life-Span Development . New York: McGraw-Hill.