Why is physical development important in early adulthood?

As we age, our bodies change in physical ways. One can expect a variety of changes to take place through the early- and middle-adult years. Each person experiences age-related changes based on many factors: biological factors such as molecular and cellular changes are called primary aging, while aging that occurs due to controllable factors, such as lack of physical exercise and poor diet, is called secondary aging.

As an individual progresses through adulthood, a variety of factors can affect the aging process. This includes primary factors like decline of cellular function and oxidative damage, and secondary factors like an unhealthy lifestyle.

By the time we reach early adulthood, our physical maturation is complete, although our height and weight may increase slightly. In early adulthood, our physical abilities are at their peak, including muscle strength, reaction time, sensory abilities, and cardiac functioning. Most professional athletes are at the top of their game during this stage, and many women have children in the early-adulthood years.

The aging process, although not overt, begins during early adulthood. Around the age of 30, many changes begin to occur in different parts of the body. For example, the lens of the eye starts to stiffen and thicken, resulting in changes in vision (usually affecting the ability to focus on close objects). Sensitivity to sound decreases; this happens twice as quickly for men as for women. Hair can start to thin and become gray around the age of 35, although this may happen earlier for some individuals and later for others. The skin becomes drier and wrinkles start to appear by the end of early adulthood. The immune system becomes less adept at fighting off illness, and reproductive capacity starts to decline.

During middle adulthood, the aging process becomes more apparent. Around the age of 60, the eyes lose their ability to adjust to objects at varying distances, known as presbyopia. Most people between the ages of 40 and 60 will need some form of corrective lenses for vision deficits. Middle-aged adults are also at higher risk than younger adults for certain eye problems, such as glaucoma. Hearing also further declines: 14 percent of middle-aged Americans have hearing problems. Skin continues to dry out and is prone to more wrinkling, particularly on the sensitive face area. Age spots and blood vessels become more apparent as the skin continues to dry and get thinner. The muscle-to-fat ratio for both men and women also changes throughout middle adulthood, with an accumulation of fat in the stomach area.

Women experience a gradual decline in fertility as they approach the onset of menopause—the end of the menstrual cycle—around 50 years old. This process involves hormonal changes and may last anywhere from six months to five years. Because of the shifting hormone levels, women going through menopause often experience a range of other symptoms, such as anxiety, poor memory, inability to concentrate, depressive mood, irritability, mood swings, and less interest in sexual activity. 

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Because we spend so many years in adulthood (more than any other stage), cognitive changes are numerous during this period. In fact, research suggests that adult cognitive development is a complex, ever-changing process that may be even more active than cognitive development in infancy and early childhood (Fischer, Yan, & Stewart, 2003).

Unlike our physical abilities, which peak in our mid-20s and then begin a slow decline, our cognitive abilities remain relatively steady throughout early and middle adulthood. Research has found that adults who engage in mentally and physically stimulating activities experience less cognitive decline in later adult years and have a reduced incidence of mild cognitive impairment and dementia (Hertzog, Kramer, Wilson, & Lindenberger, 2009; Larson et al., 2006; Podewils et al., 2005).

Beyond Piaget's Theory 

According to Jean Piaget's theory of cognitive development, the establishment of formal operational thinking occurs during early adolescence and continues through adulthood. Unlike earlier concrete thinking, this kind of thinking is characterized by the ability to think in abstract ways, engage in deductive reasoning, and create hypothetical ideas to explain various concepts. 

Since Piaget's theory, other developmental psychologists have suggested a fifth stage of cognitive development, known as postformal operational thinking (Basseches, 1984; Commons & Bresette, 2006; Sinnott, 1998). In postformal thinking, decisions are made based on situations and circumstances, and logic is integrated with emotion as adults develop principles that depend on contexts. This kind of thinking includes the ability to think in dialectics, and differentiates between the ways in which adults and adolescents are able to cognitively handle emotionally charged situations.

Early Adulthood

During early adulthood, cognition begins to stabilize, reaching a peak around the age of 35. Early adulthood is a time of relativistic thinking, in which young people begin to become aware of more than simplistic views of right vs. wrong. They begin to look at ideas and concepts from multiple angles and understand that a question can have more than one right (or wrong) answer. The need for specialization results in pragmatic thinking—using logic to solve real-world problems while accepting contradiction, imperfection, and other issues. Finally, young adults develop a sort of expertise in either education or career, which further enhances problem-solving skills and the capacity for creativity. 

Middle Adulthood

Two forms of intelligence—crystallized and fluid—are the main focus of middle adulthood. Our crystallized intelligence is dependent upon accumulated knowledge and experience—it is the information, skills, and strategies we have gathered throughout our lifetime. This kind of intelligence tends to hold steady as we age—in fact, it may even improve. For example, adults show relatively stable to increasing scores on intelligence tests until their mid-30s to mid-50s (Bayley & Oden, 1955). Fluid intelligence, on the other hand, is more dependent on basic information-processing skills and starts to decline even prior to middle adulthood. Cognitive processing speed slows down during this stage of life, as does the ability to solve problems and divide attention. However, practical problem-solving skills tend to increase. These skills are necessary to solve real-world problems and figure out how to best achieve a desired goal.

Cognitive ability changes over the course of a person's lifespan, but keeping the mind engaged and active is the best way to keep thinking sharp.

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There are many theories about the social and emotional aspects of aging. Some aspects of healthy aging include activities, social connectedness, and the role of a person’s culture. According to many theorists, including George Vaillant (2002), who studied and analyzed over 50 years of data, we need to have and continue to find meaning throughout our lives. 

For those in early and middle adulthood, meaning is often found through work (Sterns & Huyck, 2001) and family life (Markus, Ryff, Curan, & Palmersheim, 2004). These areas relate to the tasks that Erik Erikson referred to as generativity vs. stagnation and intimacy vs. isolation. 

Relationships in Adulthood

Positive relationships with significant others in our adult years have been found to contribute to a state of well-being (Ryff & Singer, 2009). Most adults in the United States identify themselves through their relationships with family—particularly with spouses, children, and parents (Markus et al., 2004). While raising children can be stressful, especially when they are young, research suggests that parents reap the rewards down the road, as adult children tend to have a positive effect on parental well-being (Umberson, Pudrovska, & Reczek, 2010). Having stable intimate relationships has also been found to contribute to well-being throughout adulthood (Vaillant, 2002).

A lack of positive and meaningful relationships during adulthood can result in what Erikson termed the crisis of intimacy vs. isolation in his theory of psychosocial development. In young adulthood (i.e., 20s and early 30s), people tend to be concerned with forming meaningful relationships; young and middle-aged adults are subject to loneliness if they are unable to form meaningful relationships with family, friends, or community. 

Social relationships are important to overall well-being in early and middle adulthood. (credit: Philippe Put)

Crises of Adulthood

Both early and middle adulthood come with particular challenges; these challenges are at times referred to as "quarter-life crises" and "mid-life crises," respectively. A quarter-life crisis typically occurs between the ages of 25 and 30. It often revolves around the challenges that arise from young adults newly living life on their own and feeling overwhelmed with new responsibilities; it can also happen after the birth of a child or if a person graduates from college and cannot find a job in their chosen field. In this stage of life, young people may worry about their future, wonder if they've made poor choices, or wonder what life might hold for them now. 

The main triggers for a mid-life crisis include problems with work, trouble in a marriage, children growing up and leaving the home, or the aging or death of a person's parents. This is likely to occur during Erikson's stage of generativity vs. stagnation, a time when people think about the contribution they are making to the world. Generativity involves finding one's life’s work and contributing to the development of others through activities such as volunteering, mentoring, and raising children; those who do not master this task may experience a feeling of stagnation.

Individuals having a mid-life crisis may experience some of the following:

• a search for an undefined dream or goal;
• a deep sense of regret for goals not accomplished;
• a fear of humiliation among more successful colleagues;
• a desire to achieve a feeling of youthfulness;
• a need to spend more time alone or with certain peers.

Some who experience a quarter- or mid-life crisis struggle with how to cope and may engage in harmful behaviors, such as abuse of alcohol or drugs or excessive spending of money. Others may experiment with different aspects of their personality, explore new hobbies, or otherwise seek out change in their lives.

Finding Meaning Through Work

Many adults find meaning in and define themselves by what they do—their careers. Earnings peak for many during adulthood, yet research has found that job satisfaction is more closely tied to work that involves contact with other people, is interesting, provides opportunities for advancement, and allows some independence (Mohr & Zoghi, 2006) than it is to salary (Iyengar, Wells, & Schwartz, 2006). 

Erikson's stage of generativity vs. stagnation revolves around a person's sense of their contribution to the world. Generativity is about making life productive and creative so that it matters to others, especially those in the next generation. According to Erikson, a person who is self-centered and unable or unwilling to help society move forward develops a feeling of stagnation—a dissatisfaction with the relative lack of productivity. The central tasks during middle adulthood can include expressing love through more than sexual contacts, maintaining healthy life patterns, helping growing and grown children to be responsible adults, relinquishing a central role in the lives of grown children, creating a comfortable home, being proud of one's accomplishments, taking care of aging parents, adjusting to the physical changes of middle age, and using leisure time creatively.

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Positive relationships with significant others in our adult years have been found to contribute to a state of well-being (Ryff & Singer, 2009). Most adults in the United States identify themselves through their relationships with family—particularly with spouses, children, and parents. An interpersonal relationship is a strong, deep, or close association or acquaintanceship between two or more people that may range from brief to enduring in duration. Like people, relationships change and grow; they may either improve or dissipate over time. The association between two people can be based on various factors—love, solidarity, business, or any other context that requires two (or more) people to interact.

Interpersonal relationships take many forms in many different cultures.

Interpersonal relationships are dynamic systems that change continuously during their existence. Like living organisms, relationships have a beginning, a lifespan, and an end. They tend to grow and improve gradually as people get to know each other and become closer emotionally, or they gradually deteriorate as people drift apart. 

Levinger's Model of Relationships

One of the most influential models of relationship development was proposed by psychologist George Levinger. This model was formulated to describe heterosexual, adult romantic relationships, but it has been applied to other kinds of interpersonal relationships since then. According to the model, the natural development of a relationship follows five stages:

1. Acquaintance and Acquaintanceship: Becoming acquainted depends on previous relationships, physical proximity, first impressions, and a variety of other factors. If two people begin to like each other, continued interactions may lead to the next stage, but acquaintance can continue indefinitely. Another example is association.
2. Buildup: During this stage, people begin to trust and care about each other. The need for intimacy, compatibility, and such filtering agents as common background and goals will influence whether or not interaction continues.
3. Continuation: This stage follows a mutual commitment to strong and close long-term friendships, romantic relationship, or even marriage. It is generally a long, relatively stable period. Nevertheless, continued growth and development will occur during this time. Mutual trust is important for sustaining the relationship.
4. Deterioration: Not all relationships deteriorate, but those that do tend to show signs of trouble. Boredom, resentment, and dissatisfaction may occur. Individuals may communicate less and avoid self-disclosure. Loss of trust and betrayals may take place as the downward spiral continues, eventually ending the relationship. Alternately, the participants may find some way to resolve the problems and reestablish trust.
5. Termination: The final stage marks the end of the relationship, either by breakup, death, or spatial separation and severing all existing ties of either friendship or romantic love.

Knapp's Theory of Relational Development

Another theory, developed by M. L. Knapp, is known as the model of relational development. This theory consists of two main stages, each with several parts. The first stage is known as the coming together phase, and the second stage is known as the coming apart phase.

Coming Together

Coming together consists of five phases—initiating, experimentation, intensifying, integration, and bonding. 

1. During initiating, first impressions are made; physical factors play a large role in this phase. People often want to portray themselves as easy to talk to, friendly, and open to discussion. This phase tends to be superficial as people are trying to make a good first impression. 
2. During experimentation, the two people attempt to find some common ground between each other's lives, such as common interests and hobbies. People start to open up more and ask more personal questions as they get to know one another. 
3. During the intensifying phase, people open themselves up fully in the hope of being accepted by the potential mate. During this phase, people may reveal secrets about themselves or others in order to test the trust level of potential partners. 
4. The integration phase involves people merging their lives together and solidifying a relationship status. 
5. Finally, during the bonding phase, people recognize a commitment to one another (traditionally through marriage, though many alternative forms of commitment exist) and the relationship lasts until death, breakup, or divorce.

Coming Apart 

Coming apart consists of five stages as well—differentiating, circumscribing, stagnation, avoidance, and termination. 

1. Differentiation involves focusing more on differences rather than similarities. This can lead to an increasing emotional distance between the parties involved. 
2. During circumscribing, the primary focus of the relationship shifts from differences to setting limits and boundaries on communication between the two people. This further pushes two people apart. 
3. Stagnation is when two people have reached a "stand-off" phase—nothing changes and neither party is willing to change. 
4. Avoidance occurs when people engage in limited communication and take steps to distance themselves from one another. 
5. Finally, during termination, the relationship is ended.