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How many periods or stages are on your list? Perhaps you have three: childhood, adulthood, and old age. Or maybe four: infancy, childhood, adolescence, and adulthood. Developmentalists often break the lifespan into eight stages.
The list of the periods of development reflects unique aspects of the various stages of childhood and adulthood that will be explored in this book, including physical, cognitive, and psychosocial changes. So while both an 8-month-old and an 8-year-old are considered children, they have very different motor abilities, cognitive skills, and social relationships. Their nutritional needs are different, and their primary psychological concerns are also distinctive. The same is true of an 18-year-old and an 80-year-old, both considered adults. We will also learn about the differences between being 28 and 48.
But first, a brief synopsis of the stages is provided here. Delivery, as well as risks and complications with newborns, but also advances in tests, technology, and medicine. There are obvious influences from nature (such as genetics) and nurture (such as nutrition and teratogens, which are environmental factors that can cause birth defects during pregnancy). The study of twins and adoptions, evolutionary psychology, and other related fields help us comprehend how factors interact with one another and how nature and nurture affect human development in different ways.
Infancy And Toddlerhood
The first year and a half to two years of life are ones of dramatic growth and change. In a relatively short amount of time, a newborn with many involuntary reflexes, a keen sense of hearing, and poor vision transforms into a walking, talking toddler (Figure 2).
Caregivers similarly transform their roles from those who manage feeding and sleep schedules to constantly moving guides and safety inspectors for mobile, energetic children. Brain development happens at a remarkable rate, as does physical growth and language development. Infants have their own temperaments and approaches to play. Possible separation anxiety and the development of attachment styles influence changes in interactions with primary caregivers and others.
Breastfeeding or formula feeding, sleeping in a crib or with parents, toilet training, and whether or not to get vaccinated are all social and cultural issues.
Early Childhood
The years that follow toddlerhood and precede formal education are referred to as early childhood (also referred to as the preschool years) (Figure 3).
As a preschooler, the child is busy learning language (with amazing growth in vocabulary), is gaining a sense of self and greater independence, and is beginning to learn the workings of the physical world. Preschoolers may initially have intriguing conceptions of size, time, space, and distance, such as demonstrating how long something will take by holding out their two index fingers several inches apart.
However, this knowledge does not come quickly. A toddler’s fierce determination to do something may give way to a four-year-old’s sense of guilt for doing something that brings the disapproval of others.
Adolescence
Adolescence is a period of dramatic physical change marked by an overall physical growth spurt and sexual maturation, known as puberty; timing may vary by gender, cohort, and culture.
It is also a time of cognitive change as the adolescent begins to think of new possibilities and to consider abstract concepts such as love, fear, and freedom (Figure 5). Ironically, adolescents’ sense of invincibility increases their vulnerability to accidents and sexually transmitted infections, both of which can have long-term effects.
Research on brain development helps us understand teen risk-taking and impulsive behavior. A major developmental task during adolescence involves establishing one’s own identity. Teens typically struggle to become more independent from their parents. Peers become more important, as teens strive for a sense of belonging and acceptance; mixed-sex peer groups become more common.
New roles and responsibilities are explored, which may involve dating, driving, taking on a part-time job, and planning for future academics.
Young Adulthood
Late teens, twenties, and thirties are often thought of as early adulthood (students who are in their mid to late 30s may love to hear that they are young adults!).
We are at our most physiologically active during this time, but we are also most vulnerable to involvement in drug and violent crime. It is a time of focusing on the future and putting a lot of energy into making choices that will help one earn the status of a full adult in the eyes of others (Figure 6). Love and work are the primary concerns at this stage of life.
In recent decades, it has been noted (in the U.S. and other developed countries) that young adults are taking longer to “grow up.” They are waiting longer to move out of their parents’ homes, finish their formal education, take on work/careers, get married, and have children.
One psychologist, Jeffrey Arnett, has proposed that there is a new stage of development after adolescence and before early adulthood, called “emerging adulthood,” from 18 to 25 (or even 29) when individuals are still exploring their identities and don’t quite feel like adults yet. Cohort, culture, time in history, the economy, and socioeconomic status may be key factors in when youth take on adult roles.
Middle Adulthood
The period from the late thirties (or age 40) to the middle of one’s sixties is known as middle adulthood.
This is a period in which physiological aging that began earlier becomes more noticeable and a period at which many people are at their peak of productivity in love and work. It may be a period of gaining expertise in certain fields and being able to understand problems and find solutions with greater efficiency than before.
It can also be a time of becoming more realistic about possibilities in life; of recognizing the difference between what is possible and what is likely (Figure 7). Referred to as the sandwich generation, middle-aged adults may be in the middle of taking care of their children and also taking care of their aging parents.
While caring about others and the future, middle-aged adults may also be questioning their own mortality, goals, and commitments, though not necessarily experiencing a “mid-life crisis.”
Late Adulthood
This period of the lifespan, late adulthood, has increased in the last 100 years, particularly in industrialized countries, as average life expectancy has increased.
Late adulthood covers a wide age range with a lot of variation, so it is helpful to divide it into categories such as the “young-old” (65-74 years old), “old-old” (75-84 years old), and “oldest-old” (85+ years old; Figure 8).
The young-old are similar to middle-aged adults; possibly still working, married, relatively healthy, and active. The old-old have some health problems and challenges with daily living activities; the oldest-old are often frail and in need of long term care.
However, there are a lot of factors at play, and a better way to appreciate the variety of older adults is to look beyond a person’s chronological age to see if they are experiencing optimal aging (like the man in Figure 8, who is in excellent health for his age and continues to lead an active, stimulating life).
