What you’ll learn to do: define human development and identify the stages of human development

What aspects of ourselves change and develop as we journey through life? We move through significant physical, cognitive, and psychosocial changes throughout our lives—do these changes happen in a systematic way, and to everyone? How much is due to genetics and how much is due to environmental influences and experiences (both within our personal control and beyond)? Is there just one course of development or are there many different courses of development? In this module, we’ll examine these questions and learn about the major stages of development and what kind of developmental tasks and transitions we might expect along the way.

Defining Human Development

Human development refers to the physical, cognitive, and psychosocial development of humans throughout the lifespan. What types of development are involved in each of these three domains, or areas, of life? Physical development involves growth and changes in the body and brain, the senses, motor skills, and health and wellness. Cognitive development involves learning, attention, memory, language, thinking, reasoning, and creativity. Psychosocial development involves emotions, personality, and social relationships.

Psychosocial Domain

Who Studies Human Development and Why?

Many academic disciplines contribute to the study of development and this type of course is offered in some schools as psychology (particularly as developmental psychology); in other schools, it is taught under sociology, human development, or family studies. This multidisciplinary course is made up of contributions from researchers in the areas of health care, anthropology, nutrition, child development, biology, gerontology, psychology, and sociology, among others. Consequently, the stories provided are rich and well-rounded and the theories and findings can be part of a collaborative effort to understand human lives.

The main goals of those involved in studying human development are to describe and explain changes. Throughout this course, we will describe observations during development, then examine how theories provide explanations for why these changes occur. For example, you may observe two-year-old children to be particularly temperamental, and researchers offer theories to explain why that is. We’ll learn a lot more about theories, especially developmental theories, in the next module.

Key Issues in Human Development

There are many different theoretical approaches regarding human development. As we evaluate them in this course, recall that human development focuses on how people change, and the approaches address the nature of change in different ways: 

• Is the change smooth or uneven (continuous versus discontinuous)?
• Is this pattern of change the same for everyone, or are there different patterns of change (one course of development versus many courses)?
• How do genetics and environment interact to influence development (nature versus nurture)?

Is Development Continuous or Discontinuous?

Continuous development views development as a cumulative process, gradually improving on existing skills (Figure 2). With this type of development, there is a gradual change. Consider, for example, a child’s physical growth: adding inches to their height year by year. In contrast, theorists who view development as discontinuous believe that development takes place in unique stages and that it occurs at specific times or ages. With this type of development, the change is more sudden, such as an infant’s ability to demonstrate awareness of object permanence (which is a cognitive skill that develops toward the end of infancy, according to Piaget’s cognitive theory—more on that theory in the next module).

Is There One Course of Development or Many?

Is development essentially the same, or universal, for all children (i.e., there is one course of development) or does development follow a different course for each child, depending on the child’s specific genetics and environment (i.e., there are many courses of development)? Do people across the world share more similarities or more differences in their development? How much do culture and genetics influence a child’s behavior?

Stage theories hold that the sequence of development is universal. For example, in cross-cultural studies of language development, children from around the world reach language milestones in a similar sequence (Gleitman & Newport, 1995). Infants in all cultures coo before they babble. They begin babbling at about the same age and utter their first word around 12 months old. Yet we live in diverse contexts that have a unique effect on each of us. For example, researchers once believed that motor development followed one course for all children regardless of culture. However, childcare practices vary by culture, and different practices have been found to accelerate or inhibit the achievement of developmental milestones such as sitting, crawling, and walking (Karasik, Adolph, Tamis-LeMonda, & Bornstein, 2010).

For instance, let’s look at the Aché society in Paraguay. They spend a significant amount of time foraging in forests. While foraging, Aché mothers carry their young children, rarely putting them down in order to protect them from getting hurt in the forest. Consequently, their children walk much later: They walk around 23–25 months old, in comparison to infants in Western cultures who begin to walk around 12 months old. However, as Aché children become older, they are allowed more freedom to move about, and by about age 9, their motor skills surpass those of U.S. children of the same age: Aché children are able to climb trees up to 25 feet tall and use machetes to chop their way through the forest (Kaplan & Dove, 1987). As you can see, our development is influenced by multiple contexts, so the timing of basic motor functions may vary across cultures. However, the functions are present in all societies.

How Do Nature and Nurture Influence Development?

Are we who we are because of nature (biology and genetics), or are we who we are because of nurture (our environment and culture)? This longstanding question is known in psychology as the nature versus nurture debate. It seeks to understand how our personalities and traits are the product of our genetic makeup and biological factors, and how they are shaped by our environment, including our parents, peers, and culture. For instance, why do biological children sometimes act like their parents—is it because of genetics or because of early childhood environment and what the child has learned from their parents? What about children who are adopted—are they more like their biological families or more like their adoptive families? And how can siblings from the same family be so different?

We are all born with specific genetic traits inherited from our parents, such as eye color, height, and certain personality traits. Beyond our basic genotype, however, there is a deep interaction between our genes and our environment. Our unique experiences in our environment influence whether and how particular traits are expressed, and at the same time, our genes influence how we interact with our environment (Diamond, 2009; Lobo, 2008). There is a reciprocal interaction between nature and nurture as they both shape who we become, but the debate continues as to the relative contributions of each.

Try It

Periods of Human Development

Think about the lifespan and make a list of what you would consider the basic periods of development. 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:

1. Prenatal Development
2. Infancy and Toddlerhood
3. Early Childhood
4. Middle Childhood
5. Adolescence
6. Early Adulthood
7. Middle Adulthood
8. Late Adulthood

In addition, the topic of “Death and Dying” is usually addressed after late adulthood since overall, the likelihood of dying increases in later life (though individual and group variations exist). Death and dying will be the topic of our last module, though it is not necessarily a stage of development that occurs at a particular age.

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 discover the distinctions between being 28 or 48 as well. But first, here is a brief overview of the stages.

Prenatal Development

Conception occurs and development begins. There are three stages of prenatal development: germinal, embryonic, and fetal periods. All of the major structures of the body are forming and the health of the mother is of primary concern. There are various approaches to labor, delivery, and childbirth, with potential complications of pregnancy and delivery, as well as risks and complications with newborns, but also advances in tests, technology, and medicine. The influences of nature (e.g., genetics) and nurture (e.g., nutrition and teratogens, which are environmental factors during pregnancy that can lead to birth defects) are evident. Evolutionary psychology, along with studies of twins and adoptions, help us understand the interplay of factors and the relative influences of nature and nurture on human development.

Infancy and Toddlerhood

The first year and a half to two years of life are ones of dramatic growth and change. A newborn, with many involuntary reflexes and a keen sense of hearing but poor vision, is transformed into a walking, talking toddler within a relatively short period of time. 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. Interactions with primary caregivers (and others) undergo changes influenced by possible separation anxiety and the development of attachment styles. Social and cultural issues center around breastfeeding or formula-feeding, sleeping in cribs or in the bed with parents, toilet training, and whether or not to get vaccinations.

Early Childhood

Early childhood is also referred to as the preschool years, consisting of the years that follow toddlerhood and precede formal schooling, roughly from around ages 2 to 5 or 6. 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. This knowledge does not come quickly, however, and preschoolers may initially have interesting 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. 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.

Middle Childhood

The ages of 6-11 comprise middle childhood and much of what children experience at this age is connected to their involvement in the early grades of school. Now the world becomes one of learning and testing new academic skills and assessing one’s abilities and accomplishments by making comparisons between self and others. Schools participate in this process by comparing students and making these comparisons public through team sports, test scores, and other forms of recognition. The brain reaches its adult size around age seven, but it continues to develop. Growth rates slow down and children are able to refine their motor skills at this point in life. Children also begin to learn about social relationships beyond the family through interaction with friends and fellow students; same-sex friendships are particularly salient during this period.

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. Ironically, adolescents have a sense of invincibility that puts them at greater risk of dying from accidents or contracting sexually transmitted infections that can have lifelong consequences. 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.

Early 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!). It is a time when we are at our physiological peak but are most at risk for involvement in violent crimes and substance abuse. 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. 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 late thirties (or age 40) through the mid-60s are referred to 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. 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). 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, many factors are involved and a better way to appreciate the diversity of older adults is to go beyond chronological age and examine whether a person is experiencing optimal aging (like the gentleman pictured in Figure 8 who is in very good health for his age and continues to have an active, stimulating life), normal aging (in which the changes are similar to most of those of the same age), or impaired aging (referring to someone who has more physical challenge and disease than others of the same age).

Death and Dying

The study of death and dying is seldom given the amount of coverage it deserves. Of course, there is a certain discomfort in thinking about death, but there is also a certain confidence and acceptance that can come from studying death and dying. Factors such as age, religion, and culture play important roles in attitudes and approaches to death and dying. There are different types of death: physiological, psychological, and social. The most common causes of death vary with age, gender, race, culture, and time in history. Dying and grieving are processes and may share certain stages of reactions to loss. There are interesting examples of cultural variations in death rituals, mourning, and grief. The concept of a “good death” is described as including personal choices and the involvement of loved ones throughout the process. Palliative care is an approach to maintain dying individuals’ comfort level, and hospice is a movement and practice that involves professional and volunteer care and loved ones. Controversy surrounds euthanasia (helping a person fulfill their wish to die)—active and passive types, as well as physician-assisted suicide, and legality varies within the United States.