Humans have been around for a very long time. We have learned how to adapt to various environments and form connections with one another in ways that help us develop and thrive as individuals, family units, communities, and societies. We are diverse in our looks, languages, thinking, and expression. As distinct as we are from each other, we also share many commonalities in how our bodies and brains develop over time.

Those studying human development are often interested in understanding the differences and similarities between groups of people. Researchers may see that a child who grows up in the United States displays a similar growth pattern as a child from Brazil. They may also see that two children raised in the same city can have very different outcomes based on the neighborhood they are raised in. Throughout the textbook, we will examine these diverse outcomes influenced by biology and the environment and vice versa. The relationship between a child and the social systems they live in becomes more complex as development occurs.

The first 18 years of life are marked by periods of rapid growth and opportunities for children to learn the skills they need to be successful in their lives. This development is influenced by many factors, such as biology, genetics, history, location, culture, social contexts, and environment. Given the variety of factors that impact us, researchers have found ways to organize and explain periods of growth and development to increase our understanding of what humans need to thrive during the various ages and stages of life.

Figure 1.1. Image depicting human development over time. Photo by Rajiv Perera on Unsplash.

1.2.1 Human Development as an Interdisciplinary Field of Study

Human development is an interdisciplinary social science. Many fields of study contribute to our understanding of how humans grow and change. Human development covers topics that range from physical and biological changes to how we interact with ourselves and others. Human development as a discipline depends on research from more traditional “hard science” disciplines such as biology and chemistry as well as social sciences like sociology, psychology, and anthropology. If a field of study involves people as a subject, it has the potential to deepen our understanding of how humans change and grow. Some disciplines may be more prominent, but many questions in human development can be informed best through an interdisciplinary approach or one that blends the sciences together.

You might wonder, “what kind of jobs actually depend on human development?” Broadly speaking, if a job involves interactions with people, it is likely informed by the field of human development. Jobs that seemingly have nothing to do with human beings, such as computer technology, are interacting with the realities of humans and their needs. Even if a job is not directly related to the human development field, chances are the way that people learn, acquire, and refine skills will be important.

Some industries heavily depend on studying human development, such as the medical field. Medical professionals need to understand how the human body changes and grows. Education is another industry that relies on human development research and theory to provide services to children and adults. For example, teachers rely on the knowledge of cognitive skills to determine best practices in teaching and learning. Human services professionals benefit from research in human development because it provides a better understanding of how social problems affect people and how to design effective interventions.

There is much to learn from studying humans and their development. We can gain an understanding of ourselves and others. We can learn more about how the environment impacts us or how biology and genetics influence us. We can learn how social issues impact people’s development and identify what people need to overcome adverse experiences. Most importantly, we can grow in our awareness and appreciation of the resilience of humans.

1.2.2 Major Domains of Human Development

Growth periods throughout childhood are categorized by developmental domains, which refer to a broad area of development that encompasses a range of skills and abilities. The most common domains found in human development literature include cognitive, language, physical, social, and emotional development. These are important domains for understanding the events and experiences of human development.

Some areas of development, such as language, reflect the dynamic impact domains have on each other. Language development is a set of skills on its own, but social relationships and physical development are important to the ability to form language. Without interpersonal interaction (social and emotional), it would be hard to learn language. The atypical development of the ear canal (physical development) may also impair language skills. Development in one domain may significantly shape the development of another. For this reason, we must be sure to consider how each unique element of development shapes the whole person.

1.2.2.1 Developmental Milestones

Developmental milestones are skills and behaviors used to evaluate developmental progress within a given domain. Domains represent important categories of development across the lifespan, whereas milestones are typically age-driven, meaning they change as the developmental expectations shift with age. We will discuss developmental milestones within each stage and age of development throughout the chapters. Some developmental milestones are witnessed across cultures while others vary based on community values and structures. While we include typical developmental milestones based on Western culture within our textbook, we also recognize that many factors influence when and how children will develop certain skills.

A study in cultural differences highlights that there exists important distinctions in mother-infant interactions, attachment, motor development, development of self identity among cultures (Keller, 2017). For example, children in Western cultures go through formalized schooling during most of their childhood. Formal schooling acts as a specific kind of learning environment which will influence the type of skills a child learns and the timing of when those skills are formed. Children who live in farmer or hunter type communities with limited or no formal schooling, may develop similar skills but through different means (hands-on experience) or may develop skills at a later time which would shift our understanding of expected developmental milestones based on age.

1.2.2.2 Cognitive Development

Cognitive development refers to the way children take in and process information, acquire knowledge and skills, and use information to problem solve. It includes growth in intellectual abilities such as critical thinking, reasoning, and understanding, as well as information organization and memory. Cognitive development impacts other developmental domains, such as language and social-emotional development.

1.2.2.3 Language Development

Language development is a process by which children acquire and process language and learn how to use it to communicate with others. Language development is a dynamic process impacted by cognitive, physical, social, and emotional growth.

1.2.2.4 Physical Development

Physical development is a process in which children’s brains and bodies grow to help them thrive in their environment. The body and brain grow from the prenatal stage through early adulthood. Physical development includes skeletal growth, muscle development, coordination, and development of gross and fine motor skills.

1.2.2.5 Social and Emotional Development

Social and emotional development is a process by which children gain understanding of themselves, their emotions, and the connections between themselves and others. These domains focus on changes in self-perception, emotions, and interpersonal relationships, including family, friends, and peer groups. Social and emotional development is impacted by cognitive and language domains since the capacity for complex thinking and information integration is needed to develop and maintain relationships.

1.2.3 Domains Highlighted in This Textbook

Human development literature and research have generally focused on the major developmental domains when describing children’s growth. While these domains encompass important skills and behaviors, they do not give us a full sense of how a child develops into an adult nor do they describe on their own the nuances that influence children in their daily lives. In this textbook, we have expanded the domains to include adaptive, sexual, moral, gender identity, and identity development. We see these areas as equally important in understanding the whole child’s experience, and we also recognize that development in these areas varies widely from child to child.

1.2.3.1 Adaptive Development

Adaptive development is a process by which children learn skills and behaviors that allow them to engage in developmentally appropriate self-care and life tasks. Grooming, feeding, and hygiene routines are common examples of adaptive skills. Some specific examples of adaptive development may traditionally be covered in other domains, such as toilet training as part of physical development.

We are choosing to address adaptive development as its own domain in order to bring attention to the individuality of these skills and how they relate to a child’s development within their social context. We believe this allows a greater exploration on how children thrive in their environments.

1.2.3.2 Sexual Development

Sexual development is a biological and physiological process by which children develop an awareness of their bodies leading to sexual maturation, sexual identity, and awareness of oneself as a sexual being. Sexual development also includes psychological and sociocultural processes that shape the personal experiences and understanding of the self as a sexual person. Gender identity and sexual orientation are important in sexual development, but they are also distinct and will be explored for the complex constructs they are.

In this textbook, we want to highlight sexual development throughout the stages of childhood and discuss how it plays a role in the overall formation of one’s identity. As authors, educators, and human service workers, we believe sexuality is a natural and inherent part of the human experience. So, why isn’t sexual development included as a standard domain in the literature? Based on our experience working in human development fields, we believe this oversight is attributed to several factors:

• The belief that children are not sexual.
• The idea that sexuality is bad and therefore only discussed when necessary.
• A misunderstanding of what sexual development looks like in the early years.

Society often views sexuality as an adult-centered activity. In reality, sexuality is present throughout the lifespan but has distinct features in childhood. Children are sexual, but not in the same way that adults are. In the early years, sexual development is focused on the formation of the sexual organs and a child’s understanding of their body parts and functions. In adolescence, sexual development is related to puberty, hormones, distinct physical body changes, and sometimes sexual activity.

Cultural norms play a significant role in how sexuality is manifested and celebrated in society. In some cultures, there are rites of passage for children that involve changes or alterations to the sexual organs, such as male circumcision or female genital surgery. About a third of the world performs these rituals (Stevens, 2014). In other cultures, topics such as menstruation or masturbation are ignored, shamed, or discussed only when needed.

It is important to acknowledge the role that sexual development plays in a child’s awareness of their bodies, their understanding of consent and physical boundaries, their emotional growth, and the social and romantic relationships they will have as they mature. We believe that all children should be educated about their bodies and that sexuality be managed as a healthy and normal function of development.

1.2.3.3 Moral Development

Moral development occurs as children process their understanding of right and wrong as related to their social and environmental contexts. It develops across the lifespan and can change over time. Increasingly complex cognitive development and diverse social interactions are key to the formation of more advanced moral understanding.

We believe that moral development highly depends on the different bioecological systems a child encounters. As described by theorist Uri Bronfenbrenner, five interrelated ecological systems impact a child’s development, which include:

• microsystem (family, peers)
• mesosystem (interaction between child, family, community)
• exosystem (neighborhood, media)
• macrosystem (wealth, poverty, race)
• chronosystem (major life changes, history)

A child who grows up with an incarcerated parent or lives in an environment with a high crime rate may develop a specific understanding of right and wrong compared to a child who grows up in a safe, wealthy suburb with two parents.

1.2.3.4 Gender Identity Development

Gender identity development refers to one’s innermost understanding of themselves as male, female, neither, or a combination of. The norms and roles of one’s gender are based on biological sex or sex determined at birth. Gender has historically been seen as a binary system (male, female), but we now understand that gender is fluid and exists on a continuum. Children experience gender in various societal systems such as the microsystem, the mesosystem, and the macrosystem.

We learn very early (by at least age 3) about the categories of gender in our culture—that individuals are either “male” or “female” and that elaborate beliefs, behaviors, and meanings are associated with each gender. We can think of this complex set of ideas as a gender ideology or a cultural model of gender. All societies have gender ideologies, just as they have belief systems about other significant areas of life.

1.2.3.5 Identity Development

Identity development refers to a person’s sense of self. Identity is formed in infancy and transforms over the lifespan. Identity development depends on the experiences each person has throughout the developmental domains and the experiences they have within their social and environmental systems.

Theories and research are often centered on the identity development during the adolescent experience. While adolescents go through many changes and refinements about their sense of self, we recognize that a child’s identity formation starts early and is highly dependent on their relationship with their caregivers and home environment. We will discuss identity development throughout the textbook.