Developmental psychologists study how humans change and grow from conception through childhood, adolescence, adulthood, and death. They view development as a lifelong process that can be studied scientifically across three developmental domains—physical, cognitive, and psychosocial development. 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.

There are several theories of development that focus on the following issues: whether development is continuous or discontinuous, whether development follows one course or many, and the relative influence of nature versus nurture on development.

Continuous vs. Discontinuous Development

The continuous-development perspective views development as a cumulative process, gradually improving on existing skills. With this type of development, there is gradual change—such as a child growing slightly taller each year. In contrast, theorists who view development as discontinuous believe that development takes place in unique stages: it occurs at specific times or ages. With this type of development, the change is more sudden, such as an infant’s ability to conceive object permanence.

Continuous vs. discontinuous development

The concept of continuous development can be visualized as a smooth slope of progression, whereas discontinuous development sees growth in more discrete stages.

Nature vs. Nurture

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, and is a central question in developmental psychology. 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.  

Theories of Development

There are many theories regarding how babies and children grow and develop into happy, healthy adults: 

• Sigmund Freud suggested that we pass through a series of psychosexual stages in which our energy is focused on certain erogenous zones on the body. 
• Eric Erikson modified Freud’s ideas and suggested a theory of psychosocial development: he said that our social interactions and successful completion of social tasks shape our sense of self. 
• Jean Piaget proposed a theory of cognitive development that explains how children think and reason as they move through various stages. 
• Lawrence Kohlberg turned his attention to moral development: he said that we pass through three levels of moral thinking that build on our cognitive development.