Sometimes we want to see how people change over time, as in studies of human development and lifespan. When we test the same group of individuals repeatedly over an extended period of time, we are conducting longitudinal research. Longitudinal research is a research design in which data-gathering is administered repeatedly over an extended period of time. For example, we may survey a group of individuals about their dietary habits at age 20, retest them a decade later at age 30, and then again...

Longitudinal studies are also widely used in other medical and social science fields. For instance, in cardiovascular research, they can monitor patients' health over decades to identify risk factors for heart disease, such as high cholesterol or smoking, and evaluate the long-term effectiveness of preventive measures. Similarly, in mental health studies, researchers might follow individuals from adolescence into adulthood to understand the development and progression of conditions like...

Adopting a healthier lifestyle often requires overcoming significant challenges, but leveraging psychological, social, and cultural resources can facilitate meaningful change. Effective self-change hinges on understanding and applying key tools such as motivation and goal setting, which help sustain efforts toward long-term health benefits.
Motivation and Self-Determination
Motivation, the driving force behind behavior, plays a pivotal role at every stage of the change process. The research...

In cross-sectional research, a researcher compares multiple segments of the population at the same time. If they were interested in people's dietary habits, the researcher might directly compare different groups of people by age. Instead of following a group of people for 20 years to see how their dietary habits changed from decade to decade, the researcher would study a group of 20-year-old individuals and compare them to a group of 30-year-old individuals and a group of 40-year-old...

Erik Erikson, a stage theorist, adapted Freud's theory to emphasize social factors in personality development throughout life, a concept known as psychosocial development. Unlike Freud, who focused on early childhood, Erikson believed that personality evolves across eight life stages, each marked by a specific challenge or "crisis." Successful resolution of each stage fosters competence, while failure may lead to feelings of inadequacy.
The first four of Erikson's eight...

Developmental psychology explores the changes and continuities in human abilities throughout life, encompassing physical, cognitive, linguistic, and social dimensions. Human development is not restricted to growth, but includes aspects of decline, particularly in physical abilities as individuals age. Developmental psychologists seek to understand how people change as they age and how their mental and social skills evolve.
Developmental Milestones
A key concept in developmental psychology is...