What Is Psychology?

The short answer

Psychology is the scientific study of the mind and behavior. It explores how we think, feel, perceive, learn and act, as individuals and in groups. Psychologists use scientific methods to study everything from brain function and memory to child development, relationships and mental health.

Put simply, psychology asks why people do what they do, and then tests the answers with evidence rather than relying on intuition. The field spans pure research (for example, how memory works) and practical application (for example, helping someone cope with anxiety or designing a safer cockpit). For a shorter version, see our psychology definition page.

Etymology: the word's origins

The word "psychology" comes from two Greek roots: psyche (ψυχή), meaning "breath," "soul" or "mind," and logos (λόγος), meaning "study" or "account." Literally, psychology means "study of the soul" or "study of the mind."

In Greek myth, Psyche was a mortal woman who became immortal after a series of trials, and she was often taken as a symbol of the human soul. The Latin form psychologia appeared in the 16th century in the writing of scholars such as Marko Marulić and Rudolf Goclenius, and the German philosopher Christian Wolff popularized it in the 1730s. The word entered English over the following centuries, but psychology as an independent science did not emerge until the late 1800s.

The formal definition

The American Psychological Association (APA) defines psychology as the study of the mind and behavior. Textbook definitions add that it is scientific. Three elements matter:

1. Scientific study: psychology relies on empirical methods such as controlled experiments, systematic observation and statistical analysis rather than intuition or speculation.
2. Behavior: observable actions, from simple reflexes to complex social interactions.
3. Mental processes: internal experiences such as thoughts, emotions, memories and perceptions, which cannot be observed directly and must be inferred from behavior, self-report or brain measures.

Psychology studies typical and atypical functioning, individuals and groups, and humans and other animals. Its four classic goals are to describe, explain, predict and change behavior and mental processes. That broad scope makes psychology relevant to almost every part of life, from parenting and education to work, health and law.

A brief history of psychology

Ancient and philosophical roots

Questions about the mind are ancient. Greek philosophers such as Plato and Aristotle asked how we perceive, remember and reason. The medieval scholar Ibn al-Haytham studied visual perception and optical illusions. In the 17th century René Descartes argued for mind-body dualism, while British empiricists such as John Locke proposed that knowledge comes from experience. These debates, including the long-running nature vs. nurture question, set the agenda for later science.

Birth of scientific psychology (1879)

Wilhelm Wundt established the first dedicated psychology laboratory at the University of Leipzig in 1879, the date usually given for psychology's birth as an independent science. Wundt used trained, controlled introspection alongside reaction-time measurements. His student Edward Titchener developed structuralism in the United States, which tried to break conscious experience into basic elements. William James championed functionalism, asking what mental processes are for and how they help us adapt.

Major schools of thought

The early 20th century saw competing schools:

• Gestalt psychology (Max Wertheimer, Wolfgang Köhler, Kurt Koffka) argued that the mind perceives organized wholes rather than separate pieces, summed up as "the whole is different from the sum of its parts." Its principles of perceptual organization, such as proximity and similarity, are still taught today.
• Psychoanalysis (Sigmund Freud) emphasized unconscious drives, childhood experience and defense mechanisms, such as sublimation, in which unacceptable impulses are redirected into socially valued activities like art or sport.
• Behaviorism (John B. Watson, B. F. Skinner) restricted psychology to observable behavior and how it is learned through conditioning.
• Humanistic psychology (Carl Rogers, Abraham Maslow) stressed free will, personal growth and self-actualization, and became known as the "third force" after psychoanalysis and behaviorism.
• Cognitive psychology emerged in the 1950s and 1960s, treating the mind as an information processor and bringing memory, attention, language and problem solving back to center stage. Ulric Neisser's 1967 book Cognitive Psychology gave the field its name.

Each school contributed lasting insights, and modern psychology generally integrates several perspectives rather than following one. Our psychology timeline covers these developments in more detail.

Modern psychology (1990s to present)

Today's psychology is increasingly interdisciplinary. Neuroscience and brain imaging link behavior to brain activity. Evolutionary psychology asks how natural selection shaped the mind. Cross-cultural psychology tests whether findings hold beyond Western, educated, industrialized, rich and democratic (WEIRD) samples. Positive psychology studies well-being and strengths. After the 2015 Open Science Collaboration found that many published results replicated with smaller effects, or not at all, the field adopted reforms such as preregistration, open data and large multi-lab studies.

Major perspectives in psychology

A perspective is a lens for explaining behavior. The same behavior, such as a student's test anxiety, can be explained in several complementary ways.

Biological perspective

Examines how genetics, brain structures, neurotransmitters and hormones influence behavior, from the brain regions involved in memory to the role of genes and environment in personality.

Behavioral perspective

Focuses on behavior learned through classical conditioning, operant conditioning and observation. It is widely applied in education, parenting and behavior therapy.

Cognitive perspective

Studies mental processes such as attention, memory, language, reasoning and decision making. It underpins much of modern therapy (for example, cognitive behavioral therapy) and has influenced artificial intelligence research.

Humanistic perspective

Emphasizes personal growth, self-actualization and free will, and focuses on human potential rather than dysfunction. Rogers's person-centered therapy grew from this tradition.

Psychodynamic perspective

Explores unconscious processes, early experiences and inner conflicts. Modern psychodynamic approaches have moved away from many of Freud's specific claims and integrate attachment research and empirical testing.

Evolutionary perspective

Asks how natural selection shaped psychological traits such as fear, mate preferences and cooperation. Critics caution against "just-so stories" that are hard to test.

Sociocultural perspective

Studies how culture, social roles, norms and relationships shape thought and behavior, and highlights that findings from one culture do not always generalize to others.

How psychologists study the mind

Psychology uses several research methods, each with strengths and limits. Our guide to research methods in psychology covers them in depth.

• Experiments manipulate one variable and measure its effect on another, with random assignment, which allows cause-and-effect conclusions.
• Correlational studies measure how variables relate, such as sleep and grades, but cannot by themselves show causation.
• Naturalistic observation records behavior in everyday settings without intervening.
• Surveys and questionnaires gather self-reported data from large samples, though answers can be shaped by wording and social desirability.
• Case studies examine one person or small group in depth, which is useful for rare conditions but hard to generalize.
• Longitudinal and cross-sectional studies track change over time, or compare age groups at one point.
• Neuroimaging and physiological measures (fMRI, EEG, heart rate) observe the body and brain during psychological tasks.
• Meta-analysis combines results across many studies to estimate an overall effect.

Research is governed by ethical codes such as the APA's Ethical Principles. Studies with people must normally pass review by an ethics committee, obtain informed consent, minimize harm and protect confidentiality. Several famous experiments, including the Milgram obedience studies, helped prompt these rules.

Major branches of psychology

Psychology has diversified into many specialized fields. A useful split is between research branches, which mainly build knowledge, and applied branches, which use it to solve practical problems. In practice the two overlap.

Research and academic branches

• Cognitive psychology studies how people take in, store and use information: attention, perception, memory, language, problem solving and decision making.
• Developmental psychology studies how people change across the lifespan, from infancy and childhood through adolescence to old age, including theories from Jean Piaget and Erik Erikson.
• Social psychology studies how other people influence our thoughts and behavior: conformity, attitudes, prejudice, attraction and group behavior.
• Biological psychology and neuropsychology study the brain and nervous system and how they relate to behavior.
• Personality psychology studies stable differences between people, such as the Big Five traits.
• Experimental psychology is less a topic than an approach: carefully controlled laboratory study of basic processes such as perception and learning.

Applied and clinical branches

• Clinical psychology assesses and treats mental health conditions.
• Counseling psychology focuses on everyday adjustment, relationships and life transitions.
• Forensic psychology applies psychology to legal questions (compare it with clinical work in forensic vs. clinical psychology).
• Health psychology studies how behavior and stress affect physical health.
• Industrial-organizational psychology applies psychology to hiring, leadership, teams and workplace well-being.
• School psychology and educational psychology support learning and student development.
• Sports psychology studies motivation, focus and performance in athletes.

Famous psychologists who shaped the field

A handful of people appear in nearly every introductory course. Our famous psychologists hub profiles many more.

What do psychologists actually do?

Psychologists work in many settings. What they may legally do, such as diagnosing or providing therapy, depends on their training and licensing rules where they practice. For how they compare with other professionals, see psychiatrist vs. psychologist and our overview of mental health professionals.

Clinical practice

Licensed clinical and counseling psychologists assess and treat mental health conditions using evidence-based therapies. They work in hospitals, clinics, community services and private practice with individuals, couples, families and groups.

Research

Research psychologists design and run studies on behavior and mental processes, usually in universities, research institutes, government agencies or industry, including technology companies.

Education

Many psychologists teach at universities and train future practitioners. School and educational psychologists assess learning difficulties and help design support for students.

Consultation

Organizational psychologists advise businesses on selection, training, leadership and workplace culture. Forensic psychologists consult with courts and legal teams, for example on competency evaluations.

Applied settings

Sports psychologists work on motivation and performance. Health psychologists help people manage chronic illness and change health behaviors. User experience researchers apply psychology to product and technology design. Our psychology careers guide covers training routes.

Why psychology matters

Psychological research informs decisions at every scale, from personal habits to public policy.

Personal benefits

Learning psychology can help you understand yourself and others, communicate better, study more effectively (for example, using spaced practice and self-testing), make more careful decisions by knowing common cognitive biases, and build healthier habits.

Societal impact

Psychology contributes to better teaching methods, safer workplaces and product design, efforts to reduce prejudice, evidence-based public health campaigns, more accurate eyewitness procedures in the justice system, and policies that use insights about how people actually behave, such as default options in retirement savings.

Common misconceptions about psychology

"Psychology is just common sense"

Research often contradicts intuition. For example, rewarding people for an activity they already enjoy can sometimes reduce their interest in it (the overjustification effect), and venting anger tends to keep it going rather than release it. Common sense also often contains contradictory sayings ("birds of a feather flock together" vs. "opposites attract"); research tests which holds, and when.

"Psychologists can read minds"

Psychologists study patterns of behavior and use structured assessment tools. They cannot read thoughts or instantly analyze a personality, and good assessment takes time and multiple sources of information.

"Psychology is only about mental illness"

Clinical work is the best-known part of psychology, but most psychological research studies typical functioning: perception, memory, learning, emotion, motivation, relationships, creativity and well-being.

"Therapy is only for serious problems"

People seek psychological support for many reasons, including stress, relationship difficulties, grief, career decisions and life transitions, as well as diagnosable conditions.

Other popular myths, such as the claim that we use only 10% of our brains or that people learn best in their preferred "learning style," are not supported by evidence. Our article on mental health myths covers more.

How to learn more about psychology

Whether you are considering a career or simply curious about the mind, these are good next steps:

1. Start with the psychology basics hub for core concepts.
2. Explore specific branches such as cognitive, developmental or social psychology.
3. Read about landmark experiments and what they did and did not show.
4. Use our study guides or the AP Psychology guide for structured learning.
5. Read psychology book summaries for accessible introductions.
6. Learn about psychology degrees and career paths.

Start your psychology journey

Psychology combines curiosity about human nature with the discipline of scientific testing. It explains why first impressions stick, how children learn language, why groups make poor decisions and what helps people recover from adversity. Wherever your interest starts, the same core idea applies: careful evidence beats assumption when it comes to understanding the mind.