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Psychology · Foundations

What Psychology Studies

9 min read 5 practice questions
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On this page 9 sections
  1. In 30 seconds
  2. Why this matters
  3. The college version
  4. Eli explains
  5. Worked example
  6. Key takeaway
  7. Quick check
  8. Study tools
  9. Sources & references

In 30 seconds

is the scientific study of the and . The mind is inner experience — thoughts, feelings, memories — and behavior is what people observably do. Psychologists study both, across subfields from clinical and cognitive to developmental, social, and biological psychology. What makes the field a science: psychologists test ideas with evidence instead of trusting intuition, authority, or popular claims. Checking claims against data is what separates research psychology from pop psychology.

Why this matters

Everyone has a mind, and everyone watches other people behave, so psychology’s subject feels familiar — and casual answers feel trustworthy. But folk sayings contradict each other: birds of a feather flock together, yet opposites attract. Psychology exists because intuition is not evidence. Its tested findings explain real things: why memories distort, why people go along with a crowd, why sleep shapes learning. The habits the field teaches — asking answerable questions, demanding evidence, weighing competing results — transfer to any career. And knowing how research works helps anyone tell a supported finding from a self-help slogan dressed up as science.

The college version

What psychology is

Psychology is the scientific study of the mind and behavior. That is the working definition used by the American Psychological Association (APA) and the one this course builds on. Two parts matter. First, psychology is a science: it gathers knowledge through systematic observation, experimentation, and analysis, not through intuition, tradition, or authority alone. Second, its subject includes both the mind and behavior — the inner world and the outer action. The APA’s dictionary describes psychology as a discipline that emerged from philosophy into an science. OpenStax’s Psychology 2e agrees: psychology refers to the scientific study of the mind and behavior, and psychologists use the scientific method to acquire knowledge. Before the late 1800s, questions about the mind belonged to philosophy; only then did psychology become its own academic discipline. Because behavior is rooted in biology, parts of psychology work like a natural science, and because people are shaped by interactions with others, psychology is also a social science.

Mind and behavior — two sides of one subject

The mind is the inner side of the subject: thoughts, feelings, perceptions, memories, and attention — experience that only the person having it can access directly. The APA dictionary defines mind broadly as all the intellectual and psychological phenomena of an organism, and more narrowly as cognitive activities such as perceiving, attending, thinking, problem solving, language, learning, and memory. Behavior is the observable side: an organism’s activities in response to internal or external stimuli — what a person does that others can see, hear, or measure. Original example: Maya is waiting for exam results. Her racing thoughts, her mental replay of the questions she left blank, and the flutter in her chest are mind. Her pacing, the way she refreshes the results page, and the exhale when it finally loads are behavior. Psychologists study both sides and the connection between them: how a thought becomes an action, and how an action reshapes a thought.

What psychologists do

Psychologists work in three broad ways, and many do more than one. Researchers design studies, collect and analyze data, and publish findings, in universities, hospitals, research institutes, and companies. Teachers bring the field to students: professors build courses, supervise projects, and train the next generation. Practitioners apply psychological knowledge directly — clinical and counseling psychologists work with individuals and families, industrial–organizational psychologists advise workplaces, and school and sports psychologists serve specific settings. The same training grounds all three paths; the difference is whether a psychologist produces knowledge, passes it on, or puts it to work.

Five major subfields

Modern psychology divides into subfields, each with its own questions. focuses on diagnosing and treating psychological disorders and other problematic patterns of behavior — for example, a psychologist in a community clinic helping a client work up to returning to crowded places. studies thoughts and mental processes and how they relate to experience and action — for example, a researcher testing whether drivers on a hands-free call notice fewer road signs. is the scientific study of change across the lifespan — for example, tracking how a toddler’s vocabulary grows between eighteen and twenty-four months. focuses on how people interact with and relate to others — for example, studying why an audience is more likely to applaud when the people around them start clapping. Biological psychology explores how biology, especially the nervous system, influences behavior — for example, measuring how stress hormones rise in people about to give a speech. Each subfield is its own territory; this lesson only maps the borders.

The science idea: testing ideas with evidence

The core scientific idea is simple: claims about mind and behavior must be tested with evidence. A researcher turns a vague belief into a testable question, gathers observations, and lets the results support or weaken the idea. Original example: folk wisdom says gloomy weather makes people gloomy. That claim is testable — a researcher could ask volunteers to rate their mood daily for a month, record the weather, and compare the two. Whatever the outcome, the claim has met evidence. Contrast an untestable claim: “your energy field is unbalanced.” Nothing observable corresponds to an energy field, so no evidence can support or refute it, and science has nothing to say about it. Science works with what is perceivable and measurable. That limit applies to psychology too: some inner experience is not yet directly measurable, which is why findings are careful, probabilistic statements about groups rather than certainties about individuals. How those tests are designed is the scientific method’s territory, not this lesson’s.

Pop psychology versus research — the honest framing

Not everything labeled psychology is psychology. Pop psychology — self-help bestsellers, magazine quizzes, viral personality claims — sometimes restates real research and sometimes invents it. The difference is evidence. A research finding has survived a study with a clear question and a measured outcome, usually peer review, and often replication by other labs. A pop claim may rest on one dramatic anecdote. Original example: a viral article announces that left-handed people are more creative. No definition of creativity, no comparison group, no measure — so it is a claim about the world, not yet a finding about it. The honest framing: psychology is a science with a human face. It is rigorous about evidence and humble about certainty. Findings describe tendencies in groups, not fortunes for individuals; effects are real but often modest; and the field corrects itself as better evidence arrives. Science applied to the most human of subjects — that is what psychology studies.

Eli, the EliExplains learning guide

Eli explains

The same idea, in plain words

Explain it like I’m 10

Psychology is the science of what happens inside your head and what you do because of it. The inside part — thoughts, feelings, memories, attention — is the mind. The outside part, the stuff other people can see you do, is behavior. Psychologists study both and how they connect. The key habit that makes it a science: psychologists do not just guess. They take a claim like “gloomy weather makes people gloomy” and turn it into a question they can actually test with real observations, then let the observations decide. That is the whole difference between a science and a collection of opinions.

Picture it like this

Think of psychology as the study of a locked building. The mind is the interior — no one can see it directly. But the building gives itself away at the windows: lights switching on, deliveries arriving, people coming and going. Behavior is what is observable from the street. Psychologists are the researchers camped outside, noting patterns, running experiments on what changes the building’s activity, and building careful theories about the unseen interior — always checking their guesses against what they can actually observe.

Where the picture stops working

A building does not change its behavior because it knows it is being watched, but people do: knowing you are in a study changes how you act, which is why psychology has careful rules for research ethics. A building also has no history of being studied by other buildings; psychologists are humans studying humans, which brings insight and bias at the same time. And unlike identical buildings, every mind is different, so findings describe groups and tendencies — not a blueprint for any one person.

Worked example

Priya’s professor asks the class why their friend Leo seems nervous before presentations. A pop-psychology headline might call it “low self-esteem” and stop there. A psychologist separates the observation into mind and behavior: Leo’s inner experience — racing thoughts, dread, imagining the audience judging him — is mind; his fidgeting, faster speech, and glances at the door are behavior. The class then turns a guess into a testable idea: Leo fidgets more when the audience grows. Testing it would mean counting fidgets while varying audience size and holding everything else steady — an experiment, which is the next topic’s territory. The lesson’s point: name the inner state, watch what people actually do, and turn a guess into a question evidence can answer. That is how psychology works.

Key takeaway

Psychology is the scientific study of the mind and behavior: it names inner experience, watches what people actually do, and — above all — tests its ideas with evidence, so a claim earns belief only when research supports it.

Quick check

3 questions here, of 5 in this lesson’s practice set. Answers stay hidden until you check.

Question 1 of 3foundational

According to the APA working definition used in this lesson, psychology is the scientific study of —

Choose an answer, then check it.
Question 2 of 3intermediate

Which scenario illustrates the difference between the mind and behavior?

Choose an answer, then check it.
Question 3 of 3intermediate

A researcher measures how quickly 5-year-olds and 9-year-olds sort cards by shape, to see how mental abilities change with age. Which subfield’s territory does this work belong to?

Choose an answer, then check it.
Practice all 5

Keep learning

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Practice this lesson
Study tools & related lessonsYou’ll learn to · Common mistakes · Easily confused · Key vocabulary · Related

You’ll learn to

  • Define psychology as the scientific study of the mind and behavior, using the APA working definition.
  • Distinguish the mind, as inner experience, from behavior, as observable action, using original examples.
  • Describe the three main kinds of work psychologists do: research, teaching, and applied practice.
  • Identify five major subfields — clinical, cognitive, developmental, social, and biological psychology — and state what each investigates.
  • Explain why psychology is a science: its ideas are tested with evidence rather than accepted on authority.
  • Analyze the difference between pop psychology claims and research-backed findings.

Common mistakes

  • “Psychology is just common sense.”

    If intuition were enough, contradictory folk sayings — birds of a feather flock together versus opposites attract — could both be right. Psychology exists because intuition is not evidence: its claims must survive systematic observation, and research sometimes shows the opposite of what people expect.

  • “Psychologists only study behavior, because the mind can’t be observed.”

    Psychology studies both. The mind is studied indirectly through measurable indicators — what people report, how fast they respond, what their brains do — and behavior is the observable side of the same subject.

  • “Every psychologist is a therapist.”

    Clinical practice is one subfield. Many psychologists are researchers or teachers, and applied work spans workplaces, schools, sports, and health settings — not only therapy offices.

  • “One study proves it.”

    A single study is one piece of evidence. Findings gain strength when other labs replicate them and when many studies converge; pop-psychology headlines often rest on a single unreplicated study.

  • “Psychology is only about mental illness.”

    Clinical psychology is one branch. Most psychological research concerns everyday minds: how babies learn language, how memory works, how groups make decisions, how sleep affects thinking.

Easily confused

Mind vs. Behavior

The mind is inner experience — thoughts, feelings, memories — visible only to the person having it; behavior is observable action, visible to others. Psychology studies both, and the connection between them.

Research vs. Applied practice

Researchers produce knowledge by designing studies and analyzing data; practitioners apply that knowledge in real settings — a clinic, a school, a workplace. Many psychologists do both across a career.

Psychology vs. Pop psychology

Research psychology tests claims with systematic evidence, peer review, and replication; pop psychology offers catchy claims that may rest on anecdotes or a single unreported study. The evidence behind the claim is what separates them.

Key vocabulary

psychology
The scientific study of the mind and behavior, per the American Psychological Association’s working definition.
mind
The inner side of experience — thoughts, feelings, perceptions, memories, and attention — which only the person having it can access directly.
behavior
An organism’s activities in response to internal or external stimuli, including actions others can observe or measure.
empirical
Based on systematic observation and measurement rather than on intuition, tradition, or authority alone.
hypothesis
A tentative, testable prediction about how things relate, which research can support or fail to support.
clinical psychology
The subfield focused on diagnosing and treating psychological disorders and other problematic patterns of behavior.
cognitive psychology
The subfield that studies thoughts and mental processes and how they relate to experience and action.
developmental psychology
The subfield that studies how people change physically, cognitively, and socially across the lifespan.
social psychology
The subfield that studies how people interact with, influence, and relate to others.
biopsychology
The subfield that studies how biology, especially the nervous system, influences behavior.

Sources & references

  1. APA Dictionary of Psychology — Psychology — American Psychological Association
  2. APA Dictionary of Psychology — Mind — American Psychological Association
  3. APA Dictionary of Psychology — Behavior — American Psychological Association
  4. OpenStax Psychology 2e, Section 1.1: What Is Psychology? — OpenStax, Rice University
  5. OpenStax Psychology 2e, Section 1.3: Contemporary Psychology — OpenStax, Rice University
  6. Simply Psychology — What Is Psychology? — Simply Psychology (Saul McLeod)

EliExplains lessons are original prose written from the open, credible references above. See Copyright & Licensing.

Researched 2026-08-22

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