A free psychology reference
Psychology is the science of understanding the human mind
Explore every branch, theory, and concept in psychology — from cognitive science and forensic analysis to clinical practice and positive well-being. Written for clarity, backed by research.
Browse by topic
- Psychology BasicsWhat psychology is, its branches, history, research methods and careers.31 guides
- Theories & ConceptsThe big ideas: learning, motivation, development, personality, biases and social influence.64 guides
- Famous PsychologistsThe people who shaped the field, what they found and why it still matters.33 guides
- Landmark ExperimentsThe classic studies, how they were run, what they showed and how they hold up today.23 guides
- Mental Health ConditionsPlain-English overviews of recognised conditions, how they are classified and how they are understood.86 guides
- Feelings & ExperiencesEveryday psychological experiences and thinking patterns, explained.45 guides
- Therapy ApproachesHow the main therapy approaches work, where they came from and what research says.49 guides
- Getting SupportHow mental health care is organised: professionals, costs, insurance and where to start.21 guides
- Wellbeing SkillsEveryday techniques studied in psychology, from breathing to journaling.32 guides
- RelationshipsThe psychology of attachment, communication, conflict and connection.30 guides
- Life Stages & CommunitiesChildhood to retirement, parenting, school, work and the communities we belong to.57 guides
- ComparisonsSide-by-side explainers for terms that are easy to confuse.29 guides
- Study ResourcesAP Psychology, printable study guides, book summaries and interactive tools.5 guides
New to psychology? Start here
All basics- CompareWhat Is Psychology?What is psychology? The scientific study of mind and behavior: a plain-English definition, its history, major branches like cognitive and developmental, and methods.
- BasicsPsychology BasicsPsychology basics for beginners: the 5 key theories, core concepts, research methods, major branches and common myths, explained in one clear guide.
- ExperimentsResearch Methods in PsychologyResearch methods in psychology explained: experiments, correlational studies, observation, surveys, case studies, sampling, statistics, validity and ethics.
- BasicsPsychology TimelinePsychology timeline of key dates and people: from ancient philosophy and Wundt's 1879 lab through behaviorism and the cognitive revolution to modern neuroscience.
- PsychologistsFamous PsychologistsThe most famous psychologists of all time, from Freud, Skinner, and Piaget to Kahneman: a top-10 table, 40+ profiles, key theories, and how they're ranked.
- StudyAP Psychology Complete Study GuideAP Psychology study guide for the current course: the five units, key terms and researchers, the AAQ and EBQ free-response questions, and study plans that work.
The branches of psychology
Overview- Cognitive PsychologyCognitive psychology is the study of mental processes such as memory, attention, perception and reasoning. Its history, key theories, examples and applications.
- Developmental PsychologyDevelopmental psychology explained: the 8 lifespan stages, key theories from Piaget, Erikson and Bowlby, and how people change from birth to old age.
- Social PsychologySocial psychology studies how other people shape our thoughts and behavior: definition, theories, classic studies like Asch and Milgram, pros and cons.
- Clinical PsychologyClinical psychology explained: what clinical psychologists do, assessment, evidence-based therapies, specialties, and how it differs from forensic psychology.
- Humanistic PsychologyHumanistic psychology explained: the third-force approach of Maslow and Rogers, its beliefs about free will, the self and self-actualization, therapy and critiques.
- Positive PsychologyPositive psychology, the science of well-being: PERMA, character strengths, flow, what the evidence shows about interventions, and the field's main criticisms.
- Gestalt PsychologyWhat is gestalt psychology? The school founded by Wertheimer, Köhler and Koffka, its theory of perception, the 7 gestalt principles, insight learning and legacy.
- Evolutionary PsychologyEvolutionary psychology explains how natural selection shaped human behavior, emotions, and mating strategies. Clear guide to adaptive mechanisms and key theories.
- Forensic PsychologyForensic psychology is psychology applied to the legal system. Learn what forensic psychologists do, the field's history, education path, careers and salary.
- NeuropsychologyNeuropsychology explained: how brain structure and damage shape behavior, thinking, and emotion. Explore its history, key figures, assessment methods, and careers.
- Personality PsychologyPersonality psychology explained: how psychologists define, measure and explain personality, from Freud and Allport to the Big Five, stability and change.
- Health PsychologyHealth psychology explained: the biopsychosocial model, how stress affects the body, health behavior change theories, chronic illness, pain and careers.
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Landmark experiments
AllStudying for AP Psychology or an intro course?
Unit-by-unit AP Psychology review, 20 printable study guides, book summaries and an interactive cognitive bias test.
How we write
Every guide is written for clarity and checked against peer-reviewed research, standard textbooks and guidance from organisations such as the American Psychological Association, NIMH, the NHS and the World Health Organization. Pages show when they were last updated. iPsychology is an educational resource: we explain ideas and evidence, and we never offer diagnosis or medical advice. Read our editorial standards.