AP Psychology study guide

The history, approaches, research methods, and ethics that define psychology as a science.

What you need to know

Theories and approaches

Psychology is the scientific study of behavior and mental processes. The earliest schools were structuralism (Wundt, breaking consciousness into parts) and functionalism (James, how the mind helps adapt). Behaviorism (Watson, Skinner) focused only on observable behavior; psychoanalysis (Freud) on the unconscious; humanism (Rogers, Maslow) on growth and potential.

Modern perspectives include biological, cognitive, behavioral, sociocultural, humanistic, and evolutionary approaches. The biopsychosocial model combines biological, psychological, and social factors to explain behavior.

Research methods

Descriptive methods — naturalistic observation, case studies, and surveys — describe behavior but cannot establish cause and effect. Correlational studies measure relationships (r from −1 to +1) but correlation is not causation.

Experiments are the gold standard: researchers manipulate an independent variable and measure a dependent variable, using random assignment and control groups. Confounds, placebo effects, and experimenter bias must be controlled.

Ethics and measurement

Ethical research requires informed consent, confidentiality, debriefing, and the minimization of harm. Studies with deception must be justified.

Statistics summarize data: measures of central tendency (mean, median, mode), spread (range, standard deviation), and significance testing. Effect size and statistical significance help judge whether results matter.

Key terms

• Structuralism — The school that analyzed consciousness into its basic elements.
• Functionalism — The school that studied how the mind helps people adapt.
• Behaviorism — The approach focusing only on observable behavior.
• Psychoanalysis — Freud's approach emphasizing the unconscious mind.
• Humanism — The approach emphasizing personal growth and potential.
• Biopsychosocial model — Combining biological, psychological, and social factors.
• Correlation — A measure of the relationship between two variables (r from −1 to +1).
• Independent variable — The variable the experimenter manipulates.
• Dependent variable — The variable that is measured.
• Random assignment — Assigning participants to groups by chance.
• Informed consent — Participants' agreement after being told the study's nature.
• Confounding variable — An unintended variable that could affect the results.
• Debriefing — Explaining the study to participants afterward.

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The nervous system, neurons, the brain, and how biology drives thought and action.

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The nervous system and neurons

Neurons are the brain's signaling cells. A neuron fires an action potential when stimulation passes its threshold, an all-or-nothing electrical pulse that travels down the axon. Neurotransmitters cross the synapse and bind receptors on the next neuron.

The nervous system splits into the central nervous system (brain and spinal cord) and the peripheral nervous system (which includes the autonomic system — sympathetic for arousal, parasympathetic for calm — and the somatic system for voluntary movement).

The brain and its functions

The hindbrain (medulla, pons, cerebellum) handles vital functions and coordination. The midbrain routes sensory information. The forebrain contains the thalamus (relay), hypothalamus (homeostasis), amygdala (emotion), hippocampus (memory), and the cerebral cortex.

The cortex's four lobes have specialties: frontal (planning and personality), parietal (sensation and spatial sense), temporal (hearing and language), and occipital (vision). The two hemispheres specialize: left is usually language-dominant; the right handles spatial and holistic tasks. Split-brain research revealed this lateralization.

Genetics and the endocrine system

Genes, inherited through chromosomes, shape behavior, but environment (experience) interacts with genetics — this is the nature-nurture question. Twin and adoption studies help separate genetic and environmental influence.

The endocrine system uses hormones released by glands such as the pituitary, thyroid, adrenal, and gonads. Hormones travel in the blood and have slower, longer-lasting effects than neurotransmitters.

Key terms

• Neuron — The signaling cell of the nervous system.
• Action potential — The all-or-nothing electrical impulse that travels down the axon.
• Synapse — The junction between neurons where neurotransmitters cross.
• Neurotransmitter — A chemical messenger that carries signals across the synapse.
• Central nervous system — The brain and spinal cord.
• Sympathetic nervous system — The arousal system that readies the body for action.
• Parasympathetic nervous system — The system that calms the body and restores balance.
• Amygdala — A brain region central to emotion.
• Hippocampus — A brain region essential for forming new memories.
• Cerebral cortex — The outer layer of the brain responsible for higher functions.
• Endocrine system — The glandular system that releases hormones.
• Nature-nurture — The question of how genes and environment shape behavior.

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How the senses take in information and how the brain interprets it.

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Sensation basics

Sensation is the detection of physical stimuli by sensory receptors. Absolute threshold is the minimum stimulation needed for detection; difference threshold (just noticeable difference) is the smallest change that can be detected, governed by Weber's law.

Sensory adaptation is the decreasing responsiveness to constant stimulation. Signal detection theory explains that perception depends on both stimulus strength and the perceiver's state.

Vision and hearing

Light enters the eye through the cornea and pupil, is focused by the lens, and hits the retina. Rods detect light and dark; cones detect color. The optic nerve carries signals to the brain, which processes them in the visual cortex.

Sound waves are collected by the ear and turned into movement by the eardrum and ossicles. The cochlea converts vibrations into neural signals; the brain processes pitch, loudness, and location.

Perception principles

Perception organizes sensation into meaning. Gestalt principles describe how we group stimuli: proximity, similarity, continuity, closure, and figure-ground.

Perceptual constancies let us recognize objects despite changes (size, shape, color constancy). Depth perception relies on binocular cues (retinal disparity, convergence) and monocular cues (relative size, interposition, linear perspective).

Key terms

• Sensation — Detection of physical stimuli by sensory receptors.
• Perception — Interpretation of sensory information by the brain.
• Absolute threshold — The minimum stimulation needed to detect a stimulus.
• Difference threshold — The smallest detectable change in a stimulus.
• Weber's law — The just-noticeable difference is a constant proportion of the stimulus.
• Sensory adaptation — Decreased responsiveness to constant stimulation.
• Rods — Retinal cells that detect light and dark.
• Cones — Retinal cells that detect color.
• Cochlea — The inner-ear structure that converts sound to neural signals.
• Gestalt principles — Rules by which we group visual stimuli into wholes.
• Depth perception — Perceiving distance through binocular and monocular cues.

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How experience changes behavior: classical conditioning, operant conditioning, and observational learning.

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Classical conditioning

Pavlov's work showed that a neutral stimulus can come to trigger a response when paired with a stimulus that already does. In classical conditioning: an unconditioned stimulus (US) naturally produces an unconditioned response (UR); after pairing, a conditioned stimulus (CS) produces a conditioned response (CR).

Key phenomena: acquisition (learning the association), extinction (CS no longer paired → response fades), spontaneous recovery (response returns), generalization (similar stimuli trigger it), and discrimination (only the exact CS triggers it).

Operant conditioning

In operant conditioning (Skinner), behavior is shaped by consequences. Reinforcement increases behavior; punishment decreases it. Positive means adding something; negative means removing something. So positive reinforcement adds a reward, negative reinforcement removes an unpleasant stimulus, positive punishment adds an unpleasant consequence, and negative punishment removes something pleasant.

Schedules of reinforcement affect learning speed and persistence: fixed and variable, ratio (based on responses) and interval (based on time). Variable schedules produce the most resistance to extinction. Shaping reinforces successive approximations toward a goal.

Observational learning

Bandura showed that people learn by watching models. The Bobo doll experiment demonstrated that children imitate aggressive models. Observational learning requires attention, retention, reproduction, and motivation.

Latent learning (Tolman) shows learning can occur without immediate reinforcement, revealed only when needed — as in rats that learn mazes without rewards.

Key terms

• Classical conditioning — Learning where a neutral stimulus triggers a learned response through association.
• Unconditioned stimulus — A stimulus that naturally triggers a response.
• Conditioned stimulus — A learned trigger for a response.
• Extinction — The fading of a learned response when pairing stops.
• Spontaneous recovery — The return of a learned response after a pause.
• Generalization — Responding to stimuli similar to the conditioned stimulus.
• Operant conditioning — Learning shaped by consequences.
• Reinforcement — A consequence that increases behavior.
• Punishment — A consequence that decreases behavior.
• Shaping — Reinforcing successive approximations of a desired behavior.
• Observational learning — Learning by watching others.
• Latent learning — Learning that occurs but is only shown when useful.

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Memory, thinking, problem solving, and how the mind stores and uses information.

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Memory systems

Memory is processed in stages: sensory memory (very brief), short-term or working memory (about 7±2 items), and long-term memory (virtually unlimited). Encoding, storage, and retrieval are the three processes.

Forgetting happens through encoding failure, interference (retroactive and proactive), and retrieval failure. Retrieval is aided by cues, context, and state (context-dependent and state-dependent memory).

Thinking and problem solving

Concepts are mental groupings of similar things. We solve problems using algorithms (step-by-step) or heuristics (mental shortcuts, faster but biased). Functional fixedness and mental sets can block insight.

Cognitive biases affect judgment: confirmation bias (seeking confirming evidence), availability heuristic (overweighting vivid examples), and the anchoring effect. Framing changes decisions by altering how choices are presented.

Language and intelligence

Language develops through milestones: babbling, holophrases, two-word speech, and telegraphic speech. The theories of Chomsky (innate language acquisition device) and Skinner (learning through reinforcement) offer competing accounts.

Intelligence is measured by tests with reliability (consistency) and validity (what they claim to measure). Spearman proposed general intelligence (g); Gardner proposed multiple intelligences; Sternberg proposed analytical, creative, and practical intelligences. IQ scores follow a normal distribution with mean 100.

Key terms

• Sensory memory — Brief storage of sensory information.
• Working memory — The active, limited-capacity system holding current information.
• Long-term memory — The relatively permanent store of information.
• Encoding — Putting information into memory.
• Retrieval — Getting information out of memory.
• Retroactive interference — New learning disrupting old memories.
• Proactive interference — Old learning disrupting new memories.
• Heuristic — A fast, biased mental shortcut.
• Confirmation bias — Seeking information that confirms existing beliefs.
• Availability heuristic — Judging likelihood by how easily examples come to mind.
• Reliability — The consistency of a test's results.
• Validity — Whether a test measures what it claims to measure.
• g factor — Spearman's general intelligence factor.

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How people change across the lifespan: physical, cognitive, social, and moral development.

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Prenatal and infant development

Development begins at conception. Teratogens — substances like alcohol and drugs — can damage the developing fetus. Newborns arrive with reflexes, and attachment to caregivers is a key early milestone.

Harlow's monkey studies showed attachment is about comfort, not food. Ainsworth's Strange Situation identified secure, avoidant, and anxious attachment styles. Erikson's stages begin with trust versus mistrust in infancy.

Cognitive development

Piaget described stages of cognitive growth: sensorimotor (object permanence develops), preoperational (egocentrism, no conservation), concrete operational (logic about concrete objects, conservation), and formal operational (abstract thinking).

Vygotsky emphasized social learning and the zone of proximal development (with scaffolding). Critics note Piaget underestimated children's abilities and that development is more continuous than stage-like.

Adolescence and beyond

Adolescence brings identity formation (Erikson's identity vs. role confusion), moral reasoning (Kohlberg's preconventional, conventional, postconventional levels), and adolescent egocentrism.

Adulthood involves intimacy (Erikson), generativity, and integrity. Social relationships, career, and family shape well-being. Research on aging shows cognitive abilities like processing speed may decline, while wisdom and experience can grow.

Key terms

• Teratogen — A substance that harms prenatal development.
• Attachment — The emotional bond between infant and caregiver.
• Strange Situation — Ainsworth's procedure measuring attachment styles.
• Object permanence — Knowing an object exists when out of sight.
• Egocentrism — Inability to see the world from another's perspective.
• Conservation — Knowing quantity stays the same despite changes in appearance.
• Zone of proximal development — The range of tasks a learner can do with help.
• Scaffolding — Adjusting support as a learner gains skill.
• Identity vs. role confusion — Erikson's adolescent stage of forming a sense of self.
• Kohlberg's stages — Preconventional, conventional, and postconventional moral reasoning.
• Crystallized intelligence — Accumulated knowledge and experience.

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What drives behavior, how emotions work, and the major theories of personality.

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Motivation and emotion

Motivation theories include drive-reduction (needs create drives), instinct, arousal (seeking optimal stimulation), and incentive (external rewards). Maslow's hierarchy orders needs from physiological to self-actualization.

Theories of emotion: James-Lange (stimulus → physiological response → emotion), Cannon-Bard (simultaneous), Schachter-Singer two-factor (physiological arousal + cognitive label), and the facial feedback hypothesis. The Yerkes-Dodson law says optimal performance occurs at moderate arousal.

Theories of personality

Freud's psychoanalytic theory emphasized the id (pleasure), ego (reality), and superego (morality), with defense mechanisms and the unconscious. He described psychosexual stages.

Humanistic theories (Rogers, Maslow) emphasized self-concept and self-actualization. Trait theories (Allport, Eysenck, Big Five) describe personality through stable traits. The Big Five are openness, conscientiousness, extraversion, agreeableness, and neuroticism (OCEAN).

Measuring personality

Personality is measured through self-report inventories (true/false questions), projective tests (Rorschach, TAT), and behavioral observation. The social-cognitive perspective (Bandura) emphasizes the interaction of traits, environment, and behavior, with the concept of reciprocal determinism.

Key terms

• Drive-reduction theory — The idea that needs create drives that motivate behavior.
• Maslow's hierarchy — A pyramid of needs from physiological to self-actualization.
• Yerkes-Dodson law — Moderate arousal produces optimal performance.
• James-Lange theory — Emotion follows physiological arousal.
• Two-factor theory — Emotion is physiological arousal plus a cognitive label.
• Id — The pleasure-seeking part of the personality.
• Superego — The moral part of the personality.
• Defense mechanism — An unconscious strategy reducing anxiety.
• Big Five (OCEAN) — Openness, conscientiousness, extraversion, agreeableness, neuroticism.
• Self-actualization — Realizing one's full potential.
• Reciprocal determinism — Behavior, environment, and traits influence each other.
• Projective test — A test presenting ambiguous stimuli to reveal personality.

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Psychological disorders, their symptoms, and the treatments used to help people.

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Classifying disorders

Psychological disorders are diagnosed using the DSM-5, the manual of diagnostic criteria. Disorders are defined by distressing, dysfunctional patterns that cause harm.

Perspectives on causation include biological (genetics, brain chemistry), psychological (thoughts, learning), and sociocultural (environment and culture). The biopsychosocial model integrates them, and the diathesis-stress model says disorders arise when vulnerability meets stress.

Major disorder categories

Anxiety disorders include generalized anxiety, panic disorder, phobias, and obsessive-compulsive disorder. They feature excessive fear and worry, often maintained by avoidance.

Mood disorders include major depressive disorder (persistent low mood) and bipolar disorder (mood swings between mania and depression). Schizophrenia involves psychosis: hallucinations, delusions, disorganized speech, and negative symptoms.

Dissociative disorders (amnesia, identity disturbance), somatic symptom disorders, and personality disorders (paranoid, borderline, antisocial) round out the diagnostic picture.

Treatments

Psychotherapy comes in many forms: psychodynamic, humanistic (person-centered), cognitive (changing thoughts), cognitive-behavioral (thoughts + behaviors), and behavior therapies (systematic desensitization, exposure, token economies).

Biomedical treatments include psychotropic medications (antidepressants, antipsychotics, antianxiety, mood stabilizers), electroconvulsive therapy (ECT) for severe depression, and newer approaches. Effective treatment often combines therapy and medication.

Key terms

• DSM-5 — The manual used to diagnose psychological disorders.
• Biopsychosocial model — Explaining disorders through biological, psychological, and social factors.
• Diathesis-stress model — Disorders arise when a vulnerability meets stress.
• Generalized anxiety disorder — Persistent, excessive worry about many things.
• Panic disorder — Recurrent, unexpected panic attacks.
• Major depressive disorder — Persistent depressed mood and loss of interest.
• Bipolar disorder — Mood swings between mania and depression.
• Schizophrenia — A disorder with psychosis: hallucinations, delusions, disorganization.
• Hallucination — A false sensory perception, like hearing voices.
• Delusion — A fixed false belief.
• Cognitive-behavioral therapy — Treatment changing maladaptive thoughts and behaviors.
• Systematic desensitization — Gradual exposure with relaxation to reduce phobia.

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How we think about, influence, and relate to each other in social contexts.

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Social thinking

Attribution theory explains how we judge causes of behavior. The fundamental attribution error is over-attributing others' behavior to disposition while underestimating situation. The self-serving bias credits ourselves for success but blames situations for failure.

Attitudes — evaluations that can change behavior — are studied through persuasion (central and peripheral routes) and cognitive dissonance (discomfort from inconsistent attitudes and behavior, motivating change).

Social influence

Conformity is adjusting behavior to match a group (Asch's line studies). Obedience is following authority (Milgram's shock studies). Group influence includes deindividuation (loss of self-awareness in groups), group polarization, groupthink, and social loafing.

Compliance techniques include the foot-in-the-door (small request then larger), door-in-the-face, and reciprocity.

Social relations

Prejudice is an unjustified negative attitude; discrimination is the behavior. Stereotypes are cognitive shortcuts. The just-world phenomenon and in-group/out-group bias help explain prejudice.

Prosocial behavior includes altruism and helping. The bystander effect shows people help less when others are present (diffusion of responsibility). Aggression has biological and social influences. Attraction is shaped by proximity, similarity, and reciprocity.

Key terms

• Fundamental attribution error — Over-attributing others' behavior to disposition.
• Self-serving bias — Taking credit for success, blaming situation for failure.
• Cognitive dissonance — Discomfort from inconsistent attitudes and behavior.
• Conformity — Adjusting behavior to match a group.
• Obedience — Following orders from authority.
• Groupthink — Group consensus overriding critical thinking.
• Deindividuation — Loss of self-awareness in a group.
• Foot-in-the-door — Getting compliance by starting with a small request.
• Prejudice — An unjustified negative attitude toward a group.
• Discrimination — Unjustified negative behavior toward a group.
• Bystander effect — People help less when others are present.
• Diffusion of responsibility — Assuming someone else will act.

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