MCAT Psychological, Social, and Biological Foundations of Behavior (P/S) — Study Guide (Wave 1)

Status: draft_awaiting_sme. Grounded in consensus introductory psychology (OpenStax Psychology) and sociology (OpenStax Introduction to Sociology). All content original.

How to use this: P/S rewards precise vocabulary and the ability to discriminate between neighboring terms. Each section flags the terms most often confused on test day. Treat the "Easily confused with…" call-outs as your highest-yield review.

Foundational Concept 6 — Biological, psychological, and sociocultural factors influence how individuals perceive, think about, and react to the world

6A — Sensing the environment

High-yield idea. Sensation is the detection of physical stimuli by sensory receptors; perception is the brain's organization and interpretation of that input. Sensation is bottom-up (data driven from receptors), perception layers in top-down processing (expectations, context).

Transduction converts physical energy (light, sound pressure, chemical molecules) into electrochemical neural signals. Each modality has specialized receptors and a labeled pathway to a primary cortical area.

Thresholds and psychophysics.

Absolute threshold — minimum stimulus intensity detectable 50% of the time.
Difference threshold (just-noticeable difference, JND) — smallest detectable change between two stimuli.
Weber's law — the JND is a constant proportion of the original stimulus, not a constant amount.
Signal detection theory (SDT) — separates true sensory sensitivity (d′) from response bias (criterion). Outcomes: hits, misses, false alarms, correct rejections. SDT explains why motivation, expectation, and payoffs shift detection even when the stimulus is unchanged.
Sensory adaptation — decreased responsiveness to a constant, unchanging stimulus over time.

Vision. Light → cornea → pupil → lens → retina. Retinal photoreceptors: rods (dim light, peripheral, achromatic, high sensitivity) and cones (bright light, fovea, color, high acuity). Signals pass retina → optic nerve → (optic chiasm) → thalamus (LGN) → primary visual cortex (occipital lobe). Color vision: trichromatic (Young–Helmholtz) theory at the receptor level (three cone types) plus opponent-process theory downstream (red–green, blue–yellow, black–white channels — explains afterimages).

Hearing. Sound waves → outer ear → tympanic membrane → ossicles → cochlea (basilar membrane, hair cells) → auditory nerve → temporal lobe. Pitch coding: place theory (high frequencies localize on the basilar membrane) vs frequency/temporal theory (firing rate tracks low frequencies); the volley principle extends frequency theory.

Other senses. Olfaction (chemoreception, projects partly without thalamic relay), gustation (five basic tastes), somatosensation, kinesthesia (limb position via muscle/joint receptors), and the vestibular sense (balance, via semicircular canals and otolith organs).

Easily confused with…

Sensation vs perception: detection of stimuli vs interpretation of stimuli.
Absolute threshold vs difference threshold: detecting a stimulus at all vs detecting a change.
Rods vs cones: dim-light/peripheral/no-color vs bright-light/foveal/color.
Trichromatic vs opponent-process: receptor-level (three cones) vs neural-channel level (afterimages).

6B — Making sense of the environment

Attention. Selective attention (focusing on one stream — the cocktail party effect) vs divided attention (multitasking, limited capacity). Inattentional blindness and change blindness show failures to perceive unattended stimuli.

Perceptual organization — Gestalt principles. Proximity, similarity, continuity (good continuation), closure, figure–ground, and the law of Prägnanz (we perceive the simplest, most stable form). Perceptual constancy (size, shape, color) keeps objects stable despite changing retinal images.

Cognition and problem-solving.

Algorithm — step-by-step procedure guaranteeing a solution.
Heuristic — mental shortcut; faster but error-prone.
- Availability heuristic — judging likelihood by how easily examples come to mind.
- Representativeness heuristic — judging by resemblance to a prototype (ignores base rates → base-rate fallacy).
Confirmation bias — seeking information that confirms existing beliefs.
Mental set and functional fixedness — fixation on familiar approaches/uses; obstacles to insight.
Framing effects — decisions shift with how options are described.

Memory.

Atkinson–Shiffrin (modal) model: sensory memory → short-term/working memory → long-term memory.
Sensory memory: iconic (visual, ~0.5 s), echoic (auditory, ~3–4 s).
Working memory (Baddeley): central executive + phonological loop + visuospatial sketchpad + episodic buffer.
Long-term memory: explicit/declarative (episodic = events; semantic = facts) vs implicit/nondeclarative (procedural skills, priming, conditioning).
Encoding: shallow vs deep; levels of processing (semantic encoding is most durable). Spacing effect, method of loci, chunking.
Retrieval: recall vs recognition; encoding specificity; context- and state-dependent memory; serial position effect (primacy from LTM rehearsal, recency from STM).
Forgetting: proactive interference (old disrupts new) vs retroactive interference (new disrupts old); decay; retrieval failure (tip-of-the-tongue). Ebbinghaus forgetting curve.
Memory distortion: misinformation effect, source-monitoring errors, false memories (Loftus).
Neuro: hippocampus (consolidation of explicit memory), amygdala (emotional memory), cerebellum (procedural), long-term potentiation (LTP) as the synaptic basis.

Intelligence. General intelligence g (Spearman) vs multiple/triarchic theories (Gardner, Sternberg). Fluid (reasoning with novel problems) vs crystallized (accumulated knowledge) intelligence.

Language. Phonemes → morphemes → semantics → syntax → pragmatics. Milestones: babbling → one-word → telegraphic speech. Nativist (Chomsky, LAD) vs learning vs interactionist theories. Whorf's linguistic relativity hypothesis (language shapes thought).

Consciousness and sleep. Circadian rhythm (suprachiasmatic nucleus, melatonin). Sleep stages by EEG: N1 (theta), N2 (sleep spindles, K-complexes), N3 (delta, slow-wave), and REM (paradoxical sleep, dreaming, atonia). Theories of dreaming: activation–synthesis vs information-processing/consolidation.

Easily confused with…

Availability vs representativeness heuristic: ease of recall vs resemblance to a prototype.
Proactive vs retroactive interference: pro = prior learning interferes forward; retro = new learning interferes backward.
Explicit/declarative vs implicit/procedural memory: conscious facts/events vs unconscious skills.
Iconic vs echoic memory: visual vs auditory sensory store.
Fluid vs crystallized intelligence: on-the-spot reasoning vs stored knowledge.

6C — Responding to the world

Emotion. Components: physiological arousal, behavioral expression, subjective/cognitive experience. Theories:

James–Lange — stimulus → bodily arousal → emotion ("I feel afraid because my heart pounds").
Cannon–Bard — arousal and emotion occur simultaneously.
Schachter–Singer two-factor — arousal + cognitive label/attribution = emotion.
Lazarus appraisal — cognitive appraisal precedes emotion.
Yerkes–Dodson law — performance peaks at moderate arousal (inverted-U). Neuro: amygdala (fear), limbic system; the autonomic nervous system drives arousal.

Stress. Primary appraisal (Is this a threat?) and secondary appraisal (Can I cope?) — Lazarus. General adaptation syndrome (Selye): alarm → resistance → exhaustion. The HPA axis releases cortisol. Coping: problem-focused (change the stressor) vs emotion-focused (manage the response).

Easily confused with…

James–Lange vs Cannon–Bard vs Schachter–Singer: arousal-first vs simultaneous vs arousal-plus-cognition.
Problem-focused vs emotion-focused coping: fix the stressor vs regulate the feeling.
Primary vs secondary appraisal: is it threatening? vs can I handle it?

Active recall — FC 6

State Weber's law and explain why signal detection theory separates d′ from criterion.
Contrast proactive and retroactive interference with one example each.
A person reinterprets racing heartbeat as excitement before a date. Which emotion theory does this illustrate, and how does it differ from James–Lange?

Foundational Concept 7 — Biological, psychological, and sociocultural factors influence behavior and behavior change

7A — Individual influences on behavior

Biological bases. Neuron: dendrites → soma → axon → terminals; action potential, synaptic transmission. Central (brain, spinal cord) vs peripheral nervous system; peripheral splits into somatic (voluntary) and autonomic (sympathetic = fight-or-flight; parasympathetic = rest-and-digest). Key neurotransmitters: dopamine, serotonin, GABA (inhibitory), glutamate (excitatory), acetylcholine. Endocrine signaling via hormones (slower, longer-lasting than neural). Genetics: genotype vs phenotype, heritability, gene–environment interaction.

Personality theories.

Psychoanalytic (Freud): id/ego/superego; defense mechanisms.
Humanistic (Maslow, Rogers): self-actualization, unconditional positive regard.
Trait (Big Five / OCEAN): Openness, Conscientiousness, Extraversion, Agreeableness, Neuroticism.
Social-cognitive (Bandura): reciprocal determinism (person, behavior, environment interact); locus of control; self-efficacy.
Biological/temperament approaches (Eysenck).

Psychological disorders. DSM categories: anxiety, depressive, bipolar, obsessive-compulsive, trauma- and stressor-related (PTSD), schizophrenia spectrum (positive vs negative symptoms), dissociative, personality disorders. Models: biomedical vs biopsychosocial.

Motivation. Drive-reduction theory (homeostasis), arousal theory (optimal arousal), incentive theory, Maslow's hierarchy of needs. Intrinsic vs extrinsic motivation; the overjustification effect (extrinsic reward undermines intrinsic interest). Self-determination theory (autonomy, competence, relatedness).

Attitudes. Tri-component (affective, behavioral, cognitive). Cognitive dissonance (Festinger): discomfort from inconsistent attitudes/behaviors drives attitude change.

Easily confused with…

Sympathetic vs parasympathetic: arousal/fight-or-flight vs calming/rest-and-digest.
Intrinsic vs extrinsic motivation: internal satisfaction vs external reward.
Positive vs negative symptoms (schizophrenia): added experiences (hallucinations) vs absent normal function (flat affect, avolition) — not "good/bad."

7B — Social processes that influence human behavior

Socialization — lifelong learning of norms, values, and roles; primary (childhood/family) vs secondary (later institutions). Agents: family, peers, school, media.
Conformity — adjusting behavior/beliefs to a group (Asch line studies; normative vs informational social influence).
Obedience — compliance with authority (Milgram).
Group dynamics: groupthink (consensus pressure overrides realistic appraisal), group polarization (group shifts toward more extreme position), social facilitation (improved performance on easy tasks when observed), social loafing (reduced individual effort in groups).
Deindividuation — loss of self-awareness/restraint in groups.
Bystander effect — less likely to help as the number of bystanders rises; diffusion of responsibility.
Culture and behavior: individualist vs collectivist cultures.

Easily confused with…

Conformity vs obedience vs compliance: peer/group norms vs authority command vs direct request.
Normative vs informational social influence: fit in / be liked vs be correct / accept others' info.
Social facilitation vs social loafing: presence of others helps (individual, evaluated) vs effort drops (pooled, anonymous).
Groupthink vs group polarization: suppressing dissent for harmony vs amplifying the group's leaning.

7C — Attitude and behavior change

Learning.

Classical conditioning (Pavlov): US → UR; pairing NS with US makes CS → CR. Processes: acquisition, extinction, spontaneous recovery, generalization, discrimination. Higher-order conditioning.
Operant conditioning (Skinner): behavior shaped by consequences.
- Positive reinforcement (add desirable) and negative reinforcement (remove aversive) both increase behavior.
- Positive punishment (add aversive) and negative punishment (remove desirable) both decrease behavior.
- Reinforcement schedules: fixed/variable × ratio/interval. Variable-ratio yields the highest, most extinction-resistant response rate.
- Shaping (reinforcing successive approximations).
Observational learning (Bandura, Bobo doll): modeling, vicarious reinforcement.
Latent learning and insight learning (cognitive components).

Attitude/behavior-change theories. Elaboration likelihood model (ELM): central route (deep processing of argument quality, durable change) vs peripheral route (surface cues like attractiveness/source, less durable). Cognitive dissonance as a change mechanism.

Easily confused with…

Negative reinforcement vs punishment: negative reinforcement increases behavior by removing something aversive; punishment decreases behavior. (The single most-tested confusion in 7C.)
Classical vs operant conditioning: involuntary association of stimuli vs voluntary behavior shaped by consequences.
Central vs peripheral route (ELM): argument substance vs surface cues.

Active recall — FC 7

Distinguish negative reinforcement from positive punishment with an example of each, and state the effect of each on behavior.
Why does the bystander effect predict less helping with more witnesses? Name the mechanism.
Under ELM, when is persuasion likely to take the central route, and why is the resulting change more durable?

Foundational Concept 8 — How we think about ourselves and others and interact with others

8A — Self-identity

Self-concept — the totality of beliefs about oneself; self-schemas.
Self-esteem — evaluative/affective component of self-concept.
Self-efficacy (Bandura) — belief in one's capability for a specific task. (Distinct from self-esteem.)
Identity formation: Erikson's psychosocial stages (esp. identity vs role confusion); Marcia's identity statuses.
Social identity theory (Tajfel & Turner): identity derives partly from group membership; drives in-group favoritism.
Looking-glass self (Cooley) — self-concept formed by imagining how others see us.
Reference group — group used as a standard for self-evaluation.

Easily confused with…

Self-esteem vs self-efficacy: global self-worth vs task-specific competence belief.
Looking-glass self vs role-taking (Mead): seeing self through others' eyes vs taking others' perspectives in interaction.

8B — Social thinking

Attribution theory. Explaining behavior via internal/dispositional vs external/situational causes (Kelley's covariation: consistency, distinctiveness, consensus).

Fundamental attribution error (FAE): overweighting dispositional causes for others' behavior, underweighting the situation.
Actor–observer bias: attributing our own behavior to the situation but others' to disposition.
Self-serving bias: crediting success to self (internal), blaming failure on circumstances (external).
Just-world hypothesis — belief that people get what they deserve.

Prejudice, stereotypes, discrimination.

Stereotype — cognitive (belief about a group).
Prejudice — affective (attitude/feeling toward a group).
Discrimination — behavioral (differential treatment).
Ethnocentrism — judging other cultures by one's own standards.
Stereotype threat — anxiety about confirming a negative stereotype impairs performance.

Easily confused with…

FAE vs actor–observer bias: FAE is about others' behavior; actor–observer contrasts self (situational) vs others (dispositional).
Stereotype vs prejudice vs discrimination: thought vs feeling vs action.
Ethnocentrism vs cultural relativism: judging by own standards vs understanding a culture on its own terms.

8C — Social interactions

Self-presentation / impression management; front-stage vs back-stage (Goffman's dramaturgy).
Expression of emotion: universal basic emotions; display rules (cultural norms governing expression).
Interpersonal attraction: proximity (mere-exposure effect), similarity, physical attractiveness, reciprocal liking.
Aggression: frustration–aggression hypothesis; biological and social-learning contributions.
Altruism / prosocial behavior: kin selection, reciprocal altruism, the empathy–altruism hypothesis vs egoistic (negative-state relief) accounts.
Social support: instrumental vs emotional; buffers stress.

Easily confused with…

Altruism vs egoistic helping: helping for the other's welfare vs to relieve one's own distress.
Mere-exposure effect vs similarity: liking from repeated contact vs liking from shared traits.

Active recall — FC 8

Differentiate the fundamental attribution error from the actor–observer bias.
Sort stereotype, prejudice, and discrimination into cognitive, affective, and behavioral components.
Define self-efficacy and explain how it differs from self-esteem.

Foundational Concept 9 — Cultural and social differences influence well-being

9A — Understanding social structure

Theoretical approaches (macro vs micro).

Functionalism (Durkheim) — society as interrelated parts maintaining stability; manifest (intended) vs latent (unintended) functions; dysfunctions.
Conflict theory (Marx) — society as competition over scarce resources; power and inequality.
Symbolic interactionism (Mead, Blumer) — micro-level; meaning constructed through everyday symbolic interaction.
(Feminist theory and rational-choice/exchange theory also appear.)

Social institutions — education, family, religion, government, economy, medicine/health care. Concepts: roles, role conflict/strain, status (ascribed vs achieved), norms (folkways, mores, taboos), sanctions.

Culture. Material vs nonmaterial culture; values, beliefs, rituals; cultural lag; cultural diffusion. Social constructionism — categories (e.g., race, gender) are produced through social processes, not purely natural. Assimilation, multiculturalism, subcultures, countercultures.

Easily confused with…

Functionalism vs conflict vs symbolic interactionism: stability/integration (macro) vs power/inequality (macro) vs meaning-making (micro).
Manifest vs latent functions: intended/recognized vs unintended/unrecognized consequences.
Ascribed vs achieved status: assigned at birth/involuntary vs earned.
Folkways vs mores: everyday customs vs morally significant norms.

9B — Demographic characteristics and processes

Demographic structure: age, gender, sex, race/ethnicity, sexual orientation, immigration status.
Demographic transition — shift from high birth/death rates to low; fertility, mortality, migration.
Population pyramids; aging populations.
Social movements — relative deprivation, resource mobilization, new social movements.
Globalization, urbanization (and suburbanization, urban decline/renewal).

Easily confused with…

Sex vs gender: biological vs socially constructed roles/identity.
Immigration vs emigration: moving in vs moving out (net migration).

Active recall — FC 9

Compare functionalism, conflict theory, and symbolic interactionism on level of analysis and core focus.
Define manifest and latent functions with one example each.
Distinguish ascribed from achieved status.

Foundational Concept 10 — Social stratification and access to resources influence well-being

10A — Social inequality

Social stratification — hierarchical ranking of groups; caste (closed) vs class (open) systems.
Socioeconomic status (SES) — composite of income, wealth, education, occupation. (Income = flow; wealth = accumulated assets/net worth.)
Social mobility — intergenerational vs intragenerational; vertical vs horizontal. Meritocracy.
Poverty — absolute vs relative; social reproduction (inequality passed across generations).
Spatial inequality — residential segregation, redlining, environmental injustice, urban/suburban/rural disparities.
Health disparities — differences in health outcomes/access by SES, race, geography. Social determinants of health; healthcare access; the social gradient in health.
Power, privilege, prestige (Weber's three dimensions of stratification: class, status, party).
Global inequality and the culture of poverty debate.

Easily confused with…

Income vs wealth: periodic earnings vs total accumulated assets.
Intergenerational vs intragenerational mobility: across generations vs within one person's lifetime.
Absolute vs relative poverty: below a fixed subsistence line vs below the standard of one's society.
Caste vs class system: closed/birth-fixed vs open/mobility-possible.

Active recall — FC 10

Distinguish income from wealth and explain why wealth gaps often exceed income gaps.
Define residential segregation and connect it to a health disparity.
Contrast intergenerational and intragenerational mobility.

Cross-cutting: research methods and data reasoning (SIRS 3 & 4)

P/S passages frequently describe a study. Be ready to:

Identify independent vs dependent variables, operational definitions, and confounds.
Distinguish experimental (random assignment → causal claims) from correlational/observational designs (no causal claim; third-variable and directionality problems).
Read descriptive statistics (mean, median, mode, range, standard deviation, skew) and recognize when the median is more representative (skewed data).
Interpret correlation coefficients (sign and magnitude) without inferring causation.
Understand reliability (consistency: test–retest, inter-rater) vs validity (accuracy: internal, external/generalizability, construct).
Recognize sampling issues (random vs convenience samples), selection bias, response bias, demand characteristics, and the value of double-blind procedures and control groups.
Interpret statistical significance / p-values as the probability of the result under the null, and distinguish significance from effect size; note confidence intervals.

Easily confused with…

Reliability vs validity: consistent vs accurate (a reliably wrong measure is reliable but not valid).
Internal vs external validity: confound-free causal inference vs generalizability.
Correlation vs causation: association vs cause; watch for third variables and reverse causation.