Sensation. Raw detection. A rod fires when photons hit it.
Perception. Interpretation. “That’s my grandmother’s face.”
Key distinction: sensation = receptor-level. Perception = brain-level. If the passage says “detected” or “registered,” think sensation. If it says “recognized” or “identified,” think perception.
Absolute Threshold vs. Just Noticeable Difference (JND)
Absolute threshold. Minimum intensity to detect a stimulus 50% of the time. “Can I hear the phone at all?”
JND (difference threshold). Minimum CHANGE in a stimulus that’s detectable 50% of the time. “Is the phone getting louder?”
Key distinction: absolute threshold compares to nothing (silence). JND compares to an already-present stimulus.
Sensory Adaptation vs. Habituation
Sensory adaptation. Receptor-level. The receptor literally stops firing. Your nose stops smelling your perfume after an hour.
Habituation. Brain-level. The receptor still fires, but the brain filters the signal. You stop consciously hearing the AC unit hum.
Key distinction: adaptation = receptor fatigue. Habituation = CNS-level dismissal. Both reduce response, but for different biological reasons.
Transduction vs. Transmission
Transduction. Converting physical energy into a neural signal. Light → electrical impulse in a rod.
Transmission. Passing that neural signal along to other neurons.
Key distinction: transduction happens at the receptor (one step). Transmission happens between neurons (the relay).
Top-Down vs. Bottom-Up Processing
Bottom-up. Data-driven. Start with raw sensory input, build up to recognition. A baby seeing a new object.
Top-down. Expectation-driven. Start with what you expect to see, use it to interpret ambiguous input. “Where’s Waldo?”
Key distinction: bottom-up = no prior knowledge required. Top-down = uses prior knowledge to fill gaps (and can create illusions).
Trichromatic Theory vs. Opponent-Process Theory
Trichromatic (Young-Helmholtz). Three cone types (red, green, blue). Any color = a mix. Explains TV screens.
Opponent-process (Hering). Three opposing pairs (red-green, blue-yellow, black-white). Explains afterimages (stare at green → see red afterimage).
Key distinction: trichromatic operates at cones (retina). Opponent-process operates downstream (ganglion cells onward). Both are right at different stages.
Place Theory vs. Frequency Theory (Hearing)
Place theory. Different frequencies stimulate different LOCATIONS on the basilar membrane. Best for high frequencies (>2000 Hz).
Frequency theory. Neurons fire at the same rate as the incoming sound wave. Best for low frequencies.
Key distinction: place = which spot on the cochlea. Frequency = how fast the neurons fire. Both work together in the middle range.
Conductive vs. Sensorineural Hearing Loss
Conductive. Problem in the PATH of sound (wax, torn eardrum, fused ossicles). Patient hears their own voice normally (bone conduction) but struggles with external sound.
Sensorineural. Damage to HAIR CELLS or the auditory nerve. All sounds affected. Cochlear implants bypass dead hair cells.
Key distinction: conductive = mechanical blockage. Sensorineural = neural damage. If the passage says “loud concerts” or “aging,” think sensorineural.
Proprioception vs. Kinesthesia
Proprioception. Knowing where your body PARTS are in space right now. Touching your nose with eyes closed.
Kinesthesia. Knowing how your body is MOVING. Adjusting mid-step after tripping.
Key distinction: proprioception = static position (cognitive). Kinesthesia = active motion (behavioral). Close, but proprioception is about “where” and kinesthesia is about “how I’m moving.”
Pharmacology of Pain: Nociception vs. Thermoreception
Nociception. Pain detection. C fibers (slow, dull) and A-delta fibers (fast, sharp).
Thermoreception. Temperature detection. TrpV1 receptors (also detect capsaicin = why chili feels hot).
Key distinction: pain vs. temperature. TrpV1 blurs them - fires on heat OR capsaicin OR noxious pain. That’s why spicy food feels hot.
Labeled Line vs. Shape (Steric) Theory of Olfaction
Labeled line. Each odor receptor is “labeled” for a specific smell. One line = one odor.
Shape (steric) theory. Odor molecules fit receptors by MOLECULAR SHAPE, like a lock and key.
Key distinction: labeled-line = specific receptor-per-smell. Shape = lock-and-key fit. Shape theory is the modern dominant view.
Signal Detection: Sensitivity (d’) vs. Response Bias (c)
d’ (sensitivity). How well you can tell signal from noise. A property of the stimulus/detector.
c (response bias). Your strategy. Conservative = “I only say yes when sure.” Liberal = “I say yes often.”
Key distinction: d’ is about HOW WELL the person discriminates. c is about the strategy they choose. Two subjects can have the same d’ but opposite c.
NREM. No rapid eye movement. Includes N1, N2, N3 (deep sleep). Declarative memory consolidation. Dreams are duller and less memorable.
Key distinction: REM = paradoxical (active brain, paralyzed body). NREM = slower brain waves. Sleepwalking happens in N3 (NREM), NOT REM (muscles are paralyzed in REM).
Nightmares vs. Night Terrors
Nightmares. Scary dreams in REM sleep. Remembered. More common in older children/adults.
Night terrors. Sudden screaming/panic in N3 (deep NREM). NOT remembered. Common in young children.
Key distinction: nightmare = remembered REM dream. Night terror = unremembered N3 episode. Waking parents often see night terrors; the child won’t recall it.
Insomnia vs. Narcolepsy vs. Sleep Apnea
Insomnia. Trouble falling or staying asleep. Chronic, tiring. Treated with CBT-I first.
Narcolepsy. Sudden sleep attacks during the day, often with cataplexy (muscle collapse from strong emotion). Linked to low orexin.
Sleep apnea. Repeated breathing stops during sleep. Loud snoring, gasping awakenings, daytime fatigue despite full night in bed. Treated with CPAP.
Key distinction: insomnia = can’t sleep. Narcolepsy = falls asleep suddenly. Apnea = stops breathing during sleep. All three cause daytime fatigue but for very different reasons.
Tolerance vs. Dependence vs. Addiction vs. Withdrawal
Tolerance. Same dose produces less effect over time. Body has adapted.
Dependence (physical). Stopping produces withdrawal symptoms. Body NEEDS the drug to feel normal.
Addiction (substance use disorder). Compulsive use despite harm. A behavioral pattern, not just biology.
Withdrawal. Physical/mental symptoms when stopping. Opposite of the drug’s effects.
Key distinction: tolerance = needing more. Dependence = sickness when stopping. Addiction = can’t stop despite harm. A patient on long-term opioids for pain can be tolerant and dependent WITHOUT being addicted.
Opiate vs. Opioid
Opiate. Natural drugs derived from opium poppy (morphine, codeine).
Opioid. Broader term including opiates PLUS synthetic drugs (oxycodone, fentanyl, heroin, methadone).
Key distinction: all opiates are opioids; not all opioids are opiates. In everyday language the terms are used interchangeably; on the MCAT, opioid is the inclusive term.
Depressants vs. Stimulants vs. Hallucinogens vs. Opioids
Key distinction: target neurotransmitter. GABA = depressant. Dopamine/NE = stimulant. Serotonin = hallucinogen. Endorphin = opioid. Opioids are NOT depressants even though they sedate - they use different chemistry.
Dissociation vs. Social Influence (Theories of Hypnosis)
Dissociation theory. Hypnosis splits consciousness. Part obeys the hypnotist; a “hidden observer” stays aware (Hilgard).
Social influence theory. Hypnotized subjects play a role shaped by expectations, like actors caught up in their part. They sincerely experience what they’re told.
Key distinction: dissociation = split consciousness. Social influence = role-playing. Both predict similar behavior but explain it very differently.
Amphetamines. Block reuptake AND trigger dopamine RELEASE from the presynaptic cell. Longer lasting (e.g., Adderall, methamphetamine).
Key distinction: cocaine = blocks recycling. Amphetamines = block recycling AND dump out more dopamine. That’s why meth is more addictive than cocaine.
Freud’s Theory vs. Activation-Synthesis Hypothesis of Dreams
Activation-synthesis. Brainstem fires random neural signals; cortex stitches them into a narrative. Dreams may have NO deep meaning.
Key distinction: if the passage frames dreams as MEANINGFUL and symbolic, it’s Freudian. If it frames them as noise + interpretation, it’s activation-synthesis.
Sleep Deprivation Effects
REM deprivation. Emotional dysregulation, impaired procedural memory, REM rebound on next sleep.
Classical (Pavlov). Learning that one stimulus PREDICTS another. Dog salivates to bell because bell = food. Reflexive, involuntary. No consequences - just pairings.
Operant (Skinner). Learning that your BEHAVIOR produces consequences. Dog sits because sitting = treat. Voluntary. Behavior changes based on what follows it.
Positive vs. Negative (in Reinforcement/Punishment)
Positive. ADDING something to the environment.
Negative. REMOVING something from the environment.
Key distinction: these words don’t mean “good” or “bad.” They mean add vs. remove. A seatbelt buzzer REMOVED when you buckle = negative reinforcement.
Reinforcement vs. Punishment
Reinforcement. INCREASES a behavior.
Punishment. DECREASES a behavior.
Key distinction: outcome on behavior frequency, not on feelings. Cross with positive/negative for the full 2×2:
Add something
Remove something
Increase behavior
Positive reinforcement
Negative reinforcement
Decrease behavior
Positive punishment
Negative punishment
Examples:
Candy for good grades = positive reinforcement.
Buzzer stops when seatbelt buckled = negative reinforcement.
Speeding ticket = positive punishment.
Phone taken away = negative punishment.
Generalization vs. Discrimination (Classical)
Generalization. Similar stimuli trigger the CR. Dog salivates to bell AND to doorbell (similar sound).
Discrimination. Only the exact CS triggers the CR. Dog learns to salivate only to the feeding bell, not the doorbell.
Key distinction: generalization = broader response. Discrimination = narrower response. Both are adaptive.
Extinction vs. Spontaneous Recovery vs. Extinction Burst
Extinction. CS stops triggering CR because pairings stop. Dog stops salivating to bell when bell no longer predicts food.
Spontaneous recovery. After extinction + rest period, CS briefly triggers a weak CR again. Not permanent.
Extinction burst. Temporary SPIKE in the target behavior when reinforcement first stops. Tantrums get worse before they fade.
Key distinction: extinction = decline over repeated trials. Spontaneous recovery = brief return after rest. Extinction burst = short-term spike at the start of extinction.
Primary vs. Secondary Reinforcers
Primary. Innately satisfying. Food, water, warmth, sex. Don’t need to be learned.
Secondary. Acquire value by pairing with primary reinforcers. Money, praise, tokens, grades.
Key distinction: does the organism innately want it? If yes, primary. If it’s valuable only because of association, secondary.
Fixed vs. Variable, Ratio vs. Interval
Ratio (count). Reinforcement after a number of RESPONSES.
Interval (time). Reinforcement after a period of TIME.
Fixed. Same number/time every reward.
Variable. Unpredictable number/time.
Crossed:
Fixed
Variable
Ratio (count)
FR: Every 10th widget
VR: Slot machine
Interval (time)
FI: Biweekly paycheck
VI: Email arrival
Key distinction: VR (variable ratio) produces the highest, most consistent response rate and greatest resistance to extinction. That’s why gambling is so addictive.
Shaping vs. Chaining
Shaping. Reinforcing SUCCESSIVE APPROXIMATIONS to a target behavior. Teach a pigeon to peck by first rewarding facing the button, then approaching it, then touching it, finally pecking it.
Chaining. Linking already-learned individual responses into a SEQUENCE. Dance routines, driving a stick shift.
Key distinction: shaping = building a new behavior in stages. Chaining = stitching mastered pieces into a sequence.
Escape vs. Avoidance Learning
Escape. Aversive stimulus already HAPPENING; you learn a response that ENDS it. Rat learns to jump off the electric grid once shocked.
Avoidance. Signal warns BEFORE the aversive stimulus; you learn a response that PREVENTS it. Rat hears buzzer, jumps over wall, avoids shock entirely.
Key distinction: escape = reactive (stimulus is there). Avoidance = proactive (stimulus is predicted). Avoidance is notoriously hard to extinguish because the aversive stimulus never actually arrives.
Habituation vs. Sensitization (Non-Associative Learning)
Habituation. DECREASED response to a repeated harmless stimulus. You stop noticing the AC hum.
Sensitization. INCREASED response to a repeated stimulus, usually after an intense/threatening one. Startle at any sound after a trauma.
Key distinction: habituation = tuning out. Sensitization = amping up. Both involve repetition; they differ in the direction of the response change.
Habituation vs. Sensory Adaptation
Habituation. Brain-level. Receptor still fires; brain filters it out.
Key distinction: covered above too - same distinction worth repeating. Receptor fatigue = adaptation. Brain dismissal = habituation.
Insight vs. Trial-and-Error vs. Algorithm vs. Heuristic
Insight. “Aha!” moment. Sudden solution after a period of thought or rest.
Trial-and-error. Random attempts; no memory of what’s been tried.
Algorithm. Step-by-step procedure guaranteed to find the solution (exhaustive).
Heuristic. Mental shortcut that usually but not always works.
Key distinction: algorithm = systematic and guaranteed. Heuristic = fast but fallible. Insight = sudden realization. Trial-and-error = brute force without learning.
Positive Reinforcement vs. Bribery
Both involve adding something to increase behavior, but:
Positive reinforcement. Given AFTER the desired behavior to make it more likely.
Bribery. Given BEFORE or DURING the behavior, often to stop unwanted behavior.
Key distinction: timing. Reinforcement follows. Bribery precedes. This is a subtle but testable point.
Instinctive Drift vs. Biological Preparedness
Instinctive drift. Trained operant behaviors revert to INSTINCTIVE species-specific behaviors. Raccoon drops token → starts washing it (food-washing instinct).
Biological preparedness. Some stimulus-response pairs are EASIER to learn due to evolutionary relevance. Taste-illness pair learns in one trial; taste-shock doesn’t.
Key distinction: instinctive drift = trained behavior collapsing into instinct. Preparedness = some pairings are easier to train in the first place. Both show biology shapes what and how fast animals learn.
Short-term memory. Traditional term - temporary storage for ~20-30 seconds, ~7 ± 2 items.
Working memory. The more modern concept - Baddeley’s multi-component model including phonological loop, visuospatial sketchpad, central executive, and episodic buffer. Actively PROCESSES info, not just holds it.
Key distinction: STM is passive storage. Working memory is active manipulation. In practice, MCAT uses both terms loosely but working memory is the current preferred framework.
Semantic. General knowledge and facts. “Paris is in France.” Explicit.
Procedural. How to do things. “Riding a bike.” Implicit. Stored in basal ganglia + cerebellum.
Key distinction: episodic = personal events. Semantic = general facts. Procedural = motor skills. First two are explicit; last is implicit.
Retrograde vs. Anterograde Amnesia
Retrograde. Loss of memories BEFORE the injury. “Retro = back.”
Anterograde. Inability to form NEW memories AFTER the injury. “Antero = forward.”
Key distinction: direction of memory loss. Hippocampus damage → anterograde (can’t make new). Concussion often → retrograde (loses recent).
Proactive vs. Retroactive Interference
Proactive. OLD info disrupts NEW learning. Old password keeps interfering with new one.
Retroactive. NEW info disrupts OLD memory. New address makes old address harder to recall.
Key distinction: proactive “pushes forward” from old. Retroactive “reaches back” into old. Same direction as the prefixes.
Alzheimer’s vs. Korsakoff’s Syndrome
Alzheimer’s. Progressive. Amyloid plaques + tau tangles. Short-term memory affected first. Cholinergic neuron loss → cholinesterase inhibitors help.
Korsakoff’s. Caused by thiamine (B1) deficiency, usually chronic alcoholism. Preceded by Wernicke’s encephalopathy. Severe memory loss with CONFABULATION (making up stories). Not progressive if treated.
Key distinction: Alzheimer’s progresses. Korsakoff’s can stabilize with thiamine. Alzheimer’s has plaques/tangles; Korsakoff’s has vitamin deficiency. Korsakoff’s signature: confabulation.
Delirium. Acute, sudden, often reversible confusion. Triggered by infection, medication, drug withdrawal, metabolic issues.
Key distinction: dementia = slow, lasting. Delirium = fast, often reversible. Elderly patients with acute confusion in a hospital are almost always delirious, not newly demented.
Serial Position Effect: Primacy vs. Recency
Primacy. Better recall of items EARLY in a list. They had more rehearsal time → moved to LTM.
Recency. Better recall of items LATE in a list. Still in working memory.
Key distinction: primacy = LTM mechanism. Recency = working memory mechanism. A delay between list and recall wipes out recency (still working memory) but not primacy (already in LTM).
Assimilation vs. Accommodation (Piaget)
Assimilation. Fitting new info into EXISTING schema. Child sees a wolf, calls it a “dog” (fits into dog schema).
Accommodation. MODIFYING schemas to fit new info. Child learns “that’s a different kind of animal called a wolf” (splits schema).
Key distinction: assimilation keeps schema. Accommodation changes schema. Both happen constantly as children (and adults) learn.
Availability vs. Representativeness Heuristic
Availability. Judging probability by how easily EXAMPLES come to mind. “Plane crashes seem scary because of news coverage.”
Representativeness. Judging probability by how well something matches a PROTOTYPE. “Linda sounds like a feminist, so she’s probably a feminist bank teller” (conjunction fallacy).
Key distinction: availability uses specific memories. Representativeness uses category match. Availability = “I can think of examples.” Representativeness = “It fits the type.”
Fluid vs. Crystallized Intelligence
Fluid. Abstract reasoning on NOVEL problems. Peaks in early adulthood, then DECLINES.
Crystallized. Accumulated knowledge, vocabulary, experience. STABLE or IMPROVES through middle age.
Key distinction: fluid declines; crystallized doesn’t. Older adults compensate by using crystallized knowledge to offset fluid decline.
Broca’s vs. Wernicke’s Aphasia
Broca’s (nonfluent/expressive). Frontal lobe lesion. Labored, broken speech. Comprehension PRESERVED. Patient often frustrated because they know what they want to say.
Wernicke’s (fluent/receptive). Temporal lobe lesion. Fluent but NONSENSICAL speech (“word salad”). Comprehension IMPAIRED. Patient often unaware their speech doesn’t make sense.
Conduction aphasia. Damage to ARCUATE FASCICULUS (connecting Wernicke’s to Broca’s). Speech fluent, comprehension OK, but CAN’T REPEAT what they just heard.
Global aphasia. BOTH Broca’s and Wernicke’s damaged. Severely impaired production and comprehension.
Key distinction: conduction = production and comprehension work, but repetition fails. Global = everything impaired.
Linguistic Relativism vs. Determinism
Relativism (weak Whorfian). Language INFLUENCES thought (makes some thoughts easier or more habitual).
Determinism (strong Whorfian). Language DETERMINES thought (you can’t think concepts you don’t have words for).
Key distinction: relativism = language nudges thought. Determinism = language forces thought. Modern linguists accept relativism but reject strong determinism.
Nativist vs. Learning vs. Interactionist (Language Development)
Nativist (Chomsky). Children born with a Language Acquisition Device. Language is innate.
Learning (Skinner). Language acquired through imitation + reinforcement. Environmental only.
Interactionist (Vygotsky). Both biology AND social interaction needed. Children are built to learn, and social interaction activates that capacity.
Key distinction: nativist = nature. Learning = nurture. Interactionist = both. Most modern researchers lean toward interactionist.
All four use the same ingredients: event, physiological response (PR), emotion. They differ on the order.
James-Lange. Event → PR → Emotion. “I feel afraid BECAUSE my heart is racing.” (Body first, then feeling.)
Cannon-Bard. Event → PR and Emotion SIMULTANEOUSLY. Heart races AND I feel fear at the same time.
Schachter-Singer (two-factor). Event → PR → COGNITIVE LABEL → Emotion. Body aroused + context tells me why = specific emotion.
Lazarus (cognitive appraisal). Event → APPRAISAL → PR and Emotion. I evaluate the event first, then my body and feelings follow.
Key distinction: order of cognition. James-Lange: no cognition needed. Cannon-Bard: cognition and PR arrive together. Schachter-Singer: cognition labels the PR. Lazarus: cognition comes first and drives everything.
Quick scenario tells:
“Heart racing then felt afraid” → James-Lange.
“Both at once” → Cannon-Bard.
“Racing heart + saw a threat = labeled as fear” → Schachter-Singer.
“Interpreted the situation as threatening first” → Lazarus.
Stress vs. Stressor vs. Stress Reaction
Stress. The overall process.
Stressor. The triggering event (deadline, loud noise, threat).
Stress reaction. Your body/mind’s response to the stressor.
Key distinction: stress = the whole interaction. Stressor = what’s doing the stressing. Stress reaction = your response.
Primary vs. Secondary Appraisal (Lazarus)
Primary appraisal. Is this event RELEVANT or STRESSFUL? Irrelevant / benign / stressful.
Secondary appraisal. Can I COPE? Evaluate harm, threat, challenge.
Key distinction: primary = is it a problem? Secondary = can I handle it? Only stressful events trigger secondary appraisal.
Eustress vs. Distress
Eustress. Positive stress. Motivating, productive. Excitement before a presentation.
Distress. Negative stress. Overwhelming, harmful. Panic before a presentation you’re unprepared for.
Key distinction: same physiology, different appraisal. Moderate stress usually helps performance (Yerkes-Dodson law).
Emotion vs. Mood
Emotion. Short-lived, intense, tied to a specific event. “I’m angry because you lied.”
Mood. Longer-lasting, less intense, less event-specific. “I’ve felt down all week.”
Key distinction: emotion = quick and specific. Mood = slow and diffuse.
Adrenal Medulla vs. Adrenal Cortex
Medulla (inner). Releases EPINEPHRINE and NOREPINEPHRINE. Fast sympathetic response (fight-or-flight).
Cortex (outer). Releases CORTISOL and other steroids. Slower, sustained HPA-axis response.
Key distinction: medulla = fast. Cortex = slow. “COrtisol from the CORTex.”
Sympathetic vs. Parasympathetic
Sympathetic. Fight or flight. HR up, pupils dilate, digestion down, salivation down, blood to muscles.
Key distinction: id wants pleasure NOW, superego wants perfection, ego negotiates. Strong ego = healthy. Weak ego = impulsive (id dominates) or guilt-ridden (superego dominates).
Drive-Reduction vs. Incentive vs. Arousal Theories of Motivation
Drive-reduction. Behavior motivated by NEED (deprivation creates drive; satisfying drive returns to homeostasis). Hunger motivates eating.
Incentive. Behavior motivated by EXTERNAL REWARDS (money, status, praise). Work extra hours for a bonus.
Optimum arousal. Behavior motivated to reach OPTIMAL AROUSAL level. Seek stimulation when bored, seek quiet when overwhelmed.
Key distinction: drive-reduction = push from inside. Incentive = pull from outside. Arousal = seeking just-right stimulation.
Intrinsic vs. Extrinsic Motivation
Intrinsic. INTERNAL satisfaction drives the behavior. You play piano because you love it.
Extrinsic. EXTERNAL rewards drive the behavior. You play piano because your parents pay you.
Key distinction: is the motivation inside you or outside? Extrinsic rewards for previously intrinsic activities can REDUCE intrinsic motivation (overjustification effect).
Growth needs. Self-actualization. Always motivating, even when lower needs are met.
Key distinction: deficiency needs are felt when lacking. Growth needs are ongoing. Without lower needs met, higher needs don’t motivate (starving students don’t pursue self-actualization).
Instincts vs. Drives
Instincts. Innate, species-wide behavioral patterns. Baby turning to nipple. Genetic.
Drives. Internal tension from physiological need. Thirst, hunger. Can vary with learning.
Key distinction: instincts are fixed programs. Drives are signals of need that behavior can satisfy. Drive-reduction theory relies on drives, not instincts.
Cognitive Dissonance vs. Self-Perception
Cognitive dissonance (Festinger). Discomfort when beliefs and behavior conflict. Resolved by changing one.
Self-perception (Bem). We learn our attitudes BY OBSERVING our own behavior. If I volunteer, I conclude “I must care about this cause.”
Key distinction: dissonance requires discomfort (I behaved against my beliefs, now I’m uncomfortable). Self-perception is neutral (I observe my own behavior to infer my attitude). Both predict attitude change from behavior, but differ in mechanism.
Foot-in-the-Door vs. Door-in-the-Face
Foot-in-the-door. Small request first, then larger request. Small “yes” shifts self-image toward agreeable.
Door-in-the-face. Large outrageous request first, then the real (smaller) request. The contrast makes the target look reasonable.
Key distinction: foot-in-the-door starts small. Door-in-the-face starts outrageously big. Both exploit human psychology to increase compliance.
Central vs. Peripheral Route of Persuasion (ELM)
Central route. Deep processing. Quality of the argument matters. Produces LASTING attitude change.
Peripheral route. Surface processing. Cues like attractiveness, expert badges, or number of arguments drive persuasion. Produces TEMPORARY change.
Key distinction: central = thinks hard about the content. Peripheral = influenced by superficial cues. Listener motivation and ability determine which route activates.
Key distinction: four distinct pathways, four different jobs. Don’t confuse mesolimbic (reward) with mesocortical (cognition) - they’re opposite ends of the schizophrenia picture.
Acetylcholine: CNS vs. PNS
CNS. Basal forebrain → cortex. Attention, memory. Declines in ALZHEIMER’S.
PNS. All motor neurons at neuromuscular junction. All parasympathetic postganglionic synapses. All preganglionic sympathetic and parasympathetic.
Key distinction: acetylcholine is everywhere in the PNS. In the CNS it specifically matters for attention/memory.
fMRI. Blood oxygenation (BOLD). Best SPATIAL resolution for function. Moderate temporal.
Key distinction: if you need anatomy → MRI or CT. If you need millisecond timing → EEG. If you need precise location of activity → fMRI. If you need metabolic activity → PET.
Gyrus vs. Sulcus
Gyrus. RIDGE of the cortex (the bump).
Sulcus. GROOVE of the cortex (the valley).
Key distinction: gyri stick out; sulci dip in. Deep sulci are fissures (central fissure divides frontal and parietal lobes).
Social cognitive (Bandura). Personality = interaction of behavior, cognition, environment. Reciprocal determinism.
Trait theory. Personality = stable traits. Allport, Cattell (16 PF), Eysenck (PEN), Big Five (OCEAN).
Key distinction: where does personality come from?
Psychoanalytic = unconscious conflicts.
Humanistic = self-actualization drive.
Biological = genes/brain.
Behaviorist = environment.
Social cognitive = interaction of all three.
Trait = stable dispositions (descriptive, not causal).
OCD vs. OCPD (The Classic MCAT Trap)
OCD (Obsessive-Compulsive Disorder). Obsessions (intrusive unwanted thoughts) + compulsions (behaviors to neutralize). EGO-DYSTONIC - the person finds the symptoms distressing and irrational.
OCPD (Obsessive-Compulsive Personality Disorder). Pervasive pattern of perfectionism, rigidity, control. EGO-SYNTONIC - the person thinks their way is correct.
Key distinction: OCD sufferers want to stop; OCPD sufferers don’t see a problem. OCD is an anxiety-related disorder. OCPD is a personality disorder (Cluster C).
DID vs. Schizophrenia (Another Classic Confusion)
Dissociative identity disorder. MULTIPLE distinct personality states take control. Memory gaps between states. Linked to severe childhood trauma. One person has multiple “alters.”
Schizophrenia. ONE identity, but with hallucinations, delusions, disorganized thought. Psychotic disorder. Not related to “split personality.”
Key distinction: DID = multiple identities. Schizophrenia = broken thought/perception within one identity. Popular culture confuses them constantly; the MCAT does not.
Somatic Symptom Disorder vs. Conversion vs. Illness Anxiety vs. Factitious vs. Malingering
Somatic symptom disorder. Real distressing physical symptoms + excessive worry about them. Symptoms may or may not have medical basis.
Conversion (functional neurological symptom) disorder. Neurological symptoms (blindness, paralysis) with NO medical basis. Not conscious.
Illness anxiety disorder. Preoccupation with having/getting an illness. Few or no actual symptoms.
Factitious disorder. Intentionally producing/faking symptoms to assume the SICK ROLE (internal motivation).
Malingering. Intentionally faking symptoms for EXTERNAL GAIN (money, drugs, avoiding work). NOT a mental disorder - it’s deception.
Key distinctions:
Real symptoms + real worry → somatic symptom disorder.
Neurological signs with no cause → conversion.
Fear of illness with few symptoms → illness anxiety disorder.
Intentional faking for sick role → factitious.
Intentional faking for external reward → malingering.
Bipolar I vs. Bipolar II vs. Cyclothymic
Bipolar I. At least ONE manic episode (lasting ≥1 week). Depression common but not required.
Bipolar II. At least one hypomanic episode (≥4 days, less severe than mania) + at least one major depressive episode. NO full manic episode.
Cyclothymic disorder. Chronic (≥2 years) alternation of hypomanic and depressive symptoms, not meeting full episode criteria.
Key distinction: Bipolar I requires full MANIA. Bipolar II requires hypomania + depression. Cyclothymic is a milder, chronic version. One full manic episode upgrades bipolar II to bipolar I.
MDD vs. Persistent Depressive Disorder (Dysthymia)
MDD. Episodic. ≥5 symptoms for ≥2 weeks. Severe impairment.
Persistent depressive disorder. Chronic (≥2 years, 1 year in children). Less severe than MDD. Low-grade but continuous.
Key distinction: MDD = severe episode. PDD = chronic low-grade. “Double depression” is when MDD episodes occur on top of PDD.
Negative. SUBTRACTIONS. Flat affect, avolition, alogia, anhedonia, social withdrawal.
Key distinction: positive adds; negative takes away. Positive symptoms respond better to antipsychotics; negative symptoms are harder to treat.
Typical vs. Atypical Antipsychotics
Typical (first-generation). Haloperidol, chlorpromazine. D2 receptor blockers. Effective for positive symptoms, cause movement side effects (tardive dyskinesia).
Atypical (second-generation). Risperidone, olanzapine, clozapine. D2 + serotonin receptor blockers. Better for negative symptoms, fewer movement side effects, but metabolic risks.
Key distinction: typicals block dopamine aggressively → movement problems. Atypicals hit serotonin too → fewer movement side effects but weight gain and metabolic issues. Clozapine is most effective but risks agranulocytosis.
The Ten Personality Disorders (Three Clusters)
Cluster A (“odd or eccentric”). Paranoid, schizoid, schizotypal.
Cluster B (“dramatic, emotional, erratic”). Antisocial, borderline, histrionic, narcissistic.
Cluster C (“anxious or fearful”). Avoidant, dependent, obsessive-compulsive personality (OCPD).
Key distinction:
A = weird (paranoid, loner, magical thinking).
B = wild (antisocial, unstable, dramatic, grandiose).
C = worried (avoidant, dependent, perfectionist).
Schizoid vs. Schizotypal vs. Schizophrenia
Schizoid. Cluster A personality disorder. Detached from social life by PREFERENCE. Not psychotic. “A loner who wants to be alone.”
Schizotypal. Cluster A personality disorder. Eccentric thinking, magical beliefs, odd speech. Milder cousin of schizophrenia but not psychotic.
Schizophrenia. Actual psychotic disorder. Hallucinations, delusions, disorganized thought.
Each a CRISIS between two poles, across the full lifespan:
Trust vs. mistrust (0-1).
Autonomy vs. shame/doubt (1-3).
Initiative vs. guilt (3-6).
Industry vs. inferiority (6-12).
Identity vs. role confusion (12-18).
Intimacy vs. isolation (young adult).
Generativity vs. stagnation (middle age).
Integrity vs. despair (old age).
Key distinction from Freud: Erikson spans the whole lifespan; Freud stops at adolescence. Erikson’s stages are about social/psychological development, not sexual.
Conventional. Stage 3: good-boy/good-girl. Stage 4: law and order.
Postconventional. Stage 5: social contract. Stage 6: universal ethical principles.
Key distinction: preconventional = consequences for me. Conventional = following norms and laws. Postconventional = abstract principles that can override laws.
Concrete operational (7-11). Conservation, logic on real things, empathy.
Formal operational (12+). Abstract and hypothetical reasoning.
Key distinction from Freud and Erikson: Piaget is COGNITIVE (thinking). Freud is SEXUAL. Erikson is PSYCHOSOCIAL (identity and relationships). Three separate frameworks, each useful for different questions.
Vygotsky vs. Piaget
Piaget. Development driven by the child’s own discovery. Mostly self-directed.
Vygotsky. Development driven by SOCIAL interaction with more knowledgeable others. Zone of proximal development.
Key distinction: Piaget says the child explores alone. Vygotsky says the child learns through guided interaction. Modern research sees value in both.
Defense Mechanisms (The Easy-to-Confuse Set)
Repression. Unconscious forgetting of anxiety-provoking memories.
Suppression. Conscious choice to avoid thinking about something.
Denial. Refusing to acknowledge reality.
Projection. Attributing your own unacceptable feelings to others.
Displacement. Redirecting emotion to a safer target.
Conformity. Matching behavior to a PEER group. Asch’s line studies.
Obedience. Complying with an AUTHORITY figure. Milgram’s shock experiments.
Key distinction: conformity is peer-based. Obedience is hierarchical. Both are forms of social influence but operate on different axes.
Normative vs. Informational Social Influence
Normative. Going along to be ACCEPTED or avoid rejection. You know the group is wrong but don’t want to stand out.
Informational. Going along because you think the group has BETTER INFORMATION than you.
Key distinction: normative = about fitting in. Informational = about being right. Both produce conformity but via different motives.
Social Facilitation vs. Social Loafing
Social facilitation. Presence of others ENHANCES easy/well-learned tasks, IMPAIRS complex/novel tasks (via arousal).
Social loafing. In a group, individuals exert LESS effort when contributions aren’t identifiable.
Key distinction: facilitation = performance on a task changes with observers. Loafing = less effort when submerged in a group. Facilitation is about arousal; loafing is about diffused responsibility.
Deindividuation vs. Groupthink
Deindividuation. Loss of SELF-AWARENESS and accountability in a group, especially with anonymity. Leads to unrestrained behavior (mobs, rioters, online trolls).
Groupthink. Dysfunctional DECISION-MAKING in cohesive groups. Desire for harmony overrides critical evaluation. Smart people make bad group decisions.
Key distinction: deindividuation = loss of individual identity in a crowd (mob behavior). Groupthink = poor group decisions that individuals wouldn’t make alone (Bay of Pigs).
Group Polarization vs. Groupthink
Group polarization. Discussion makes a group’s initial position MORE EXTREME.
Groupthink. Group suppresses dissent and makes bad decisions.
Key distinction: polarization = becomes more extreme (both directions). Groupthink = becomes more dysfunctional. Polarization can produce groupthink but they’re distinct phenomena.
The Three Attribution Errors
Fundamental attribution error. Explaining OTHERS’ behavior with DISPOSITIONAL causes while underweighting situational causes. “She cut me off because she’s rude” (not “because she’s rushing to a hospital”).
Actor-observer bias. Explaining OTHERS’ behavior with disposition but OWN behavior with situation. “I cut you off because I was in a hurry; she cut me off because she’s rude.”
Self-serving bias. Attributing OWN successes to disposition and OWN failures to situation. “I got the A because I’m smart; I failed because the test was unfair.”
Key distinction: fundamental = others get disposition. Actor-observer = others/dispositional, self/situational. Self-serving = successes are you, failures aren’t.
Stereotype vs. Prejudice vs. Discrimination
Stereotype. Generalized BELIEF about a group (cognition).
Prejudice. Negative ATTITUDE or feeling toward a group (emotion).
Discrimination. Unequal TREATMENT based on group membership (behavior).
Key distinction: stereotype = thought. Prejudice = feeling. Discrimination = behavior. Can occur independently - you can discriminate without prejudice (via institutional policy) or hold prejudice without discriminating (keeps it to yourself).
Individual vs. Institutional Discrimination
Individual. One person treating another unequally.
Institutional. Policies, practices, or systems that produce unequal outcomes, even without any individual holding prejudice.
Key distinction: individual = one actor. Institutional = structural, often invisible. Algorithmic bias is usually institutional.
In-group vs. Out-group
In-group. Group you IDENTIFY with.
Out-group. Group you DON’T identify with.
Predictable effects:
In-group favoritism (prefer in-group members).
Out-group homogeneity (“they all look the same”).
Even arbitrary group assignment produces these.
Stereotype Threat vs. Self-Fulfilling Prophecy
Stereotype threat. A stigmatized group member’s performance is LOWERED by awareness of the stereotype. “Black students reminded of race underperform on standardized tests.”
Self-fulfilling prophecy. An expectation about someone causes BEHAVIOR that CONFIRMS the expectation. Rosenthal’s Pygmalion study: teachers told certain students were “late bloomers” unconsciously treated them differently, and those students improved more.
Key distinction: stereotype threat = the stigmatized person’s performance drops because of the stereotype. Self-fulfilling prophecy = others’ expectations cause behavior that confirms them. Both involve expectations but the mechanism differs.
Mead’s “I” vs. “Me”
“I”. The spontaneous, creative, subjective self. Initiates action.
“Me”. The internalized social self. How you perceive others see you.
Mead. Self develops through role-taking stages (preparatory → play → game). Includes “I” and “Me.”
Cooley. “Looking-glass self.” Self-concept forms from perceived judgments of others: (1) imagine how you appear, (2) imagine how others judge, (3) develop self-concept accordingly.
Key distinction: Mead’s stages describe the developmental trajectory. Cooley’s model describes the reflective mechanism. Both are symbolic interactionist - they complement each other.
Proximity vs. Similarity vs. Reciprocal Liking (Attraction)
Proximity. Physical closeness → mere exposure effect → liking.
Physical attraction. Symmetry, averageness, signs of health.
Key distinction: proximity gives opportunity (you can only like people you encounter). Similarity gives alignment. Reciprocal liking gives mutual reinforcement. Physical attraction is initial. All four contribute.
Kin Selection vs. Reciprocal Altruism
Kin selection. Favoring relatives who share your genes (Hamilton’s rule: rB > C).
Reciprocal altruism. Favoring non-relatives in stable groups who are likely to RETURN the favor.
Key distinction: kin selection relies on genetic relatedness. Reciprocal altruism relies on expected reciprocity. Both explain how altruism evolved.
Instrumental vs. Hostile Aggression
Instrumental. Aggression as a MEANS to an end. Mugger, soldier in combat.
Hostile. Aggression driven by ANGER, aimed at harming for its own sake. Rage fight.
Bystander Effect: Diffusion of Responsibility vs. Pluralistic Ignorance
Diffusion of responsibility. “Someone else will help.”
Pluralistic ignorance. “If no one else is reacting, maybe it’s not an emergency.”
Key distinction: both produce the bystander effect. Diffusion splits responsibility. Pluralistic ignorance takes cues from others’ inaction. Usually operate together.
Collective Behavior vs. Group Behavior
Group behavior. Structured, long-lasting, stable membership, well-defined norms.
Latent. UNINTENDED, unrecognized consequences. Schools latently sort students into class positions, provide babysitting, and serve as marriage markets.
Key distinction: manifest = on purpose. Latent = by-product.
Mechanical vs. Organic Solidarity (Durkheim)
Mechanical. Simple societies where people do SIMILAR work. Bonds from shared experience and values. Small, homogeneous.
Organic. Complex industrial societies where work is SPECIALIZED. Bonds from interdependence (you need the farmer, the farmer needs you). Large, heterogeneous.
Key distinction: mechanical = similarity holds it together. Organic = specialization + interdependence. Modernization shifts societies from mechanical to organic.
Ascribed vs. Achieved Status
Ascribed. Assigned at birth or without your choice. Race, sex assigned at birth, family of origin.
Achieved. Earned through effort and choice. Occupation, education, marital status.
Reference. A group you use as a STANDARD for self-evaluation. Might not be a member.
Key distinction: primary = emotional. Secondary = instrumental. Reference = standard for comparison.
In-group vs. Out-group vs. Aggregate vs. Category
In-group / out-group. Groups you identify with / don’t identify with.
Aggregate. People in the same place at the same time without meaningful interaction (bus stop).
Category. People sharing a characteristic without interaction (all left-handers).
Key distinction: group requires interaction/identification. Aggregates and categories are just collections.
Weber’s Three Types of Authority
Traditional. Based on LONG-ESTABLISHED customs. Monarchs, established religious leaders.
Rational-legal. Based on LAWS AND PROCEDURES. Attached to the office, not the person. Democratic governments, corporate hierarchies.
Charismatic. Based on PERSONAL MAGNETISM. Gandhi, MLK, revolutionary leaders. Unstable - must institutionalize or die with the leader.
Key distinction: traditional = “because that’s how it’s always been.” Rational-legal = “because that’s the rule.” Charismatic = “because of who they are.”
Ethnocentrism vs. Cultural Relativism
Ethnocentrism. Judging others’ cultures by YOUR OWN standards.
Cultural relativism. Judging a culture WITHIN ITS OWN context without outside standards.
Key distinction: ethnocentrism is your default bias; cultural relativism is an anthropologist’s trained stance.
Cultural Lag vs. Cultural Shock
Cultural lag. Material culture (technology) changes FASTER than non-material culture (norms, laws). Internet outpaced privacy laws.
Cultural shock. The DISORIENTATION of encountering a very different culture. Phases: honeymoon, frustration, adjustment, mastery.
Key distinction: lag = norms catching up to tech. Shock = individual adjusting to new culture.
Subculture vs. Counterculture
Subculture. Distinct norms/values within the broader culture, but NOT in opposition. Gamers, medical students, biker clubs.
Counterculture. Actively REJECTS and opposes the dominant culture’s values. 1960s hippies, militant separatists.
Key distinction: subculture = distinct. Counterculture = distinct AND oppositional.
Taboos. Deep moral prohibitions. Violation = “disgusting.” Incest, cannibalism.
Laws. Formal norms with institutional enforcement. Often codify mores.
Key distinction: folkways (odd) → mores (wrong) → taboos (disgusting). Severity rises. Laws are formal rules backed by the state.
Primary vs. Secondary Deviance
Primary. Initial norm violation that doesn’t alter self-image.
Secondary. Amplified deviance in response to being LABELED a deviant.
Key distinction: primary = initial act. Secondary = label-driven amplification. Labeling theory connects the two.
Differential Association vs. Labeling Theory vs. Strain Theory
Differential association (Sutherland). Deviance is LEARNED through association with deviant peers.
Labeling (Lemert, Becker). Social REACTION to deviance creates more deviance (primary → secondary).
Strain (Merton). Deviance results when cultural goals are unreachable through legitimate means. Five responses: conformity, innovation, ritualism, retreatism, rebellion.
Key distinction:
Learned from associates → differential association.
Label drives further deviance → labeling.
Blocked access to goals → strain.
Absolute vs. Relative Poverty
Absolute. Lacking resources for BASIC NEEDS (food, shelter, water, healthcare). World Bank extreme poverty line: <$2.15/day.
Relative. Having significantly LESS than the MEDIAN in one’s society.
Key distinction: absolute is objective. Relative is comparative. A family “poor” in the US may have more absolute resources than a middle-class family in some developing countries, but still faces exclusion from their society’s mainstream.
Types of Social Mobility
Intergenerational. Position RELATIVE TO YOUR PARENTS.
Intragenerational. YOUR OWN position across YOUR LIFE.
Vertical. Between social classes.
Horizontal. Within the same class (different job, same rank).
Structural. Large-scale mobility due to ECONOMIC CHANGES, not individual merit.
Upward. Moving up.
Downward. Moving down.
Key distinction: who moves and why. Intergenerational compares to parents. Intragenerational compares to your past self. Structural affects groups due to economic shifts.
Capitalism vs. Socialism vs. Mixed Economy
Capitalism. PRIVATE ownership of means of production. Market-based distribution.
