1,800+ MCAT terms, defined.

In Freud's psychoanalytic theory, the ego is the part of personality that follows the reality principle, mediating between the id's urges and the superego's moral standards. On the MCAT, the ego is the realistic mediator and the user of...

Endorphins are neuropeptides the body makes that act like opioids, binding opioid receptors to reduce pain and produce feelings of pleasure or well-being. The MCAT links them to pain modulation, stress, exercise, and the reward effects o...

Source monitoring is the process of deciding where a memory came from: who told you, where you saw it, or whether you imagined it. Its failures, called source monitoring errors or source misattribution, are a testable reason memory is re...

A threshold is the minimum stimulus intensity needed to produce a response. In sensation, the absolute threshold is the weakest stimulus detected about 50% of the time, and the difference threshold is the smallest change noticed about 50...

Parkinson's disease is a progressive neurodegenerative disorder in which dopamine-producing neurons of the substantia nigra die, causing resting tremor, rigidity, and slowed movement. Most testable: it involves too little dopamine, the o...

Self-serving bias is the tendency to attribute your own successes to internal, dispositional causes and your own failures to external, situational causes. It is usually explained as protecting self-esteem. It concerns explaining your own...

A depressant is a psychoactive drug that reduces central nervous system activity, lowering arousal, anxiety and inhibition. Alcohol, barbiturates and benzodiazepines are the standard examples, and they act largely by enhancing GABA, the...

The mesolimbic pathway is a dopamine circuit running from the ventral tegmental area (VTA) in the midbrain to limbic targets, especially the nucleus accumbens. It is the core of the brain's reward system, and many addictive drugs and rew...

Language development is the sequence by which children move from cooing and babbling to words, phrases and grammatical sentences, with comprehension ahead of production. The most testable point is contrasting the learning (Skinner), nati...

Valence is the positive or negative quality of an emotion or stimulus: how pleasant or attractive versus unpleasant or aversive it is. It is separate from arousal (intensity), so the key skill is sorting emotions by valence without confu...

Concrete operational is Piaget's third stage of cognitive development, roughly ages 7 to 11, when children reason logically about concrete, real objects and events. The most testable point is conservation: they grasp that quantity stays...

Identity is a person's sense of who they are, made up of personal identity (individual traits, abilities, history) and social identity (membership in groups such as gender, race, religion or class). Identity describes the self; self-este...

Gate control theory (Melzack and Wall) says pain perception depends on a "gate" in the spinal cord's dorsal horn. Small pain-fiber input tends to open it, while large touch-fiber input and descending brain signals can close it. This is w...

Addiction is compulsive seeking and use of a substance despite harmful consequences. The MCAT ties it to the brain's dopamine reward pathway (VTA to nucleus accumbens) and to reinforcement: the drug's effect or relief of withdrawal stren...

Communication is the transfer of information from a sender to a receiver by verbal (language) and nonverbal means (expressions, gestures, eye contact, personal space). Testable point: basic facial expressions are widely recognized across...

Decision making is the cognitive process of choosing among alternatives. The MCAT contrasts slow, deliberate reasoning (weighing options, algorithms) with fast heuristics, which are mental shortcuts that are efficient but can produce sys...

In Freud's psychodynamic theory, fixation is arrested psychosexual development: unresolved conflict at a stage keeps some energy tied to it and shapes adult traits, such as oral habits. The testable point is matching a behavior to its st...

A taste bud is a cluster of gustatory receptor cells, which are chemoreceptors that transduce dissolved chemicals into neural signals. They sit mostly in tongue papillae and detect sweet, sour, salty, bitter and umami. The exam often tes...

Anchoring bias is the tendency to rely too heavily on the first piece of information (the anchor) when making a judgment, so later estimates stay close to it. The testable point: adjustment away from the anchor is usually insufficient, e...

Working memory is the limited-capacity system that holds and manipulates information for seconds while a task is carried out. The MCAT ties it to Baddeley's model (a central executive plus subsystems) and to a capacity of about 7 ± 2 ite...

Attribution is the process of explaining the causes of behavior, either as dispositional (internal traits, ability, effort) or situational (external circumstances, luck). The most testable point is that observers often overweight disposi...

Top-down processing is perception guided by prior knowledge, expectations, and context, which shape how sensory input is interpreted. It contrasts with bottom-up processing, which builds a percept from the stimulus features. Expect it to...

The pons is a hindbrain and brainstem structure between the medulla and midbrain. It relays signals between the cerebrum and cerebellum and helps regulate sleep and arousal, including REM sleep. Most testable: it belongs to the hindbrain...

Heuristics are mental shortcuts, or rules of thumb, that let people judge or solve problems quickly with little effort. They often give good answers but can produce systematic errors, unlike an algorithm, a step-by-step procedure that gi...

Extinction is the weakening of a learned response when the conditioned stimulus appears without the unconditioned stimulus (classical) or when a behavior is no longer reinforced (operant). It suppresses learning rather than erasing it, s...

Observational learning is acquiring a behavior by watching a model and the consequences the model receives, without being directly reinforced yourself. In Bandura's Bobo doll study, children imitated aggression more when the model was re...

Solomon Asch's studies showed that people often go along with a unanimous group's clearly wrong answer on a simple line-matching task. It is the classic demonstration of conformity driven by normative social influence, and one dissenter...

Kohlberg proposed that moral reasoning develops in a fixed order through three levels (preconventional, conventional, postconventional), each with two stages. The most testable point is that the stage is set by the reasoning a person giv...

Milgram's obedience experiment showed that many ordinary people (about 65% in the baseline version) would deliver what they believed were severe shocks to another person when an authority figure told them to. The testable point: obedienc...

Wernicke's aphasia is a language disorder caused by damage to Wernicke's area, usually in the left temporal lobe. Comprehension is impaired, and speech is fluent but often meaningless. The testable contrast is Broca's aphasia, where spee...

Sensation is the detection of physical or chemical stimuli by sensory receptors and their transduction into neural signals sent to the brain. It comes before perception, which is the brain's interpretation of that input, and the MCAT oft...

Wernicke's area is a region of the temporal lobe, usually in the left hemisphere, involved in understanding spoken and written language. Damage causes Wernicke's (receptive) aphasia: speech is fluent but often meaningless, and comprehens...

Maslow's hierarchy of needs is a humanistic theory of motivation that ranks needs from physiological and safety up through love and belonging, esteem, and self-actualization. Lower needs generally must be largely met before higher ones d...

Situational attribution (external attribution) explains a person's behavior by outside factors such as circumstances, luck, or other people, not by traits. The testable point is that observers underuse it for others' behavior (fundamenta...

A sensory receptor is a specialized cell or nerve ending that detects a type of stimulus and converts it into a neural signal (sensory transduction). Testable point: receptor type sets which stimulus is detected, and the brain area recei...

Neuroticism is the Big Five (five-factor) trait describing a tendency toward negative emotions such as anxiety, worry, and moodiness, with strong reactions to stress. The low end is emotional stability. It is a normal-range personality d...

Adoption studies compare adopted children with their biological relatives and their adoptive relatives to separate genetic from environmental influence on a trait. Greater resemblance to biological parents suggests heredity; greater rese...

An instinct is an innate, unlearned, species-typical behavior pattern triggered by a specific stimulus. In the instinct theory of motivation, behavior comes from inherited programming rather than learning, but the theory mostly labels be...

Broca's area is a region of the frontal lobe, in the left hemisphere for most people, that supports speech production and grammar. Damage causes Broca's (expressive, nonfluent) aphasia: effortful, halting speech with comprehension largel...

Drive-reduction theory says a physiological need (like hunger) creates an unpleasant drive that pushes behavior aimed at reducing it and restoring homeostasis. Its testable weakness is that it does not easily explain behaviors that raise...

Identification is changing your attitudes or behavior to resemble a person or group you admire or want to belong to. It is one of Kelman's three processes of social influence. The testable point: it tends to last only as long as the bond...

The olfactory bulb is the brain structure that receives smell signals from receptor neurons in the nasal lining and sends them on to olfactory cortex and limbic areas. Unlike most other senses, smell does not need a thalamic relay first.

Wernicke's encephalopathy is an acute brain disorder caused by thiamine (vitamin B1) deficiency, most often in chronic alcohol use. It causes confusion, unsteady gait and abnormal eye movements, and often progresses to Korsakoff syndrome...

In attribution theory (Kelley's covariation model), consensus is the extent to which other people respond the same way as the actor in the same situation. High consensus points toward a situational attribution; low consensus points towar...

Deindividuation is a loss of self-awareness and personal accountability when a person is in a group or anonymous, so behavior often departs from usual standards. The classic account stresses lost self-awareness; the social identity view...

Lev Vygotsky proposed a sociocultural theory of cognitive development: learning is driven by social interaction and culture, and language is the main tool of thought. Most testable: the zone of proximal development, the gap between what...

Carl Rogers was a humanistic psychologist who developed person-centered therapy, in which the therapist offers empathy, genuineness, and unconditional positive regard to support growth toward self-actualization. Most testable: a gap betw...

Sigmund Freud founded psychoanalysis, the psychodynamic view that behavior is shaped by unconscious conflict among the id, ego, and superego. The most testable points are identifying his defense mechanisms in a vignette and knowing his p...

Formal operational is Piaget's last stage of cognitive development, starting around age 11 or 12, when a person can reason abstractly and hypothetically and test ideas systematically. Key contrast: concrete operational logic is tied to r...

Long-term memory is the relatively lasting store of information, with a very large capacity. It divides into explicit (episodic, semantic) and implicit (procedural, priming, conditioning) memory. Testable: elaborative rehearsal helps mov...