1,800+ MCAT terms, defined.

Quasi-experimental design is a research-methods term from psychology and sociology, not physics. It compares groups exposed to different conditions without random assignment, so the groups may differ beforehand. It supports weaker causal...

Body language is nonverbal communication through posture, gestures, facial expressions, eye contact, touch, and use of space. Facial expressions of basic emotions are widely recognized across cultures, but gestures and display rules vary...

C fibers are slow, unmyelinated, small-diameter sensory neurons that carry dull, aching, burning, lingering pain, often called second pain. They contrast with thinly myelinated A-delta fibers, which carry fast, sharp first pain.

Episodic memory is explicit (declarative) long-term memory for personal experiences tied to a particular time and place, such as your last birthday. The MCAT contrasts it with semantic memory, which stores general facts and meanings with...

A mood disorder is a psychological disorder defined by a prolonged disturbance of emotional state that impairs functioning. The two families are depressive disorders and bipolar disorders. Most testable: bipolar disorders require a manic...

Solomon Asch was a social psychologist whose line-judgment experiments showed conformity: people often gave an obviously wrong answer to match a unanimous group. The most testable point is that conformity drops sharply when even one othe...

Amotivation is a state of having no intention to act: the person is neither intrinsically nor extrinsically motivated. In self-determination theory it sits at the low end of the motivation continuum. It is usually tied to feeling incompe...

Fazio's model says an attitude can influence behavior without deliberate thought: it is activated from memory, shapes how you perceive the situation (along with social norms), and that perception guides action. The theory of planned beha...

Chunking is an encoding strategy that groups separate items into larger meaningful units so more information fits in working memory. The limit applies to the number of chunks (classically about 7 ± 2), so grouping raises how much is held...

Cognitive development is the change in thinking, language, and problem solving from infancy onward. The MCAT centers on Piaget's four stages (sensorimotor, preoperational, concrete operational, formal operational), with Vygotsky's social...

Counterconditioning is a classical-conditioning method that replaces an unwanted conditioned response with a new, incompatible one by pairing the stimulus with something that triggers the new response. It underlies systematic desensitiza...

In Freud's later dual-instinct theory, Eros is the life instinct: the drive toward survival, pleasure, sexuality, and creation, powered by libido. It is paired with Thanatos, the death instinct, and the exam tests telling the two apart.

Morphology is the study of how words are built from morphemes, the smallest units of language that carry meaning (such as un-, happy, -ness). The most testable point: a morpheme is not a phoneme, because phonemes are sound units that car...

Pragmatics is the component of language concerned with how context, social norms, and nonverbal cues shape meaning beyond the literal words, such as sarcasm, indirect requests, and turn-taking. Testable point: it differs from semantics (...

A prodrome is the early period of subtle, milder changes that comes before the full symptoms of a disorder appear. On the MCAT it is most often tied to schizophrenia, where social withdrawal, odd beliefs and declining functioning can pre...

Rhodopsin is the light-sensitive pigment in the rods of the retina, made of the protein opsin bound to retinal (from vitamin A). It supports vision in dim light. Light hyperpolarizes the rod, so it releases less glutamate, and rhodopsin...

Thanatos is the death instinct in Freud's psychoanalytic theory, an unconscious drive toward aggression, destruction, and, when turned inward, self-destructive behavior. It is paired with Eros, the life instinct. Testable point: both ari...

Alertness is the waking state of consciousness in which a person is responsive to the environment and able to focus attention. On an EEG it appears mainly as beta waves (high frequency, low amplitude), and the reticular formation helps m...

The blind spot is the optic disc, where the optic nerve leaves the retina. It has no rods or cones, so light falling on it is not detected. We usually do not notice it because the other eye covers the gap and the brain fills in the missi...

Psychoanalytic theory, developed by Freud, holds that behavior and personality are shaped largely by unconscious drives and by conflicts, especially from early childhood. The id, ego, and superego conflict, and the ego uses defense mecha...

Subjective norms are a person's perception of whether important others approve or disapprove of a behavior, weighed by how much the person wants to comply. In the theory of planned behavior they combine with attitude and perceived behavi...

Dissociation is a disruption in the normal integration of consciousness, memory, identity, or perception, often tied to trauma or severe stress. It underlies dissociative amnesia, dissociative identity disorder, and depersonalization/der...

Broadbent's early selection theory holds that attention acts as a filter early in processing, passing one channel on physical features like pitch or location before meaning is analyzed. Hearing your own name in an ignored conversation is...

In Piaget's theory, the formal operational stage is the last stage of cognitive development, typically beginning around age 12. Thinking becomes abstract, hypothetical and systematic. Concrete operational children reason logically only a...

The gambler's fallacy is the mistaken belief that after a streak of one outcome in independent random events, the opposite outcome is now "due." Each trial is independent, so the probability does not change. It is often explained by the...

The middle ear is the air-filled chamber between the eardrum and the cochlea's oval window. Its ossicles (malleus, incus, stapes) carry and amplify sound vibrations from air to cochlear fluid. Testable point: it conducts sound; transduct...

Retinal means "of the retina," the light-sensitive layer at the back of the eye that holds the rods and cones. The most testable use is retinal disparity: the slight difference between the two eyes' images, a binocular depth cue that is...

A semantic network is a model of long-term memory in which concepts are nodes joined by associative links. Activating one node spreads activation to linked nodes, so related concepts are retrieved faster, which is the basis of priming.

Treisman's attenuation theory is a model of selective attention in which an early filter weakens unattended input instead of blocking it. Highly meaningful stimuli, such as your own name, have low thresholds and can still break through....

VTA is the ventral tegmental area, a midbrain region whose dopamine-releasing neurons project to the nucleus accumbens and prefrontal cortex (the mesolimbic and mesocortical pathways). It is a core part of the reward pathway, and drugs o...

Correspondent inference theory (Jones and Davis) explains when observers conclude that someone's behavior reflects a matching underlying trait. Inference is strongest when the act was freely chosen, intended, and unexpected or socially u...

Endogenous means produced or driven from within the organism, as opposed to exogenous, which comes from the external environment. The MCAT uses it for endogenous opioids (endorphins), internally generated circadian rhythms, and voluntary...

In Freudian psychoanalytic theory, the pleasure principle is the id's drive to seek immediate gratification of urges and avoid tension or pain, without regard for reality or morality. The testable point: the id follows the pleasure princ...

The primary auditory cortex is the region of the temporal lobe (Heschl's gyrus) that first receives sound information from the thalamus, specifically the medial geniculate nucleus. It is organized tonotopically, so different pitches map...

Slow-wave sleep is the deepest stage of non-REM sleep (stage N3, formerly stages 3 and 4), marked by high-amplitude, low-frequency delta waves. It is the stage from which a sleeper is hardest to wake, and it is most abundant early in the...

A negative control is a group or condition that does not get the active manipulation, such as a placebo or no-treatment group, and is expected to show no effect. If it changes anyway, something other than the independent variable is infl...

Post-conventional is the third and highest level of Kohlberg's moral development. Right and wrong are judged by abstract, self-chosen principles such as justice and human rights, which can override laws and social norms. The exam scores...

The sympathetic nervous system is the division of the autonomic nervous system that mobilizes the body for threat or exertion ("fight or flight"). Heart rate, breathing, and alertness rise while digestion slows. It generally opposes the...

Depth cues are visual signals the brain uses to judge distance and three-dimensional layout from the retinal image. They are binocular (need both eyes, e.g., retinal disparity, convergence) or monocular (work with one eye, e.g., linear p...

Erikson's theory of psychosocial development describes eight lifespan stages, each built around a social crisis between a positive and a negative outcome, such as trust vs mistrust. The most testable point is matching a described behavio...

Memory errors are lapses of forgetting (failed encoding, decay, interference, retrieval failure) and distortions from reconstructive recall, such as the misinformation effect. Most testable: proactive interference is old material impairi...

The parasympathetic nervous system is the branch of the autonomic nervous system that dominates in calm conditions ("rest and digest"). It slows heart rate, constricts the pupils and promotes digestion, generally opposing the sympathetic...

A binocular cue is a depth cue that needs both eyes. The two main ones are retinal (binocular) disparity, the slight difference between the two retinal images, and convergence, the inward turning of the eyes for near objects. Monocular c...

Depth perception is the ability to see the world in three dimensions and judge distance, even though each retina receives a flat image. The brain uses binocular cues (retinal disparity, convergence) and monocular cues (such as linear per...

Group polarization is the tendency for discussion to make a group's average attitude more extreme in the direction it already leaned. Two accounts explain it: persuasive arguments (informational influence) and social comparison (normativ...

Informational social influence is conforming because you treat other people's behavior as evidence of what is correct. It is strongest when a situation is ambiguous or you feel unsure, and it often leads to private acceptance. Normative...

Mania is a distinct period of abnormally elevated or irritable mood with increased energy and activity. A manic episode marks bipolar I disorder, whereas the milder hypomania, paired with a major depressive episode, marks bipolar II.

The orbitofrontal cortex is the lowest part of the prefrontal cortex, just above the eye sockets. It helps weigh rewards and consequences, guide decisions, and restrain impulses. Damage often produces impulsive, socially inappropriate be...

Rote rehearsal (maintenance rehearsal) is repeating information over and over without working with its meaning, which keeps it active in short-term memory. The testable point: it is shallow processing and usually gives weaker long-term m...

Self-determination theory (Deci and Ryan) says motivation and well-being depend on three innate psychological needs: autonomy, competence, and relatedness. Settings that support them tend to foster intrinsic motivation, while controlling...