1,800+ MCAT terms, defined.

Sensorimotor is Piaget's first stage of cognitive development, lasting from birth to about age 2, in which infants learn through their senses and motor actions. The most testable point is object permanence, the understanding that objects...

Sublimation is a defense mechanism in Freud's psychodynamic theory in which an unacceptable impulse, such as aggression or sexual desire, is redirected into a socially acceptable activity. It is usually classed as a mature, adaptive defe...

The visual pathway carries signals from the retina via the optic nerve, optic chiasm, and thalamus (LGN) to the primary visual cortex in the occipital lobe. Testable point: nasal retinal fibers cross at the chiasm, so each visual field i...

Feature detection is the idea that specific neurons in the visual cortex respond to particular stimulus features, such as edges, orientation, or motion, and later areas combine these into whole objects. It is a bottom-up process, and the...

The sensorimotor stage is the first stage in Piaget's theory of cognitive development, lasting from birth to about age 2. Infants learn by acting on the world with their senses and movements. Its key milestone is object permanence, knowi...

Incentive theory says behavior is motivated by external rewards or the avoidance of punishments that pull a person toward a goal, rather than by an internal need pushing. The testable contrast is with drive-reduction theory, though many...

Nicotine is a stimulant in tobacco that binds nicotinic acetylcholine receptors, raising dopamine in the brain's reward pathway. The MCAT uses it as a model of addiction: reinforcement, tolerance, and withdrawal keep use going.

Jean Piaget proposed a stage theory of cognitive development in which children build schemas through assimilation and accommodation. The stages occur in a fixed order: sensorimotor, preoperational, concrete operational, formal operationa...

Self-identities are the specific roles, traits, and group memberships (such as student, daughter, athlete, or a gender, racial, or religious group) that a person uses to define themselves. Each is one part of the self-concept, and the MC...

Wernicke's area is a region of the posterior temporal lobe, in the left hemisphere for most people, that supports language comprehension. Damage causes Wernicke's aphasia: fluent but meaningless speech with poor comprehension, unlike Bro...

An expectation is a belief about how a person will act or how an event will turn out, drawn from schemas, experience, or norms. It shapes perception and behavior, so in a self-fulfilling prophecy the belief leads to actions that help mak...

Linguistic determinism is the strong form of the Sapir-Whorf hypothesis: the language a person speaks determines, or limits, what they can think. The weaker form, linguistic relativity, says language only influences thought, and most evi...

Broca's aphasia is a language disorder from damage to Broca's area, in the left frontal lobe in most people. It causes slow, effortful, nonfluent speech with relatively preserved comprehension. Key contrast: Wernicke's aphasia gives flue...

Projection bias is the tendency to assume that other people, or our own future selves, share our current thoughts, feelings, and preferences. Testable point: it is a cognitive bias about assumed similarity, not Freud's projection defense...

Sleep spindles are brief bursts of fast, rhythmic EEG activity (roughly 12–14 Hz) seen in stage 2 non-REM sleep, usually alongside K-complexes. The most testable point: spindles and K-complexes are the EEG signature that marks stage 2 sl...

The Yerkes-Dodson law says performance is best at a moderate level of arousal and drops when arousal is too low or too high, giving an inverted U. The best level depends on the task: easy or well-practiced tasks peak at higher arousal, d...

The fovea is a small pit at the center of the retina that is densely packed with cones and has essentially no rods. It gives the sharpest, most color-sensitive vision in bright light, so acuity and color fall off in the periphery, where...

The medulla oblongata is the lowest part of the brainstem, in the hindbrain, just above the spinal cord. It controls automatic, life-sustaining functions such as breathing, heart rate, blood pressure, and reflexes like swallowing and vom...

Mirror neurons are neurons that fire both when an individual performs an action and when that individual watches another perform a similar action. They are proposed to support observational learning, imitation, and empathy, though their...

The otolithic organs, the utricle and saccule in the inner ear's vestibule, sense linear acceleration and head position relative to gravity. The usual MCAT contrast is that the semicircular canals sense rotation instead.

Hypnosis is a technique in which a guide uses relaxation, focused attention, and suggestions to produce heightened suggestibility. Whether it is a distinct altered state of consciousness (state view) or the result of expectation and role...

A neutral stimulus is one that does not trigger the response of interest before learning. In classical conditioning it is paired with an unconditioned stimulus and becomes a conditioned stimulus. It is the same stimulus before and after,...

Personality disorders are enduring, inflexible patterns of thinking, emotion, and behavior that deviate from cultural expectations and cause distress or impairment. The most testable point is the three DSM clusters: A (odd, eccentric), B...

Repression is a Freudian defense mechanism in which the ego pushes anxiety-provoking thoughts, memories, or urges out of conscious awareness into the unconscious. It is unconscious and involuntary, which separates it from suppression, wh...

Linguistic relativity (the Sapir-Whorf hypothesis) is the idea that the language a person speaks shapes how they perceive and think. The strong form, linguistic determinism, says language determines thought; the weak form, which has more...

Spreading activation is a model of semantic memory in which activating one concept in a network of linked nodes excites related nodes, making them easier to retrieve. It explains priming: related words are recognized faster after a prime.

Short-term memory is the temporary store in the Atkinson-Shiffrin model, holding about 7 ± 2 items for roughly 20–30 seconds unless rehearsed. Chunking raises how much information fits; newer accounts treat the active version as working...

Humanistic theory is a personality perspective that stresses free will, innate goodness, and a drive toward self-actualization. The testable point: Rogers links a gap between real self and ideal self (incongruence) to distress, and uncon...

In Freud's psychoanalytic theory, the superego is the part of personality that holds internalized moral standards and ideals, learned from parents and society. It opposes the id's urges and pushes behavior toward what is morally right, n...

A fixed-action pattern is an innate, stereotyped sequence of behavior set off by a specific cue (a sign stimulus) and usually carried through to completion once begun. It is species-typical and unlearned, so the MCAT contrasts it with le...

The mere exposure effect is the tendency to like a stimulus more after repeated contact with it, even without reward or awareness of the earlier exposures. It underlies familiarity-based attraction (proximity) and tends to hold for neutr...

The forebrain is the most anterior of the three embryonic brain divisions (forebrain, midbrain, hindbrain). It includes the cerebral cortex, thalamus, hypothalamus, and limbic structures such as the amygdala and hippocampus. The MCAT tes...

Optimal arousal is the moderate level of physiological and mental activation at which performance tends to be best, as described by arousal theory and the Yerkes-Dodson law. Performance forms an inverted U with arousal, and the peak is l...

Regression is a Freudian defense mechanism in which a person under stress or anxiety reverts to behavior typical of an earlier, less mature developmental stage, such as an adult throwing a tantrum. The exam tests spotting it in a vignett...

The Hawthorne effect is a change in participants' behavior caused by knowing they are being observed or given attention, rather than by the variable the researcher manipulated. It threatens a study's validity, and a control group that ge...

Learned helplessness is a passive, resigned state that develops after repeated exposure to unavoidable aversive events, so an individual stops trying to escape even when escape later becomes possible. The most testable point is that the...

The dependent variable is the outcome a researcher measures to see whether it changes in response to the independent variable. In an experiment, a difference in it between groups is the effect being tested. To spot it, ask what was measu...

Knowledge is information stored in long-term memory and organized into schemas. It is divided into declarative (explicit) knowledge of facts and events and procedural (implicit) knowledge of skills. Hippocampal damage can impair new decl...

The olfactory epithelium is the patch of tissue in the upper nasal cavity that holds olfactory receptor neurons, which are chemoreceptors that bind odorant molecules. Unlike vision, hearing, and touch, its signals reach the cortex and li...

The prefrontal cortex is the front part of the frontal lobe. It supports executive functions such as planning, decision making, judgment, and impulse control, partly by regulating limbic emotional responses. Damage (Phineas Gage) typical...

Alarm is the first stage of Selye's general adaptation syndrome, when a stressor triggers the sympathetic fight-or-flight response. The testable point is the order of the stages: alarm, then resistance, then exhaustion.

External validity is the extent to which a study's findings generalize beyond its own sample, setting, and conditions to other people, places, and times. The most testable point: an unrepresentative sample or an artificial lab setting lo...

Distinctiveness is whether a person acts this way only in this particular situation or across many situations. It is one cue in Kelley's covariation model of attribution. High distinctiveness points to a situational (external) cause; low...

The just world hypothesis (Melvin Lerner) is the belief that the world is fair, so people get what they deserve. Most testable point: it often leads observers to blame victims, attributing misfortune to the person's character or choices...

Moral development is how a person's reasoning about right and wrong changes over time. In Kohlberg's theory it moves through three levels, preconventional, conventional and postconventional, and the stage is set by the reasoning given, n...

Sensory processing is how the nervous system detects a stimulus, transduces it into neural signals, and sends them to the brain, where they are interpreted as perception. Most testable: bottom-up processing is stimulus-driven, while top-...

Denial is an ego defense mechanism in psychoanalytic theory in which a person refuses to accept a real, threatening fact and acts as though it is not true. The most testable point: denial rejects external reality, whereas repression push...

Internal validity is how confidently a study shows that the independent variable, rather than some other factor, caused the change in the dependent variable. Random assignment, control groups and control of confounds raise it, and tight...

Motor function is the nervous system's control of movement: the primary motor cortex (precentral gyrus, frontal lobe) sends commands down the spinal cord to skeletal muscle. Testable point: each hemisphere mainly controls the opposite si...

The serial position effect is the tendency to recall items at the start (primacy) and end (recency) of a list better than items in the middle. Primacy reflects rehearsal and long-term storage; recency reflects short-term memory. A distra...