1,800+ MCAT terms, defined.

Social loafing is the tendency for individuals to put in less effort on a task when working in a group than when working alone. It is most likely when individual contributions cannot be identified or evaluated, and it tends to shrink whe...

In Piaget's theory, assimilation is fitting new information into an existing schema without changing that schema. The key contrast is accommodation, where the schema itself is modified. In sociology, assimilation means a minority group a...

Problem solving is the cognitive process of finding a way to reach a goal when the route is not obvious. The most testable point is algorithm versus heuristic: an algorithm is a step-by-step procedure that gives the correct answer if fol...

A category is a mental grouping of objects, people, or events judged to share features, so new items can be classified and their properties inferred. The MCAT tests how categories are represented: by a prototype (the best or average exam...

Freud's psychosexual stages are five phases of development (oral, anal, phallic, latency, genital) in which libido centers on a different body zone. Unresolved conflict at a stage, from frustration or overindulgence, can cause a fixation...

Pheromones are chemical signals released by one individual that influence the behavior or physiology of another member of the same species. They are detected by smell, and in many animals by the vomeronasal organ. Whether humans respond...

Obedience is changing behavior because an authority figure gives a direct command. In Milgram's shock experiments, most participants in the baseline version went to the maximum voltage, and obedience tended to fall when the authority was...

Actor-observer bias is the tendency to explain our own behavior with situational (external) causes but to explain other people's behavior with dispositional (internal) causes. It is an attribution bias, so the testable contrast is self →...

Divided attention is attending to more than one stimulus or task at the same time. Because attentional capacity is limited, performance on one or both tasks usually declines, especially when the tasks are novel, effortful, or compete for...

Locus of control is a person's belief about what determines outcomes in their life. An internal locus attributes outcomes to one's own actions; an external locus attributes them to luck, fate, or other people. An internal locus tends to...

The halo effect is a social perception bias in which one positive trait, such as attractiveness, shapes overall judgments of a person and leads us to assume other good traits. The most testable point is that a single impression spreads t...

The cortex is the folded outer layer of the cerebrum, where much higher-order processing happens: perception, language, planning, and voluntary movement. Most testable: link each lobe to its main function, such as occipital for vision an...

In operant conditioning, reinforcement is a consequence that makes the preceding behavior more likely to recur. Positive reinforcement adds a stimulus and negative reinforcement removes an aversive one; both increase behavior, whereas pu...

Zimbardo's 1971 study randomly assigned college students to be guards or prisoners in a mock prison; the guards became harsh and the study ended early. The MCAT uses it to show how situations and assigned social roles can strongly shape...

Gestalt principles are rules describing how the visual system groups separate elements into organized wholes. They include proximity, similarity, continuity, closure, symmetry, common fate and figure-ground. The testable point is that th...

The humanistic perspective holds that people have free will and an inherent drive toward growth and self-actualization. Its key ideas are Maslow's hierarchy of needs and Rogers's unconditional positive regard, which helps the real self m...

The psychoanalytic perspective, from Freud, explains personality and behavior as shaped by unconscious drives and conflicts, many rooted in early childhood. The most testable points are the id–ego–superego conflict and the defense mechan...

Stereotype threat is the concern a person feels about confirming a negative stereotype of their group, which can impair performance on a task tied to that stereotype. It is a situational effect, not a measure of true ability, and it tend...

Projection is a psychoanalytic (Freudian) defense mechanism in which a person attributes their own unacceptable thoughts, feelings or impulses to someone else, reducing anxiety. Testable point: the feeling is assigned to the other person...

Photoreceptors are the rods and cones, retinal cells that transduce light into neural signals. Rods work in dim light and give no color information; cones need brighter light and give color and sharp detail, and are concentrated in the f...

A stressor is an event, condition or demand that triggers the stress response. Stress is the reaction, not the stimulus. Whether an event acts as a stressor depends largely on appraisal, so the same event can be a threat for one person a...

Attribution theory is the social psychology account of how people explain behavior, as dispositional (internal traits) or situational (external circumstances). Most testable: observers often favor dispositional explanations for others (f...

Cognitive behavioral therapy (CBT) is a structured psychotherapy that treats problems such as depression and anxiety by identifying and changing maladaptive thoughts and behaviors. Its key idea is that thoughts influence emotions and act...

Distress is the negative form of stress: the response to a demand that a person appraises as threatening or beyond their coping resources. It contrasts with eustress, the positive, motivating kind. The testable point is that appraisal, n...

Korsakoff's syndrome is a memory disorder caused by thiamine (vitamin B1) deficiency, most often seen with chronic alcohol use. It produces severe anterograde amnesia, often with some retrograde amnesia and confabulation. Implicit memory...

Priming is when exposure to one stimulus (the prime) changes how a later stimulus is processed, usually without awareness. It is a form of implicit memory, explained by spreading activation in a semantic network. Most testable: a related...

Dishabituation is the recovery of a response that had declined through habituation, usually after a new or different stimulus is presented. In infant studies, renewed looking time after a change suggests the baby can tell the new stimulu...

Spatial refers to location, distance, direction, and arrangement. In psychology it covers perceiving and remembering where things are: the dorsal "where" visual stream (parietal lobe) and hippocampal spatial memory. In sociology, spatial...

Alzheimer's disease is a progressive neurodegenerative disorder and a leading cause of dementia, marked by gradual memory loss and cognitive decline. It is linked to beta-amyloid plaques and tau tangles, with early hippocampal damage, so...

Cognition is the set of mental processes used to acquire, store, and use information, including attention, memory, language, reasoning, and problem solving. The MCAT most often tests it through Piaget's stages of cognitive development an...

Sensory adaptation is the decrease in sensitivity of sensory receptors (and the neural response) to a constant, unchanging stimulus over time. It lets you notice changes rather than steady background. Responses to a stimulus that changes...

A belief is the acceptance that a claim is true, whether or not the evidence is solid. Beliefs form the cognitive component of an attitude. The testable point is that beliefs can persist after their supporting evidence is discredited (be...

In Freud's psychodynamic theory, defense mechanisms are unconscious strategies the ego uses to reduce anxiety from conflict among the id, superego and reality. The MCAT usually gives a short vignette and asks you to name the mechanism, s...

A reflex is an automatic, involuntary response to a specific stimulus, often routed through a simple spinal circuit without input from the brain. The most testable point: infant reflexes (rooting, sucking, grasp, Moro, Babinski) are pres...

Conscious means aware of yourself and your surroundings, including current thoughts, sensations and perceptions. The MCAT treats consciousness as a range of states (alert, drowsy, asleep, hypnotized, drug-altered). In Freud's model, the...

A hallucinogen is a psychoactive drug that alters perception, mood and thought, often producing hallucinations. On the MCAT, LSD, psilocybin and mescaline are the standard examples, and LSD and psilocybin act largely on serotonin receptors.

In Freud's psychoanalytic theory, libido is the psychic energy of the life (sexual, pleasure-seeking) instincts, which arises in the id. The most testable point is that libido is invested in different body areas across the psychosexual s...

Mood is a sustained, relatively low-intensity emotional state that is often diffuse and not tied to one specific trigger. The testable contrast is with emotion, which is typically briefer, more intense, and directed at a particular stimu...

Bottom-up processing is perception that starts with the raw sensory input (features such as edges, color and motion) and builds up to a recognized whole. It is data-driven, unlike top-down processing, which uses expectations and context....

Self-actualization is the drive to realize one's full potential, the top level of Maslow's hierarchy of needs. In Maslow's model it generally becomes the main motivator only after lower needs are reasonably met; Rogers also used the rela...

The bystander effect is the tendency for a person to be less likely to help someone in need when other people are present. It is explained by diffusion of responsibility and by reading others' inaction as a sign nothing is wrong (plurali...

In Freud's psychosexual theory, the phallic stage (about ages 3 to 6) is when the child's libido centers on the genitals. The Oedipus complex (and, in Freud's account, the Electra complex) arises here, and its resolution through identifi...

The reticular formation is a network of neurons running through the brainstem (core of the medulla, pons and midbrain) that regulates arousal, alertness and the sleep-wake cycle. Its ascending activating role is the most testable point:...

In Freud's psychoanalytic theory, the unconscious is the level of mind holding wishes, urges and memories outside awareness, often because they are threatening. The testable point: it is said to shape behavior indirectly, through dreams,...

Recognition is a memory retrieval task in which you identify information as previously encountered when it is presented to you, as in multiple choice or a police lineup. It is usually easier than recall, which requires you to produce the...

Anger is a basic emotion, usually a high-arousal, negative response to a perceived threat, insult or blocked goal. It has physiological, cognitive and behavioral components. The exam often tests that its facial expression is recognized a...

REM is rapid eye movement sleep, the stage where the EEG looks nearly awake (fast, low-amplitude waves), dreams are most vivid, and skeletal muscles are essentially paralyzed. That mix is why it is called paradoxical sleep. Dreams also o...

Weber's law says the just noticeable difference (JND) between two stimuli is a constant proportion of the original stimulus intensity, not a fixed amount. The stronger the starting stimulus, the larger the change needed to notice it. It...

Bandura's social learning theory says people learn behaviors by observing models and the consequences the models receive, not only through their own reinforcement or punishment. Most testable: in the Bobo doll study, children imitated an...

Ivan Pavlov was the Russian physiologist who discovered classical conditioning, in which a neutral stimulus repeatedly paired with an unconditioned stimulus comes to trigger a conditioned response. The most testable skill is labeling the...