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abnormal psychology See psychopathology.
above-average effect A data pattern, commonly observed in individualist cultures, in which people rate themselves as being above average on many dimensions, for example, a better driver than the average, more likeable than the average, and so on.
accommodation (1) The process by which the lens is thickened or flattened to focus on an object. (2) In Piaget's theory of development, one of the twin processes that underlies cognitive development. Accommodation is the way the child changes his schemas as he continues to interact with the environment. See assimilation.
acetylcholine (Ach) A neurotransmitter found in many parts of the nervous system. Among many other functions, it serves as an excitatory transmitter at the synaptic junctions between muscle fibers and motor neurons.
ACh See acetylcholine.
achromatic colors Colors, such as black, white, and the neutral grays, that do not have the property of hue.
acquisition The initial step toward remembering in which new information is taken in.
action potential A brief change in the electrical potential of an axon, which is the physical basis of the nervous impulse.
activation-synthesis hypothesis An account which holds that dreams may reflect the brain's aroused state during REM sleep, when the cerebral cortex is active but shut off from sensory input. This helps explain the content and often disjointed form of REM dreams.
active-span tasks Tasks in which research participants are asked to remember materials while simultaneously working on some other task; such tasks are an effective means of measuring working memory's capacity.
activity dependence A property of neuronal plasticity such that changes in a neuron's functioning will occur only if that neuron is active (i.e., firing) at the same time as another neuron.
actor-observer difference The difference in attributions made by actors who describe their own actions and observers who describe another person's. The former emphasizes external, situational causes; the latter, internal, dispositional factors. See also fundamental attribution error.
act-outcome representation A type of association hypothesized by Edward Tolman to be the product of instrumental learning; an organism that has acquired this sort of association has acquired the knowledge that a certain type of act leads to a particular outcome.
acuity The ability to distinguish between separate points projected on the retina. Acuity is greatest in the fovea, where the receptors are closely bunched together.
acute stress disorder A reaction sometimes observed in individuals who have experienced a traumatic event, characterized by recurrent nightmares and waking flashbacks of the traumatic event.
adaptation The process by which the sensitivity to a stimulus declines if the stimulus is continually presented.
addiction The result of repeated use of some drugs. The consequences are increased tolerance and also withdrawal symptoms if the drug is unavailable, usually causing the addiction to be self-perpetuating.
adipose cells The cells within the body that provide long-term storage of energy resources, usually in the form of fatty acids that can be converted to glucose when needed.
afferent nerves Nerves that carry messages to the brain.
agency A term referring to the view that a person has about the origins of her behaviors. People in individualist cultures often have a sense of agency in which the person herself is regarded as the source of the actions; people in collectivist cultures have a sense of agency that emphasizes the role of the situation.
aggression Hostile action directed against another member of one's species, usually intended to do physical or social harm or, for hostile intent, to limit the target's actions. Aggression must be distinguished from the behaviors involved in predation.
agnosia A disturbance in the organization of sensory information produced by lesions in certain cortical areas. An example is visual agnosia in which the patient can see but often does not recognize what he sees.
agonists Drugs that enhance the activity of a neurotransmitter, often by increasing the amount of transmitter substance available (e.g., by blocking reuptake or by increasing the availability of precursors).
agoraphobia The fear of being alone and outside of the home, especially in a public place; often observed in those with panic disorder. See also phobia.
algorithm In problem solving, a procedure in which all of the steps toward the solution are specified. See also heuristics.
all-or-none law A law that describes the fact that all action potentials have the same amplitude regardless of the stimulus that triggered them.
alpha rhythm A pattern of regular pulses, between eight and twelve per second, visible in the EEG waves of a person who is relaxed but awake, and typically with eyes closed.
Alzheimer's disease A degenerative brain disorder characterized by memory loss followed by increasing disorientation and culminating in total physical and mental helplessness. One of the major sites of the destruction is a pathway of acetylcholine-releasing cells leading from the base of the forebrain to the cortex and hippocampus. See also acetylcholine.
American Sign Language (ASL) The manual-visual language system of deaf persons in America.
amino acid The building blocks of proteins.
amplitude The height of a wave crest, used as a measure of intensity of a sound or light wave.
amygdala An almond-shaped structure in the temporal lobe that plays a central role in emotion and in the evaluation of stimuli.
amyloid plaques Large blobs of amyloid protein created in the development of Alzheimer's disease; these plaques seem to trigger an immune response in the brain, resulting in the death of many neurons.
amyloid protein A protein normally created by neurons; abnormal forms contribute to the development of Alzheimer's disease.
anal character An adult personality pattern allegedly produced (according to psychoanalysts) by a fixation on the anal stage. This character includes traits like orderliness and stinginess.
analgesic A pain reliever.
analogical representation A representation that shares some of the physical characteristics of an object; for example, a picture of a mouse is an analogical representation because it looks like the small rodent it represents.
anal stage In psychoanalytic theory, the stage of psychosexual development during which the focus of pleasure is on activities related to elimination.
analytic intelligence According to some investigators, the type of intelligence typically measured by intelligence tests and crucial for success in academic pursuits.
androgen Any male sex hormone (e.g., testosterone).
anecdotal evidence Evidence (usually just a few cases) collected informally, as in anecdotes told from one person to another.
anomia A difficulty in finding words that is often experienced by people with brain injuries.
anorexia nervosa An eating disorder that primarily afflicts young women and that is characterized by an exaggerated concern with being overweight and by compulsive dieting, sometimes to the point of self-starvation and death. See also bulimia.
A-not-B effect The tendency of infants around nine months of age to search for a hidden object by reaching for place A, where it was previously hidden, rather than a new place B, where it was hidden most recently while the child was watching.
ANS See autonomic nervous system.
antagonists Drugs that impede the activity of a neurotransmitter, often by decreasing the amount available (e.g., by speeding reuptake and decreasing availability of precursors).
anterograde amnesia A memory deficit suffered after some brain damage. It is an inability to learn and remember any information encountered after the injury, with little effect on memory for information acquired before the injury. See also retrograde amnesia.
antimanics Drugs that alleviate the symptoms of mania, the energetic phase of bipolar disorder.
antisocial personality disorder Also called psychopathy or sociopathy. The term describes persons who get into continual trouble with society, are indifferent to others, are impulsive, and have little concern for the future or remorse about the past.
anxiety A global apprehensiveness related to uncertainty.
anxiety disorders See acute stress disorder, dissociative disorders, generalized anxiety disorder, obsessive-compulsive disorder, panic disorder, phobia, post-traumatic stress disorder (PTSD), social phobia.
anxiety hierarchy See systematic desensitization.
anxiolytics Drugs that alleviate the symptoms of anxiety.
aphasia A disorder of language produced by lesions in certain areas of the cortex. A lesion in Broca's area leads to nonfluent aphasia, one in Wernicke's area to fluent aphasia.
apparent movement The perception of movement produced by stimuli that are stationary but flash on and off at appropriate positions and at appropriate time intervals.
apraxia A serious disturbance in the organization of voluntary action produced by lesions in certain cortical areas, often in the frontal lobes.
archetypes According to Carl Jung, the stories and images that constitute our collective unconscious.
arousal Activation in any of the body's systems (e.g., activation of the sympathetic nervous system or the cerebral cortex). Arousal as a general term has resisted definition, because sometimes one system is activated while another is not.
ASL See American Sign Language.
ASQ See attributional-style questionnaire.
assimilation In Piaget's theory, one of the twin processes by means of which cognitive development proceeds. Assimilation is the process whereby the environment is interpreted in terms of the schemas the child has at the time. See accomodation.
association A linkage between two psychological processes or representations as a result of past experience in which the two have occurred together.
associative links Connections in memory that tie one memory, or one concept, to another.
associative retrieval A type of memory retrieval that seems swift and effortless: the sought-after information simply "pops" into mind.
attitude A fairly stable, evaluative disposition that makes a person think, feel, or behave positively or negatively about some person, group, or social issue.
attributional-style questionnaire (ASQ) A questionnaire designed to assess a person's habitual pattern of attributing events in a certain way (e.g., to internal forces or external ones, to forces that influence just that event or to broader forces).
attribution-of-arousal theory An approach that combines the James-Lange emphasis on bodily feedback with a cognitive approach to emotion. Various stimuli can trigger a general state of arousal, which is then interpreted in light of the subject's present situation and shaped into a specific emotional experience.
atypical antidepressants A recently developed group of medications that work in varied ways on serotonin, norepinephrine, and dopamine systems to combat the symptoms of depression.
atypical antipsychotics Drugs (such as Clozaril, Risperdal, and Zyprexa) that operate by blocking receptors for both dopamine and serotonin; these drugs seem to be effective in treating schizophrenic patients' positive symptoms, such as thought disorders and hallucinations, as well as their negative symptoms, such as apathy and emotional blunting.
auditory canal The tube that carries sound from the outer ear to the eardrum.
auditory ossicles The three bones of the middle ear that transmit vibrations from the eardrum to the oval window.
authoritarian personality A cluster of personal attributes (e.g., submission to persons above and harshness to those below) and social attitudes (e.g., prejudice against minority groups) that is sometimes held to constitute a distinct personality.
authoritative-reciprocal pattern A pattern of child rearing in which parents exercise considerable power but also respond to the child's point of view and reasonable demands. Parents following this pattern set rules of conduct and are fairly demanding but also encourage the child's independence and self-expression.
autocratic pattern A pattern of child rearing in which the parents control the child strictly, setting stern and usually unexplained rules whose infraction leads to severe, often physical, punishment.
automaticity The state that is achieved when an action has gone through the process of automatization.
autonomic division See autonomic nervous system.
autonomic nervous system (ANS) A part of the nervous system that controls the internal organs, usually not under voluntary control.
availability heuristic A rule of thumb often used to make probability estimates, which depends on the frequency with which certain events readily come to mind. This can lead to errors, since, for example, very vivid events will be remembered out of proportion to their actual frequency of occurrence.
aversion therapy A form of behavior therapy in which the undesirable response leads to an aversive stimulus (e.g., the patient shocks herself every time she reaches for a cigarette).
avoidance responses Responses that allow an organism to avoid contact with an aversive stimulus.
axon Part of a neuron that transmits impulses to other neurons or effectors.
axonal branches A structure in many neurons in which the axon forks into several branches, with the neuronal impulse propagated to all branches.
axon terminals The knoblike swellings on the ends of an axon. The terminals contain the synaptic vesicles that are filled with neurotransmitters.
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