Dictionary of Terms


Absolute Threshold The minimum value of a stimulus that can be detected.

Accommodation Changes in the thickness of the lens of the eye that focus images of near or distant objects on the retina. Also, the process by which existing schemata are modified or changed by new experiences.

Acquisition In classical conditioning, the time during which a CR first appears and increases in frequency.

Action Potential A brief electrochemical event that is carried by an axon from the soma of the neuron to its terminal buttons; causes the release of a transmitter substance.

Activational Effect The effect of a hormone on a physiological system that has already developed. If the effect involves the brain, it can influence behavior. An example is facilitation of sexual arousal and performance.

Actor-Observer Effect The tendency to attribute one's own behavior to situational factors but others¹ behavior to dispositional factors.

Adaptive Significance The effectiveness of behavior in aiding organisms in adjusting to changing environmental conditions.

Aerobic Exercises Physical activity that expends considerable energy, increases blood flow and respiration and thereby stimulates and strengthens the heart and lungs and increase the body's efficient use of oxygen.

Agoraphobia A mental disorder characterized by fear of and avoidance of being alone in public places; this disorder is often accompanied by panic attacks.

Agrammatism A language disturbance; difficulty in the production and comprehension of grammatical features, such as proper use of function words, word endings, and word order. Often seen in cases of Broca's aphasia.

Alcoholism An addiction to ethanol, which is the psychoactive agent in alcohol.

Algorithm A procedure that consists of a series of steps that will solve a specific type of problem.

Alleles Alternative forms of the same gene.

Alpha Activity Rhythmical, medium-frequency activity of the electroencephalogram, usually indicating a state of quiet relaxation.

Altruism The unselfish concern of one individual for the welfare of another.

Alzheimer's disease A fatal degenerative disease in which neurons of the brain progressively die, causing loss of memory and other cognitive processes.

Amygdala A part of the limbic system of the brain located deep in the temporal lobe; damage causes changes in emotional and aggressive behavior.

Anal Stage The second of Freud's psychosexual stages, during which the primary erogenous zone is the anal region. During this time, children take pleasure in retaining or expelling feces.

Anatomical Coding A means of representing information by the nervous system; different features are coded by the activity of different neurons.

Androgen Insensitivity Syndrome An inherited condition caused by a lack of functioning androgen receptors. Because androgens cannot exert their effects, a person with XY sex chromosomes develops as a female, with female external genitalia.

Androgens The primary class of sex hormones in males. The most important androgen is testosterone.

Animism The belief that all animals and all moving objects possess spirits providing their motive force.

Anorexia Nervosa An eating disorder characterized by attempts to lose weight, sometimes to the point of starvation.

Anterior/Posterior Toward the front/back.

Anterograde Amnesia A disorder caused by brain damage that disrupts a person¹s ability to form new long-term memories of events that occur after the time of the brain damage.

Antianxiety Drug A "tranquilizer," which reduces anxiety. The most common include chlordiazepoxide (Librium) and diazepam (Valium).

Antianxiety Drugs Drugs used to treat anxiety-related disorders.

Antibodies Proteins in the immune system that recognize antigens and help kill invading microorganisms.

Anticipatory Anxiety A fear of having a panic attack; may lead to the development of agoraphobia.

Antidepressant Drugs Drugs used to treat depression.

Antigen The unique proteins found on the surface of bacteria; these proteins are what enable the immune system to recognize the bacteria as foreign substances.

Antimanic Drugs Drugs used to treat bipolar disorder and mania.

Antipsychotic Drugs Drugs used to treat psychotic disorders such as schizophrenia.

Antisocial Personality Disorder A disorder characterized by a failure to conform to standards of decency; repeated lying and stealing; a failure to sustain lasting, loving relationships; low tolerance of boredom; and a complete lack of guilt.

Anxiety A sense of apprehension or doom that is accompanied by many physiological reactions, such as accelerated heart rate, sweaty palms, and tightness in the stomach.

Appeasement Gesture A stereotyped gesture made by a submissive animal in response to a threat gesture by a dominant animal; tends to inhibit an attack.

Archetypes Universal thought forms and patterns that Jung believed resided in the collective unconscious.

Artificial Intelligence A field of study in which computer programs are designed to simulate human cognitive abilities with the expectation that the endeavor will help the investigator understand the mechanisms that underlie these abilities.

Artificial Selection A procedure in which animals are deliberately mated to produce offspring that possess particularly desirable characteristics.

Assimilation The process by which new information about the world is modified to fit existing schemata.

Attachment A social and emotional bond between infant and caregiver that spans both time and space.

Attitude An evaluation of persons, places, and things.

Attribution The process by which people infer the causes of other people's behavior.

Auditory Hair Cell The sensory neuron of the auditory system; located on the basilar membrane.

Autoimmune Diseases Diseases such as rheumatoid arthritis, diabetes, lupus, and multiple sclerosis, in which the immune system attacks and destroys some of the body¹s own tissue.

Automatic Processing The formation of memories of events and experiences with little or no attention or effort.

Autonomic Nervous System (ANS) The portion of the peripheral nervous system that controls the functions of the glands and internal organs.

Availability Heuristic A general rule for decision making through which a person judges the likelihood or importance of an event by the ease with which examples of that event come to mind.

Aversion Therapy A form of treatment in which the client is trained to respond negatively to a neutral stimulus that has been paired with an aversive stimulus.

Avoidance Response An operant response acquired through negative reinforcement that prevents an aversive stimulus from occurring.

Avoidant Attachment A kind of attachment in which infants avoid or ignore their mothers and often do not cuddle when held.

Axon A long, thin part of a neuron attached to the soma; divides into a few or many branches, ending in terminal buttons.

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