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tachycardia: A racing of the heart, often associated with high levels of anxiety.

tardive dyskinesia: A muscular disturbance of older patients who have taken phenothiazines for a very long time, marked by involuntary lip smacking and chin wagging.

Taylor Manifest Anxiety Scale: Fifty items drawn from the MMPI, used as a self-report questionnaire to assess anxiety.

temporal lobe: A large area of each cerebral hemisphere situated below the lateral sulcus and in front of the occipital lobe; contains primary auditory projection and association areas and general association areas.

tertiary prevention: See prevention.

testes: Male reproductive glands or gonads; the site where sperm develop and are stored.

testosterone: Male sex hormone secreted by the testes that is responsible for the development of sex characteristics, such as enlargement of the testes and growth of facial hair.

test-retest reliability: See reliability.

tetrahydrocannabinol (THC): The major active chemical in marijuana and hashish.

T-group: See sensitivity training group.

thalamus: A major brain relay station consisting of two egg-shaped lobes located in the diencephalon; it receives impulses from all sensory areas except the olfactory and transmits them to the cerebrum.

Thanatos: In psychoanalytic theory, the death instinct; with Eros, the two basic instincts within the id.

Thematic Apperception Test (TAT): A projective test consisting of a set of black-and-white pictures reproduced on cards, each depicting a potentially emotion-laden situation. The examinee, presented with the cards one at a time, is instructed to make up a story about each situation.

theory: A formally stated and coherent set of propositions that purport to explain a range of phenomena, order them in a logical way, and suggest what additional information might be gleaned under certain conditions.

therapeutic community: A concept in mental health care that views the total environment as contributing to prevention or treatment.

thiamine: One of the complex of B vitamins.

third-variable problem: The difficulty in the correlational method of research whereby the relationship between two variables may be attributable to a third factor.

Thorazine: Trade name for chlorpromazine, one of the antipsychotic drugs and a member of the phenothiazine group.

thought disorder: A symptom of schizophrenia, evidenced by problems such as incoherence, loose associations, poverty of speech, and poverty of content of speech.

thought listing: A cognitive assessment technique that involves a person writing down his or her thoughts upon experiencing an event, such as taking a test or meeting a person.

thyroid gland: An endocrine structure whose two lobes are located on either side of the windpipe; it secretes thyroxin.

time-of-measurement effects: A possible confound in longitudinal studies whereby conditions at a particular point in time can have a specific effect on a variable that is being studied over time.

time-out: An operant conditioning punishment procedure in which, after bad behaviour, the person is temporarily removed from a setting where reinforcers can be obtained and placed in a less desirable setting, for example, in a boring room.

token economy: A behaviour therapy procedure, based on operant conditioning principles, in which institutionalized patients are given scrip rewards, such as poker chips, for socially constructive behaviour. The tokens can be exchanged for desirable items and activities such as cigarettes and extra time away from the ward.

tolerance: A physiological process in which greater and greater amounts of an addictive drug are required to produce the same effect. See substance dependence.

trait: A somatic characteristic or an enduring psychological predisposition to respond in a particular way, distinguishing one individual from another.

tranquilizer: A drug that reduces anxiety and agitation, such as Valium. See anxiolytics.

transference: The venting of the patientís emotions, either positive or negative, by treating the psychoanalyst as the symbolic representative of someone important in the past. An example is the patientís becoming angry with the psychoanalyst to release emotions actually felt toward his or her father.

transference neurosis: A crucial phase of psychoanalysis during which the patient reacts emotionally toward the psychoanalyst, treating the analyst as a parent and reliving childhood experiences in his or her presence. It enables both psychoanalyst and patient to examine hitherto repressed conflicts in the light of present-day reality.

transsexual: A person who believes he or she is opposite in sex to his or her biological endowment; sex-reassignment surgery is frequently desired.

transvestic fetishism: The practice of dressing in the clothing of the opposite sex, for the purpose of sexual arousal.

trauma: A severe physical injury or wound to the body caused by an external force, or a psychological shock having a lasting effect on mental life.

traumatic disease: An illness produced by external assault, such as poison, a blow, or stress; for example, a broken leg.

tremor: An involuntary quivering of voluntary muscle, usually limited to small musculature of particular areas.

trepanning: The act of making a surgical opening in a living skull. This act was sometimes performed because of the belief that it would allow evil spirits to leave the body.

triadic reciprocality: The influence of cognition and behaviour on each other through the relationships among thinking, behaviour, and the environment.

tricyclic drugs: A group of antidepressants with molecular structures characterized by three fused rings. Tricyclics are known to interfere with the reuptake of norepinephrine and serotonin by a neuron after it has fired.

trisomy: A condition wherein there are three rather than the usual pair of homologous chromosomes within the cell nucleus.

tumescence: The flow of blood into the genitals.

tumour (neoplasm): Abnormal growth that when located in the brain can either be malignant and directly destroy brain tissue or be benign and disrupt functioning by increasing intra-cranial pressure.

twin method: Research strategy in behaviour genetics in which concordance rates of monozygotic and dizygotic twins are compared.

two-factor theory: Mowrerís theory of avoidance learning according to which (1) fear is attached to a neutral stimulus by pairing it with a noxious unconditioned stimulus, and (2) a person learns to escape the fear elicited by the conditioned stimulus, thereby avoiding the unconditioned stimulus. See fear-drive.

Type A behaviour pattern: One of two contrasting psychological patterns revealed through studies seeking the cause of coronary heart disease. Type A people are competitive, rushed, hostile, and over-committed to their work, and are believed to be at heightened risk for heart disease. Those who meet the other pattern, Type B people, are more relaxed and relatively free of pressure.