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id: In psychoanalytic theory, that part of the personality present at birth, composed of all the energy of the psyche, and expressed as biological urges that strive continually for gratification.

ideas of reference: Delusional thinking that reads personal significance into seemingly trivial remarks and activities of others and completely unrelated events.

identity crisis: A developmental period in adolescence marked by concerns about who one is and what one is going to do with his or her life.

idiographic: In psychology, relating to investigative procedures that consider the unique characteristics of a single person, studying them in depth, as in the case study. Contrast with nomothetic.

idiot savant: An individual with a rare form of mental retardation, extraordinarily talented in one or a few limited areas of intellectual achievement; sometimes called autistic savant.

illusion: A misperception of a real external stimulus, such as hearing the slapping of waves as footsteps.

imipramine: An antidepressant drug, one of the tricyclic group, trade name Tofranil.

in absentia: Literally, "in oneís absence." Courts are concerned that a person be able to participate personally and meaningfully in his or her own trial and not be tried in absentia because of a distracting mental disorder.

in vivo: As applied in psychology, taking place in a real-life situation.

in vivo exposure: The process of having a phobic individual encounter or experience the subject of their phobia in a real-life situation.

inappropriate affect: Emotional responses that are out of context, such as laughter when hearing sad news.

incest: Sexual relations between close relatives, most often between daughter and father or between brother and sister.

incidence: In epidemiological studies of a particular disorder, the rate at which new cases occur in a given place at a given time. Compare with prevalence.

incoherence: In schizophrenia, an aspect of thought disorder wherein verbal expression is marked by disconnectedness, fragmented thoughts, and jumbled phrases.

independent variable: In a psychological experiment, the factor, experience, or treatment that is under the control of the experimenter and that is expected to have an effect on participants as assessed by changes in the dependent variable.

index case (proband): The person who in a genetic investigation bears the diagnosis or trait in which the investigator is interested.

individual psychology: A variation of Freudís psychoanalysis introduced by Alfred Adler and focusing less on biological drives and more on such factors as peopleís conscious beliefs and goals for self-betterment.

infectious disease: An illness caused when a microorganism, such as a bacterium or a virus, invades the body, multiplies, and attacks a specific organ or organ system; pneumonia is an example.

informed consent: The agreement of a person to serve as a research participant or to enter therapy after being told the possible outcomes, both benefits and risks.

inhibited male orgasm: A recurrent and persistent delay or absence of ejaculation after an adequate phase of sexual excitement.

insanity defence: The legal argument that a defendant should not be held ascriptively responsible for an illegal act if the conduct is attributable to mental illness.

insight therapy: A general term for any psychotherapy that assumes that people become disordered because they do not adequately understand what motivates them, especially when their needs and drives conflict.

instrumental learning: See operant conditioning.

instrumental support: The provision of tangible assistance (e.g., meal preparation) to people in need.

intelligence quotient (IQ): A standardized measure indicating how far an individualís raw score on an intelligence test is from the average raw score of his or her chronological age group.

intelligence test: A standardized means of assessing a personís current mental ability, for example, the StanfordĖBinet test and the Wechsler Adult Intelligence Scale.

interactionism: The notion that behaviour is a joint function of personal characteristics and the properties of the situations that are experienced.

internal consistency reliability: See reliability.

internal validity: See validity.

interpersonal therapy: A psychodynamic psychotherapy that focuses on the patientís interactions with others and that directly teaches how better to relate to others.

interpretation: In psychoanalysis, a key procedure in which the psychoanalyst points out to the patient where resistance exists and what certain dreams and verbalizations reveal about impulses repressed in the unconscious; more generally, any statement by a therapist that construes the clientís problem in a new way.

interrater reliability: See reliability.

introjection: In psychoanalytic theory, the unconscious incorporation of the values, attitudes, and qualities of another person into the individualís own ego structure.

introspection: A procedure whereby trained subjects are asked to report on their conscious experiences. This was the principal method of study in early twentieth-century psychology.

irrational beliefs: Self-defeating assumptions that are assumed by rational-emotive therapists to underlie psychological distress.

irresistible impulse: The term used in an 1834 Ohio court ruling on criminal responsibility that determined that an insanity defence can be established by proving that the accused had an uncontrollable urge to perform the act.