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object choice: In the psychology of sex, the type of person or thing selected as a focus for sexual desire or activity.


objective (realistic) anxiety: In psychoanalytic theory, the ego’s reaction to danger in the external world; realistic fear. Contrast with neurotic anxiety.


observer drift: The tendency of two raters of behaviour to begin to agree with each other, achieving unusually high levels of reliability; their way of coding behaviour differentiates their scores from those of another pair of raters. This is regarded as a threat to reliable and valid behavioural assessment.


obsession: An intrusive and recurring thought that seems irrational and uncontrollable to the person experiencing it.


obsessive-compulsive disorder (OCD): An anxiety disorder in which the mind is flooded with persistent and uncontrollable thoughts or the individual is compelled to repeat certain acts again and again, causing significant distress and interference with everyday functioning.


obsessive-compulsive personality disorder: People with an obsessive-compulsive personality have inordinate difficulty making decisions, are overly concerned with details and efficiency, and relate poorly to others because they demand that things be done their way. They are unduly conventional, serious, formal, and stingy with their emotions.


occipital lobe: The posterior area of each cerebral hemisphere, situated behind the parietal lobe and above the temporal lobes, responsible for reception and analysis of visual information and for some visual memory.


Oedipus complex: In Freudian theory, the desire and conflict of the four-year-old male child who wants to possess his mother sexually and to eliminate the father rival. The threat of punishment from the father causes repression of these id impulses. Girls have a similar sexual desire for the father, which is repressed in analogous fashion and is called the Electra complex.


operant behaviour: A response that is supposedly voluntary and operates on the environment, modifying it so that a reward or goal is attained.


operant conditioning: The acquisition or elimination of a response as a function of the environmental contingencies of reward and punishment.


operationism: A school of thought in science that holds that a given concept must be defined in terms of a single set of identifiable and repeatable operations that can be measured.


opiates: A group of addictive sedatives that in moderate doses relieve pain and induce sleep.


opium: One of the opiates, the dried, milky juice obtained from the immature fruit of the opium poppy. This addictive narcotic produces euphoria and drowsiness and reduces pain.


oppositional defiant disorder: An under-controlled disorder of children marked by high levels of disobedience to authority but lacking the extremes of conduct disorder.


oral stage: In psychoanalytic theory, the first psychosexual stage, which extends into the second year; during this stage the mouth is the principal erogenous zone.


organismic variable: A physiological or psychological factor assumed to be operating "under the skin"; these variables are a focus of behavioural assessment.


orgasm (climax): The involuntary, intensely pleasurable, climactic phase in sexual arousal that lasts a number of seconds and usually involves muscular contractions and ejaculation in the male and similar contractions in the genitalia of the female.


orgasmic reorientation: A behaviour therapy technique for altering classes of stimuli to which people are sexually attracted; individuals are confronted by a conventionally arousing stimulus while experiencing orgasm.


outcome research: Research on the efficacy of psychotherapy. Contrast with process research.


outpatient commitment: A form of civil commitment whereby the person is not institutionalized, rather is allowed to be free in the community but under legal-medical constraints that ensure, for example, that prescribed medication and other measures are taken to maximize the chances of the patient being able to live outside of a mental hospital. Consistent with the principle of least restrictive alternative.


overcontrolled (behaviour): In reference to childhood disorders, problems that create distress for the child, such as anxiety and social withdrawal.