Dictionary of Terms


Object Permanence The idea that objects do not disappear when they are out of sight.

Objective Personality Tests Tests for measuring personality that can be scored objectively, such as a multiple-choice or tue/false test.

Observational Learning Learning through observing the kinds of consequences others (called models) experience as a result of their behavior.

Obsession An involuntary recurring thought, idea, or image.

Obsessive-Compulsive Disorder Recurrent, unwanted thoughts or ideas and compelling urges to engage in repetitive ritual-like behavior.

Occipital Lobe The rearmost portion of the cerebral cortex; contains the primary visual cortex.

Olfaction The sense of smell.

Olfactory Mucosa The mucous membrane lining the top of the nasal sinuses; contains the cilia of the olfactory receptors.

Operant Chamber An apparatus in which an animalís behavior can be easily observed, manipulated, and automatically recorded. Sometimes called a "Skinner Box."

Operant Conditioning A form of learning in which behavior is affected by its consequences. Favorable consequences strengthen the behavior and unfavorable consequences weaken the behavior.

Operational Definition The definition of a variable in terms of the operations the experimenter performs to measure or manipulate it.

Opioid A neuromodulator whose action is mimicked by a natural or synthetic opiate, such as opium, morphine, or heroin.

Opponent Process The representation of colors by the rate of firing of two types of neurons: red/green and yellow/blue.

Optic Disk A circular structure located at the exit point from the retina of the axons of the ganglion cells that form the optic nerve.

Optimal Level of Skill Performance According to Fischerís Skill Model, the brainís maximal capacity for information processing.

Optimum-Level Hypothesis The hypothesis that organisms will perform behavior that restores the level of arousal to an optimum level.

Oral Stage The first of Freudís psychosexual stage, during which the mouth is the major source of physical pleasure. Early in this stage, the mouth is used for sucking; later in the stage it is used for biting and chewing.

Orbitofrontal Cortex A region of the prefrontal cortex that plays an important role in recognition of situations that produce emotional responses.

Organizational Effect An effect of a hormone that usually occurs during prenatal development and produces permanent changes that alter the subsequent development of the organism.

Orienting Response Any response by which an organism directs appropriate sensory organs (eyes, ears, nose) toward the source of a novel stimulus.

Ossicle One of the three bones of the middle ear (the hammer, anvil, and stirrup) that transmit acoustical vibrations from the eardrum to the membrane behind the oval window of the cochlea.

Oval Window An opening in the bone surrounding the cochlea. The stirrup presses against a membrane behind the oval window and transmits sound vibrations into the fluid within the cochlea.

Overextension The use of a word to denote a larger class of items than is appropriate, for example, referring to the moon as a ball.

Overtone The frequencies of complex tones that occur at multiples of the fundamental frequency.

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