Object Permanence  

The understanding that objects exist even when they are not directly observed.

Objective Techniques   

A generic term for the psychological procedures used to measure personality which rely on measurable or objective techniques such as the MMPI-2 and WAIS-III.

Obsession   

A persistent and seemingly uncontrollable thought.

Occipital Lobe

One of for lobes of the brain.  Contains the visual cortex and therefore plays a major role in the interpretation of visual information.

Odd-Even Reliability

The correlation coefficient determined by comparing odd items of the measurement to the even items.  One method to determine the internal consistency of a test or measuring device.

Olfaction  

The sense of smell.

One-Way ANOVA

An Analysis of Variance used when there is only one main effect.

Operant Conditioning  

Learning that occurs due to the manipulation of the possible consequences.

Optimal Level of Arousal

Theory arguing that humans are driven to increase or decrease arousal to produce a comfortable level that is not over- nor under stimulating.

Oral Aggressive Personality

Stemming from the Oral stage, a child who becomes fixated due to over stimulation transfers his or her unresolved oral issues into aggression and hostility.

Oral Receptive Personality

Stemming from the Oral stage, a child who becomes fixated due to under stimulation transfers his or her unmet oral needs into smoking, drinking, talking, biting fingernails, or sucking one's own thumb, for example.

Oral Stage

Freud's first stage of psychosexual development where the primary sexual focus is on the mouth through sucking, tasting, and verbalizing.

Order Effects

The effects of administering treatments in a particular order

Ordered Array

A table consisting of data in order of highest to lowest or lowest to highest where each data is given a numbered rank depicting it's difference from the highest or lowest score

Ordinal Scale

Any scale that reflects only magnitude but does not contain equal intervals or an absolute zero 

Overlearning   

A technique used to improve memory where information is learned to the point that it can be repeated without mistake more than one time.