O

Object Relations Theory: developed from the work of Neo-Freudian Melanie Klein, this deals with the way relationships between the young child and his/her 'love objects' are represented and the effect this has on the way the child develops through into adulthood.

Observational Learning: see vicarious learning.

Obsessive-Compulsive Disorder (OCD): a serious condition characterised by undesirable - sometimes highly-disturbing - and intrusive thoughts and compulsive, often ritualistic behaviours. The behaviours, though not always obviously so, serve to compensate for, control or distract from the unwanted thoughts.
Clare W Graves saw OCD as the result of emerging BLUE fighting back the impulses of RED which would fit with Carl Gustav Jung's assertion that OCD was the intrusion into consciousness of threatening sexual and aggressive ideas being warded off through ritualistic behaviours and/or repeated verbal incantations.
At a biological level OCD has been associated with problems in the caudate nucleus affecting signalling between the orbitofrontal cortex and the thalamus.

Occasionalism: a philosophical theory about causation which says that created substances cannot be efficient causes of events. Instead, all events are taken to be caused directly by God. (A related theory, which has been called 'occasional causation', also denies a link of efficient causation between mundane events but may differ as to the identity of the true cause that replaces them.) The theory states that the illusion of efficient causation between mundane events arises out of God's causing of one event after another. However, there is no necessary connection between the two: it is not that the first event causes God to cause the second event: rather, God first causes one and then causes the other.

Oestregen: oestrogens, are a group of compounds named for their importance in the oestrous cycle of humans and other animals. They are the primary female sex hormones.

While oestrogens are present in both men and women, they are usually present at significantly higher levels in women of reproductive age. They promote the development of female secondary sexual characteristics, such as breasts, and are also involved in the thickening of the endometrium and other aspects of regulating the menstrual cycle. In males, oestrogen regulates certain functions of the reproductive system important to the maturation of sperm and may be necessary for a healthy sex drive.

Operant Conditioning: first identified conceptually by Edward Thorndike (1932), this is leaning through the consequnces of behaviour - either reinforcement (reward) or punishment. (Thorndike talked of "stamping in" and "stamping out" behaviour.) See also Behaviourism.

Orbitofrontal Cortex: a part of the frontal lobe of the cerebral cortex associated with learning.

Organisation LifeCycle: the theory that organisations, like biological organisms, are born, grow, mature, decline (age) and die arguably had its foundation in Mason Haire’s classic ‘Modern Organisation Theory’  (1959).

Larry R Greiner (1972)  advanced the concept considerably; but it is almost beyond argument that Ichak Adizes (1989) has provided the most complete ‘map’ of organisational development to date. His work is based on extensive research in the field.