Exogeny

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Exogenous (from the Greek words "exo" and "gignomi", meaning "outside" and "to come to be") refers to an action or object coming from outside a system. It is the opposite of endogenous, something generated from within the system.

• In attentional psychology, exogenous refers to reaction to external stimuli without conscious intention. An example of this would be attention drawn to a flashing light in the periphery of vision.

• In ludology, the study of games, exogenous refers to anything outside the game itself. Therefore an item in a massively multiplayer online game would have exogenous value if people were buying it with real world money rather than in game currency (though its in game cost would be endogenous).

• In an economic model, an exogenous change is one that comes from outside the model and is unexplained by the model. For example, in the simple supply and demand model, a change in consumer tastes or preferences is unexplained by the model and also leads to endogenous changes in demand that lead to changes in the equilibrium price. Similarly, a change in the consumer's income is given outside the model. Put another way, an exogenous change involves an alteration of a variable that is autonomous, i.e., unaffected by the workings of the model.

• In linear regression, it means that the variable is independent of all other response values.

• In biology, "exogenous" refers to an action or object coming from the outside of a system. For example, an exogenous contrast agent in medical imaging refers to a liquid injected into the patient intravenously that enhances visibility of a pathology, such as a tumor.

• In biology, an exogenous factor is any material that is present and active in an individual organism or living cell but that originated outside of that organism, as opposed to an endogenous factor.
  • Exogenous factors in medicine include both pathogens and therapeutics.
  • DNA introduced to cells via transfection or viral infection (transduction) is an exogenous factor.
  • Carcinogens are exogenous factors.

• In materials science, exogenous refers to a property of a substance which is derived from outside or external influences, such as a nano-doped material.

See also

• Endogenous

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