Definition of Expectancy Effect

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Expectancy Effect. PM Images / Getty Images

Definition: An expectancy effect is a psychoactive effect that happens in response to a person's expectation that a drug effect will occur. Expectancy effects include the placebo effect, and and can emphasize the perception of drug effects.

Pronunciation: ex-bek-tan-see

Examples: People experience an expectancy effect when they consume plain grapefruit juice, that they think contains alcohol, and feel intoxicated.

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