When the objects to be measured are influenced by the process of measurement, measurement becomes less reliable. Measurement becomes much less reliable the more its object is human activity, since the objects—people—are self-conscious, and are capable of reacting to the process of being measured. And if rewards and punishments are involved, they are more likely to react in a way that skews the measurement’s validity. By contrast, the more they agree with the goals of those rewards, the more likely they are to react in a way that enhances the measurement’s validity.
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