The Hawthorne effect in experimental research is the unwanted effect of the experimental operations themselves. Following the Hawthorne studies, various explanations have been proposed to account for rising rates of production. Although in the Relay Assembly Test Room experiment the experimental operations may have produced other extraneous variables, a reexamination based on new and neglected evidence has yielded a new interpretation. The new variable, made more plausible because research in other contexts has shown it to have similar effects, is a combination of information feedback and financial reward. It is an example of the control of behavior by its consequences. Although several approaches may be taken to explain the effects of response-consequence contingencies, I have favored operant conditioning because it seems to account for progressive increases in response rate-the Hawthorne phenomenon. Generalizing from the particular situation at Hawthorne, I would define the Hawthorne effect as the confounding that occurs if experimenters fail to realize how the consequences of subjects' performance affect what subjects do. But the Hawthorne effect need not be viewed solely as a problem in conducting experiments. The phenomenon that created it should be studied in its own right, as Sommer (67) suggested with a different phenomenon in mind. The study of response-consequence contingencies might well be extended to the examination of motivation in industrial workers.