awareness and cognition. It seems clear that in some cases there is a large effect that experimenters did not anticipate, that is due to participants' reactions to the experiment itself. So as a methodological heuristic, it is useful, but as an exact predictor of effects, it is not: it is difficult to ascertain the Hawthorne effect in every situation. To understand when and why we will see a Hawthorne or experimenter effect, we need more detailed