Expectations, motivations and task demands (Reisberg, ch. 11, methods)

In most experiments, we're trying to study how people behave under natural circumstances-how they behave when they're just being themselves. As a result, it is crucial that we take steps to minimize the demand characteristics of a study.

As the textbook chapter describes, the term experimental demand refers to any cues in the experiment that might signal to participants how they "ought to" behave. In some cases, the demand indicates to participants what results the researcher hopes for (that is, results that would confirm the researcher's hypothesis), and this may encourage participants to make the hoped-for response, even if they're inclined toward some other option. In other cases, experimental demand somehow suggests that certain responses are more desirable than others-so that, for example, participants perceive some responses as indicating greater intelligence, or greater sensitivity. And, of course, it's plausible that participants will choose these responses to avoid appearing stupid or insensitive.

What can we do to avoid these effects, so that we don't guide participants toward some particular response, but instead observe participants as they normally are? Researchers use several different strategies. First, we do all we can to make sure that experimental demand never arises in the first place. Thus, we make sure that the procedure contains no signals about what the hypothesis is, or which group is receiving the experimental treatment and which group is the control. Likewise, we do what we can to phrase our questions, and cast the response options that are available, so that no responses seem preferable to any others.

Second, if participants focus their attention on the experimental manipulation, they may be too cautious or too deliberate in how they respond. Worse, they may develop their own notions about how they're "supposed to" respond to this manipulation. (See pp. 373-374 in Chapter 11 in the textbook for an example of this.) To avoid these concerns, most experiments avoid drawing any attention to the experiment's main manipulation; indeed, many experiments provide a "cover story" about what the experiment is about, seeking to draw attention to some other aspect of this procedure. In this way, we maximize the chance that during the experiment, participants will behave naturally and spontaneously in response to the manipulation.

Third, we do what we can to make sure that all participants in all conditions receive exactly the same treatment. Thus, we make sure to encourage all participants in the same way, give them similar instructions, and so on. In some cases, we rely on a double-blind procedure, in which neither the participant nor the person administering the procedure knows what the experiment is about, or which comparison group the participant is in. This ensures that the administrator won't be more encouraging, or more forceful, with one group in comparison with the other; it also guarantees that all participants will have the same expectations about the experiment.

Can we make certain that participants' expectations, goals, and hypotheses play no role in shaping our data? Probably not, and this is one of the reasons why replications (with other participants and other procedures) are so important. Even so, we do what we can to minimize the contribution of these factors, and so make it far more likely that our results can be understood in the terms we intend.