Double-blind experiments are those in which neither the researchers nor the subjects (human) know whether they are members of the experimental or control group. The importance of this procedure is critical in situations where psychological bias is likely to influence the results. If subjects know they are receiving a drug (especially one whose results are variable) they may well show more of the expected effects than if they do not know. The same is true for the researchers, who are more likely to tabulate results according to "expectations" if they know what treatment has (or has not) been administered.