Observer Expectancy Effect

If you have ever worked in a research lab, you’re probably quite familiar with this phenomenon. A key factor of research design is figuring out how to avoid accidentally influencing participants. For example, if you’re running a study examining the effects of a certain new medication on participants’ stress levels, you’ll probably expect participants receiving the medication to be less stressed than those receiving a placebo pill. Even if the participants all think they’re receiving the actual medication, you might unconsciously treat the two groups differently. Since you expect the placebo group to be more stressed, you might treat them like they are more stressed, which may cue them to act more tense than they normally would. On the other hand, you’ll expect participants getting the real medication to be less stressed and treat them like they’re more relaxed or ask them leading questions that hint that they should be more relaxed. In this way, you may affect the behaviors of both groups, ultimately compromising the accuracy and generalizability of your results.