Experiments have long been the method of choice in psychology. However, the exp

One limitation of experiments is experimenter effects.  That is, if subjects know whether they are in the experimental or control group their expectations may affect the results.
A researcher’s expectations can also influence the results of an experiment.
If participants are not representative of the larger population of interest, the results cannot be generalized.
Controlled experiments may result in artificial situations in which behavior is not normal and cannot be generalized to the real world.
Field research can at least partially overcome this last objection.

Experiments allow researchers to control the situation being studied, manipulate an independent variable, and assess the effects of the manipulation on a dependent variable. All research in psychology must conform to ethical guidelines. (See the Web Essay question #3 in the Study Guide.) This is especially true when conducting studies using an experiment. Experimental studies usually require a comparison or control condition, and often involve random assignment of subjects to experimental and control groups. In some studies, control subjects receive a placebo. Single-blind and double-blind procedures can be used to prevent the expectations of the subjects or the experimenter from affecting the results. Because experiments allow conclusions about cause and effect, they have long been the method of choice in psychology. However, like laboratory observations, experiments create a special situation that may call forth behaviour not typical in other environments. Many psychologists, therefore, have called for more field research.