American Psychologist, vol. 74, no. 7, 2019, pp.823-839.
The Stanford Prison Experiment (SPE) is one of psychology’s most famous studies. It has been criticized on many grounds, and yet a majority of textbook authors have ignored these criticisms in their discussions of the SPE, thereby misleading both students and the general public about the study’s questionable scientific validity. Data collected from a thorough investigation of the SPE archives and interviews with 15 of the participants in the experiment further question the study’s scientific merit. These data are not only supportive of previous criticisms of the SPE, such as the presence of demand characteristics, but provide new criticisms of the SPE based on heretofore unknown information. These new criticisms include the biased and incomplete collection of data, the extent to which the SPE drew on a prison experiment devised and conducted by students in one of Zimbardo’s classes 3 months earlier, the fact that the guards received precise instructions regarding the treatment of the prisoners, the fact that the guards were not told they were subjects, and the fact that participants were almost never completely immersed by the situation. Possible explanations of the inaccurate textbook portrayal and general misperception of the SPE’s scientific validity over the past 5 decades, in spite of its flaws and shortcomings, are discussed.