The SPE has been criticised for having strong , which is where participants act the way they think the researchers want them to act. In an experiment to test the extent of the demand characteristics in the SPE, Banauzzi and Mohavedi asked 150 students to predict the results of the SPE, and 89.9% predicted that the 'guards' would act in an oppressive, hostile nature towards the 'prisoners'. So, the participants in the experiment could also have predicted how they were supposed to act, and act in this way, to please the researchers. 