Zimbardo’s conclusions didn’t take into account a crucial aspect of the study: how the participants were recruited. To find prisoners and guards, researchers placed this ad in the local newspaper: Male college students needed for a psychological study of prison life. $15 per day for 1–2 weeks beginning August 14th. For further information and applications, contact . . . In 2007, researchers at Western Kentucky University noticed a small, seemingly insignificant detail about that ad. It made them wonder whether it had inadvertently skewed the study. To find out, they replicated that ad, only changing $15 to $70 (to adjust for inflation since the 1970s). Every other word in the updated ad was identical. Then, they created a new ad. It was the same in every way, with one key difference: it replaced the line “for a psychological study of prison life” with the phrase “for a psychological study.” In some college towns, they placed the “prison life” advertisement. In others, they placed the “psychological study” ad. The idea was to have one group that volunteered for a prison experiment and another group that volunteered for a generic psychology study. Would there be any difference between the people who responded? Once the recruitment period closed, the researchers invited the prospective participants in for psychological screening and a thorough personality evaluation. What they found was extraordinary. Those who responded to the prison experiment advertisement scored significantly higher on measures of “aggressiveness, authoritarianism, Machiavellianism, narcissism, and social dominance and significantly lower on dispositional empathy and altruism” compared to the generic study.
Just by including the word prison in the advertisement, they ended up with a disproportionately sadistic batch of students.
Corruptible: Who Gets Power and How it Changes Us, Brian Klaas (UK) (US)