Person x Situation x System Dynamics

To the Editor:

A major task of psychological science is to explain behavioral variance, often by determining the extent to which observed behavior can be attributed to internal variables such as individual differences, to external situation-based variables, and to their interaction. A major difference between personality and social psychologists lies primarily in their emphasis on dispositional versus situational variables; rarely do they disagree on endorsing the inevitable interaction between them. My own research has involved the study of both social and personality factors in such varied areas as shyness, time perspective, hypnotizability, political behavior, and prisons.

In my book, The Lucifer Effect: Understanding How Good People Turn Evil (Random House, 2007), I make explicit that any analysis of complex human behavior demands a tri-part focus — for example: “What I learned from the SPE [Stanford Prison Experiment] paradigm about investigating institutional abuses is the need to evaluate various factors (dispositional, situational, and systemic) that lead to the behavioral outcomes we want to understand” (p. 330).  Further, I make explicit that “people and situations are usually in a state of dynamic interaction” (p. 8).

I never stated that “the situation trumps individual dispositions,” nor did I offer a “purely situational” explanation, nor ever assert there are “no bad apples.” It was the APS book reviewer who simplified and distorted my position by declaring, “The main argument in The Lucifer Effect is that there are no bad apples, only bad barrels. That is Zimbardo’s metaphor for the power of the situation to trump individual differences” (Herbert, 2007).

Rather, I presented an alternative to the “purely dispositional” conclusion that is common among the public, many psychologists, and in this case, the military and Bush administration civilian command (“it was just a few bad apples responsible for the Abu Ghraib abuses”). Instead, I present extended evidence why situational and especially systemic factors must also be taken into account. When understanding behavior in the real world, beyond our laboratories or classroom surveys and personality scale data collection, it is essential to begin with a systems level of top-down analysis because that is where the real power lies, along with the leverage to change situations and also person-perpetrators in those situations.

I find it deeply distressing that some of my colleagues would take the (mis)interpretation stated in a book review as the basis to accuse me of “distorting the scientific evidence.”  To the contrary, as an expert defense witness for the MP in charge of Tier 1A night shift (where the abuses occurred), I have done extensive research on the people and events at Abu Ghraib, and all the sources are well documented in my book (I especially want to note my detailed analyses of the various investigative reports).  Thus, my conclusions are not abstract conceptual ones, as these critics assert, but are based on the best available evidence that highlights the role of specific environmental risk factors in contributing to these abuses. The central issue is not the relative predictive power of person versus situation, rather it is the typical underestimation of situational factors and “channel factors” that lead to erroneous predictions and misattributions of behavior whenever such external factors are operating.

I hope that a careful reading of what I actually say in The Lucifer Effect, and not merely the allegations of a book reviewer, will defuse some of the alarm that these colleagues have about both my scientific integrity and my messages to the general public. Regardless of their reaction to this reply and to the more extended one to be found on my web site (, I will continue my lifelong mission of trying to give to the American and international public what I consider to be sound psychological science.

Philip Zimbardo
Stanford University

Dr. Zimbardo makes a good point. My 800-word review did oversimplify his 500-page book, perhaps inevitably so. And my paraphrase (“the situation trumps individual differences”) was not quite accurate. He wrote instead: “A large body of evidence in social psychology supports the concept that situational power triumphs over individual power in given contexts.” I wish now that I had used the word “triumphs” rather than “trumps” and added “in given contexts” to make clear Dr. Zimbardo’s interactionist position.
-Wray Herbert

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