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Even the most humanely designed prisons have negative effects on the people living and working inside. (Shutterstock)

What a widely attacked experiment got right on the harmful effects of prisons

The Stanford Prison Experiment is one of the few scientific studies to enter the public consciousness through mainstream news, documentaries, popular books, a TED talk and a major motion picture.

Recently, it has been making headlines in a very bad way.

In 1971, Stanford University psychology professor Philip Zimbardo sought to evaluate the prison’s impact on human behavior. He randomly assigned normal, healthy, emotionally stable male college students (without criminal records) to be “prisoners” or “guards” in a fake prison.

Newspaper advertisement for participants for the Stanford Prison Experiment. (

Within six days, Zimbardo ended the experiment. The “guards” were torturing the “prisoners,” and the “prisoners” were rebelling or experiencing psychological breakdown.

In news articles, the Stanford experiment has been “debunked” and “exposed as a fraud.” Its findings have been declared “very wrong” and “fake.” It has been further criticized for experimenter interference, faked behaviour from participants and for research design problems, among other things.

These serious critiques have generated much discussion in academic circles and in news articles about what, if anything, we can learn from the experiment.

And yet, as someone who studies prisons, I’m struck by how much the Stanford Prison Experiment got right. A wealth of other research suggests prisons have serious detrimental effects on prisoners and prison workers alike.

What the research says

Living and working in prison is extremely stressful and demoralizing.

Some people are better at repelling these effects than others. Even so, prisoners and prison workers suffer from high rates of depression, anxiety, suicide, PTSD and other devastating conditions. For many prisoners, these conditions continue after prison and can be worsened by the transition into the free world.

We have long known that prisons are damaging places for both prisoners and prison workers. In his 1956 book, Society of Captives, Princeton sociology professor Gresham Sykes explained that incarceration deeply injured prisoners’ dignity and self-concept. He also described how prison officers became “corrupted” by the prison environment with its contradictory imperatives, impossible-to-enforce rules and necessary compromises.

In the 60 years since Sykes’ book, research in diverse prison settings has confirmed and expanded upon many of his findings.

The role of prison design

Storstrøm Prison, which opened in Denmark in 2017, is said to be the world’s most humane prison. (C.F. Møller/Torbin Eskerod)

These insights extend beyond contemporary prisons in the United States. Prisons in Norway, Sweden and Denmark, known for their humaneness, also cause harm.

Indeed, smart designs can lessen, but not destroy, the prison’s negative impacts. But since the 1970s, in many Western countries, the main goal when designing prisons has been containment and security, not prisoners’ physical and mental health.

Popping up in the U.S. in the 1980s and 1990s, supermaximum security prisons (Supermaxes), which contain prisoners in solitary confinement in small concrete cells for 23 hours a day, are a particularly harmful design.

Read more: Broken system: Why is a quarter of Canada's prison population Indigenous?

Prisoners react differently to these Supermax prison regimes. Some are able to withstand the conditions, others break down within hours of their arrival. We do not yet fully understand why people react differently, but we do know that Supermax prisons have an array of negative impacts on prisoners’ mental health including hallucinations, self-harm and permanent psychological damage.

Not just prisoners

Prison staff are also affected. The history of American imprisonment is also filled with examples of people with good intentions becoming “corrupted” by the prison.

In this April 12, 2016 photo, a visitor makes a photograph of a cellblock at Eastern State Penitentiary in Philadelphia. The nearly two-century-old penitentiary is now a historic site. (AP Photo/Matt Rourke)

Pennsylvania’s Eastern State Penitentiary opened in 1829. Progressive Philadelphia penal reformers designed Eastern to be more humane than other prisons, with prisoners’ physical and mental health in mind. They implemented a routine — combining work, education, mentorship and outdoor exercise — to benefit both prisoners and society. Finally, they sought to protect prisoners’ identities so they could reenter society without stigma.

Within five years of the prison’s opening, however, the penal reformers, now prison administrators, had betrayed their humanitarian goals.

They bent the rules, out of necessity or convenience, so the prison functioned smoothly. In the process, they sacrificed the regime’s humanitarian and prisoner-focused elements.

Eastern’s administrators authorized torture, including what we now call waterboarding, held misbehaving prisoners after their sentences had expired until they apologized and justified these actions as beneficial to prisoners.

These gaps between theory and practice, including the use of torture punishments, were common at other American prisons in the 19th century and into the 20th. Other penal reformers–turned-administrators engaged in similar malfeasance despite their apparently genuine commitment to humanitarian values.

The situation was even more dire at prisons that were explicitly designed to be punitive and lacked Eastern’s humanitarian motivations.

Beyond the Stanford experiment

Even including these past failures, modern prisons rarely devolve as quickly and decidedly into a den of overt torture and serious mental breakdown as seen in the “Stanford Prison.”

In this Sept. 10, 1971 file photo, inmates wearing cloaks and football helmets stand behind bars in a corridor leading to D block as they begin negotiatiations with New York State officials after a prison uprising at Attica State Prison, in Attica, N.Y. (AP Photo/Bob Schutz, File)

It does happen — the Abu Ghraib torture scandal and the retaking of Attica Prison following the 1971 riot are graphic illustrations of how prison can unleash the worst of human nature with terrible consequences — but such extreme cases remain rare. Prisons’ negative effects are typically less dramatic and do less to capture the public imagination.

There is something about prisons that is damaging. But what is it?

Even the most humanely designed prisons have negative effects on the people living and working inside. And that is the deep truth we are still seeking to understand and the Stanford Prison Experiment effectively illustrates.

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