What An Experiment at Stanford Taught Us About Human Behavior

The Stanford Prison Experiment

In 1971, a group of researchers leads by psychology professor Philip Zimbardo was studying the psychological effects of becoming a prisoner or prison guard.

Zimbardo and his team aimed to test the hypothesis that the inherent personality traits of prisoners and guards are the chief cause of abusive behavior in prison.

18 psychologically stable and healthy, male participants (students) were recruited and told they would participate in a two-week prison simulation. The group was intentionally selected to exclude those with any criminal background, psychological impairments, or medical problems.

The Stanford prison experiment

The experiment was conducted in the basement of Jordan Hall (Stanford’s psychology building). 9 out of the 18 participants were assigned the role of prisoner, while the other 9 were assigned the role of the prison guards.

Blind-folded prisoner with guards in the Stanford Prison Experiment
A blind-folded prisoner with guards.

Zimbardo designed the experiment in order to induce disorientation, depersonalization, and deindividualization in the participants.

The guards were provided with batons to establish their status, clothing similar to that of an actual prison guard, and mirrored sunglasses to prevent eye contact.

They were instructed not to physically harm the prisoners or withhold food or drink, but were allowed to take away the prisoners’ individuality in various ways and leads to a sense of powerlessness in the prisoners.

“In this situation, we’ll have all the power and they’ll have none.” Zimbardo can be seen talking to the guards in the footage of the study.

Prisoners wore uncomfortable smocks and stocking caps, as well as a chain around one of their ankle. They were called by their assigned numbers, sewn on their uniform, instead of their name.

To make the experiment as close to the actual prison as possible, the prisoners were “arrested” at their homes and “charged” with armed robbery, then conducted full booking procedures before transported to the mock prison and given their new identities.

The experiment was stopped after 6 days

On August 20, 1971, Zimbardo was forced to announce the end of the experiment, because the participants adapted to their roles well beyond Zimbardo’s expectations, as the guards enforced authoritarian measures and ultimately subjected some of the prisoners to psychological torture.

Many of the prisoners passively accepted the psychological abuse, and readily harassed other prisoners who attempted to prevent it, at the request of the guards.

Even Zimbardo himself was affected and consumed by the experiment, in his role as the superintendent, permitted the abuse to continue. Two of the prisoners have to quit the experiment early.

The entire experiment was unexpectedly stopped after only six days, because of the objections of a researcher in the team. The results of the experiment favor the situational attribution of behavior rather than dispositional attribution.

Simply put, it seemed that the situation, rather than their individual inherent personalities, caused the participant’s behavior. It also used to illustrate and explain the power of authority.

The roles we all play in life

When you think about it, our life is very similar to (or even the same as) the experiment.

We’re playing one or many roles – as a father/mother, citizen, or employee – from day to day. In most cases, we don’t decide what role we’re playing and who we are; sometimes, we don’t even have the choice for some role such as a son, a citizen of a certain country and a part of a certain race.

Often, our environment and circumstances decide who we are and what we do. It also indirectly shapes our beliefs and identity at the same time.

If we believe we can never be successful and then define ourselves as a failure, we will be quickly consumed by the situation. It’s not about the situation that can’t be changed, but more on our behavior in believing we can do nothing to change. In other word, we learned helplessness.

. . .

During the end of the Stanford Prison Experiment, Zimbardo invited a Catholic priest who had been a prison chaplain to evaluate how realistic our prison situation was, by interviewing each prisoner individually.

The only prisoner who did not want to speak to the priest was Prisoner 819, who was feeling sick, had refused to eat.

While Zimbardo was talking to him to see what doctor he need to see, he started breaking down and crying hysterically. Zimbardo then took off the chain around his ankle and his cap decided to withdraw from the experiment to see the doctor.

While he was doing this, one of the guards lined up the other prisoners and had them chant aloud: “Prisoner 819 is a bad prisoner!”

As prisoner 819 heard the chanting, he started sobbing uncontrollably and refused to leave. Even he was sick, he wanted to go back to the cell to prove he’s not a bad prisoner.

Zimbardo then said, "Listen, you are not 819. You are [his name], and my name is Dr. Zimbardo. I am a psychologist, not a prison superintendent, and this is not a real prison. This is just an experiment, and those are students, not prisoners, just like you. Let's go."

The prisoner 819 stopped crying suddenly, looked up at Zimbardo like a small child awakened from a nightmare, and replied, "Okay, let's go."

The hidden pillars that shape our beliefs

We all face the same situation in real life. We’re trapped in our own state of mind that seems impossible to get out of it. But is it true that our situation is the sole factor that leads to our behavior?

Imagine there is a table in front of you, with only two legs. What is going to happen? It falls. It will never be able to stabilize. Now, add one more legs, it gets much stable. Add another one, now it’s a table.

What about adding another 10? It will be really stable, and you can place a heavier object on top of it. That’s exactly how our belief works. The tabletop is a belief, but what we do not know is that we need those pillars/legs to support it, which is the evidence.

How our belief works, illustrated by Dean Yeong.
How our belief works, illustrated by Dean Yeong.

Without the shreds of evidence, your belief is just some destructible ideas.

That’s how people used to believe that the earth is flat and we’re the center of the solar system. And that’s exactly how those crazy ones believe we will be able to fly one day!

But what happens when we have strong pieces of evidence to support our beliefs? Just like how Zimbardo carried out the experiment that makes the role play as real as possible for both prisoners and prison guards.

Every aspect of that experiment was carefully designed to match the real prison environment. That makes the participants believe they are who their roles are (prisoner or prison guard) until they accept that role as a part of their identity.

Beliefs are the building blocks that shape our identity.

The belief-behavior loop: a self-fulfilling prophecy

Rather concluding that the circumstances shape our behavior at a deeper level compared to our individual inherent personalities, I personally think it works as a loop.

Our circumstances and outcomes build and create pieces of evidence to strengthen our beliefs in the first place that lead to the formation of our identity.

In the second phase of the loop, our identity forms our behavior and thus the results that finally become another piece of evidence to strengthen a particular belief again.

Behavior loop by Dean Yeong

There is always outcomes we can’t avoid and change in our life, but to achieve great results, most of us are fighting with the odd. Even successful people have constraints on the situation, their own set of challenges and bad behaviors to break.

I wrote about the impact of identity formation in a few articles before. As mentioned, to break any destructive behavior, we need to first alter our identity.

Here are a few ways to do so especially for those who are living in a situation that seems impossible to change.

Tell yourself the right story

Your beliefs are your perception of the situation. Understand that your situation means nothing without you give it a meaning. In other word, you create the story based on the situation.

Some see failure as the end of the world, some see it as a personal weakness, and some see it as a lesson and experience to learn and expand. Learn how to manage your perception of the situation will first filter through beliefs that form in your head.

Break the pattern and develop new habits

Habits affect our life in an impactful way beyond our imagination. It doesn’t only appear in your day-to-day actions that lead to the results but also embed in our head mentally and psychologically.

The way we think, the emotions we feel, the perceptions we instantaneously default to are habits too, and they affect our life more than our actions because it takes place before our actions. To change your behavior, you first need to break yourself out of the habits that form a destructive identity.

Take tiny actions to change your outcome

While the solutions I mentioned above are done mentally and psychologically, there is still time we’re unsure about the situation and loss of our minds.

When in doubt and confuse, the best way is to take tiny actions that create small changes. It may seem helpless again to do so, but these small actions are what create a bigger impact in the long run.

That indirect became the results and appearance we achieve or receive, which means the change of the situation. Hence, it is going to change your beliefs and identity. If you can’t manage the first phase of the loop, then work it out slowly in the second phase.


  1. I was inspired to write this article by a question on Quora: What are some psychology facts that people don't know? One of the answers there pointed me to discover more about the Stanford Prison Experiment.
  2. Story and images of the Stanford Prison Experiment are from prisonexp.org.

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