LEWISBURG — What would you do if someone asked you to inflict pain on an innocent person? You might say you’d refuse. You might say you’d be offended and outraged at the mere suggestion that you would be capable of something so inhumane.

Then again, you might just do it.

At least, that’s what Philip Zimbardo thinks — and he’s got proof that it’s possible that no matter how “good” a person is, he or she is capable of becoming “evil” quicker than you think.

Mr. Zimbardo is professor emeritus of psychology at Stanford University, where he has worked since 1968. He previously taught at Yale, New York University and Columbia. Mr. Zimbardo is known for his work on the abuse of prisoners in the Stanford Prison Experiment and his current commentary on the abuse of Iraqi prisoners at Abu Ghraib. He gave the talk, “The Lucifer Effect: Understanding how Good People turn Evil,” on Tuesday at Bucknell University.

Early on in his presentation Mr. Zimbardo asked the standing-room-only audience to consider how well each individual knows his or herself.

“How sure are you of what you would or would not do in certain situations?” he asked. “How well does anyone really know anyone?

His goal for the evening, he said, was to get everyone in the room to transform their own self-perception.

“I want you to steer away from thinking ‘but not me’,” he said.

In order to show just how a typically “normal” or “good” person can become evil based merely on outside influences, Mr. Zimbardo pointed to the recent case of abuse of Iraqi prisoners at Abu Ghraib.

He said a good person performing seemingly evil acts happens because of dispositional, situational and systemic influences.

Take Army Reserve Staff Sgt. Chip Frederick, for example. Sgt. Frederick was in charge of the prisoners at Abu Ghraib. Before his duty there, he was, by all accounts, a “super-patriot.” He earned numerous medals and awards and was seen to be “average.”

Fast-forward months after he was put in charge of the prison in 2004 where he is seen in photographs torturing prisoners. He is wearing a painted face and has admittedly hit, kicked, punched and committed unspeakable acts of torture against prisoners.

Mr. Zimbardo, who became a part of Sgt. Frederick’s defense team, testified that it was the situation Sgt. Frederick was put in that caused the behavior. He was merely a victim of his surroundings — working insanely long shifts for weeks at a time, eating and sleeping in the prison and being given no training or supervision by higher officers.

It doesn’t excuse what he did, Mr. Zimbardo said, but it does explain it.

Blind obedience to authority plays a role in what turns good people bad, too, he said.