In Zimbardo's prison study, male college students agreed to participate in a 2-week experiment to discover what would happen when they took on the roles of prisoners and guards. After the prisoners staged a revolt, the researchers found that .

the guards became more aggressive.

Explanation:

Psychologist Philip Zimbardo and his colleagues conducted an experiment to figure out if the violence documented by guards in American prisons was due to their sadistic nature or had something to do with the prison environment. Although prisoners and guards were permitted to communicate in any way they chose, the encounters were violent and therefore some volunteers have to be released soon. The guards started to act in ways that were violent and hostile towards the prisoners, whilst the prisoners became passive and discouraged.

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