Final answer:
Philip Zimbardo used an experimental research method in his study of prison behavior known as the Stanford Prison Experiment, which involved a controlled environment and random assignment of roles.
Step-by-step explanation:
In his study of prison behavior, Philip Zimbardo utilized a research method known as an experiment. Specifically, it was a controlled experiment conducted in a simulated environment to study the psychological effects of prison life. This groundbreaking study is formally known as the Stanford Prison Experiment. Zimbardo's approach involved randomly assigning volunteer participants to the roles of prisoners or guards to explore the impact of situational variables on behavior. The significance of random assignment in this context was to ensure that pre-existing differences between participants did not influence the outcomes, which is a key tenet of experimental design.
This experiment was intended to run for two weeks but was terminated after just six days due to the extreme and distressing changes observed in the participants' behaviors. The results of the experiment have been widely discussed and criticized in terms of ethics and methodology and continue to be a focal point for discussions about the influence of power and authority on human behavior.