Final answer:
Unexpected harm in the Stanford Prison Experiment led to the early termination of the study due to the severe emotional distress experienced by participants, illustrating the importance of ethical guidelines in research to prevent harm.
Step-by-step explanation:
The unexpected harm in psychological research studies, such as Rosenhan's study, arises from the negative psychological impact it can have on participants, which was a significant issue in several well-known psychology experiments. The Social Studies experiment that best fits the description of unexpected harm, however, is the Stanford Prison Experiment led by Philip Zimbardo. In this study, students were assigned roles as prisoners and guards in a simulated environment. The negative outcome of the experiment was so profound that it had to be terminated early due to the emotional harm suffered by participants, particularly the "prisoners," who experienced severe anxiety and hopelessness. Moreover, the guards engaged in increasingly sadistic behaviors, affecting both groups and necessitating the study's premature conclusion.
Such experiments have led to the establishment of ethical guidelines to prevent physical, financial, and especially emotional harm to participants. The importance of informed consent and consideration of potential harm has become paramount in psychological research, as evident by the reactions to controversial studies like Zimbardo's prison simulation and the Tuskegee syphilis study, where participants did not receive adequate treatment or information about their condition, causing harm beyond the scope of the study itself.