A difficulty facing those who plan and review behavioral studies is the risk of harm of the subject. They believe that it can affect negatively on the physical and emotional aspect of the subject.
However, in behavioral and social science, physical and emotional harm is unlikely. The only purpose of experiments is to observe people's behavior. Most of the time, subjects do not know that they are part of an experiment because if they do know about it, they will probably change their behavior. They will only be informed as soon as the experiment is over. The results of social experiments and research will become insignificant and unreliable if subjects are aware beforehand.