I took Intro to Psychology in my mid to late twenties. We were required to participate in a study as part of the class. IIRC, the study was being performed by a grad student in pursuit of their degree. So, really, both the "scientist" and subjects of the study were kind of compelled to participate. No one was there of their free will. We were all trying to tick off an educational checkbox on our way to a sheepskin in…
Related - the rat experiment described in http://calteches.library.caltech.edu/51/2/CargoCult.htm