a further weakness of zimbardo’s research is that there were major ethical issues. there was a lack of informed consent, as the prisoners did not consent to being arrested at their homes. in addition, there was a lack of right to withdraw, when one prisoner wanted to leave he spoke to zimbardo and had to ask to be ‘released’ from the prison, zimbardo responded as the superintendent, rather than an experimenter with a responsibility to the participant. finally, the prisoners were not protected from harm as some showed signs of psychological disturbance.COUNTER ARGUMENT:however, zimbardo carried out debriefing sessions with the participants for several years afterwards, and concluded that there were no long lasting negative effects.