AO3

• weakness is that most guards said they were acting as their behaviour may not have been influenced by the same factors which effect behaviours in real life which means there is low ecological validity
• a weakness is that it lacks population validity as they only used US male students so the finding cannot be generalised to women or those from other countries
• a weakness is the ethical issues as there was a lack of fully informed consent as the participants didn't agree to be arrested from their homes and Zimbardo didn't stop the experiment when it was getting to the point of abuse
• a strength is that it has high internal validity as there was a high control over variables because they screened for emotionally stable individuals and then randomly allocated roles which rules out at individual personality differences. this means that there is a high credibility of the research
• a strength is that the harmful treatment of the participants has lead to form recognition of ethical guidelines by the American Psychology Association and studies now have to go under a lot of review before the board before they can begin