Final answer:
The design factor that would most likely result in lower obedience rates in a study modeled after Stanley Milgram's would be to have the participant feel fully responsible for the victim's welfare. This approach utilizes findings from variations of Milgram's experiments, which indicate decreased obedience when participants' empathy and personal responsibility are heightened.
Step-by-step explanation:
To reduce or lower the obedience rates found by Stanley Milgram in an obedience study, the design would need to focus on factors that have been historically shown to decrease obedience. Milgram's experiment found that a significant number of participants were willing to administer what they thought were lethal electric shocks to others when directed by a person of authority. From Milgram's variations of his own study, we know that increasing the victim's humanity or reducing the perceived legitimacy of the authority figure reduces obedience rates.
Given the options, the factor most likely to generate lower obedience rates would be to have the participant feel fully responsible for the victim's welfare. This design choice leverages the evidence that when participants are made more acutely aware of the consequences of their actions on the victim, their obedience to authority figures that instruct harmful actions tends to decrease. Such a change can enhance the participants' sense of personal responsibility and empathy for the victim, which are powerful motivators against blind obedience to authority.