<P> Responses to this are partly dependent on whether the reader has already encountered the standard trolley problem (since there is a desire to keep one's responses consistent), but Unger notes that people who have not encountered such problems before are quite likely to say that, in this case, the proposed action would be wrong . </P> <P> Unger therefore argues that different responses to these sorts of problems are based more on psychology than ethics--in this new case, he says, the only important difference is that the man in the yard does not seem particularly "involved". Unger claims that people therefore believe the man is not "fair game", but says that this lack of involvement in the scenario cannot make a moral difference . </P> <P> Unger also considers cases which are more complex than the original trolley problem, involving more than just two results . In one such case, it is possible to do something which will (a) save the five and kill four (passengers of one or more trolleys and / or the hammock - sleeper), (b) save the five and kill three, (c) save the five and kill two, (d) save the five and kill one, or (e) do nothing and let five die . </P> <P> In 2001, Joshua Greene and colleagues published the results of the first significant empirical investigation of people's responses to trolley problems . Using functional magnetic resonance imaging, they demonstrated that "personal" dilemmas (like pushing a man off a footbridge) preferentially engage brain regions associated with emotion, whereas "impersonal" dilemmas (like diverting the trolley by flipping a switch) preferentially engaged regions associated with controlled reasoning . On these grounds, they advocate for the dual - process account of moral decision - making . Since then, numerous other studies have employed trolley problems to study moral judgment, investigating topics like the role and influence of stress, emotional state, different types of brain damage, physiological arousal, different neurotransmitters, and genetic factors on responses to trolley dilemmas . </P>

The principle of double effect which we talked about with the trolley car problem asserts that