Back on the old blog, I wrote a series of posts in which I detailed a revolution in moral psychology. Sparked largely by recent empirical and theoretical work by neuroscientists, psychologists studying moral judgment have transitioned from Kantian rationalism, that goes back as far as, well, Kant (and in psychology, the Kantian Jean Piaget), to a more Humean approach, that considers emotion and motivation to be central.

Some of the more interesting work utilizing this new approach has been done by Joshua Greene and his colleagues1 They have demonstrated that we use different processes to make moral judgments about personal violations than about impersonal violations. Greene defines the two different types of violations as follows2:

A moral violation is personal if it is: (i) likely to cause serious bodily harm, (ii) to a particular person, (iii) in such a way that the harm does not result from the deflection of an existing threat onto a different party. A moral violation is impersonal if it fails to meet these criteria. (p. 519)

As an example of a moral dilemma that involves a potential personal violation, they use the famous footbridge problem, and as an example of a potential impersonal violation, they use the trolley problem. Here are their versions:

• Trolley: A runaway trolley is hurtling down the tracks toward five people who will be killed if it proceeds on its present course. You can save these five people by diverting the trolley onto a different set of tracks, one that has only one person on it, but if you do this that person will be killed. Is it morally permissible to turn the trolley and thus prevent five deaths at the cost of one?

• Footbridge: The trolley is headed for five people. You are on a footbridge over the tracks next to a large man. The only way to save the five people is to push this man off the bridge and into the path of the trolley. Is that morally permissible?

When presented with the footbridge problem, people almost always say that it is not permissible to push the man off the bridge, but when presented with the trolley problem, they almost always say that it is morally permissible. It seems as though participants tend to use utilitarian principles to make judgments in the trolley problem, but not in the footbridge problem. Greene and his colleagues explain this difference by arguing that potential personal violations elicit an emotional response, while impersonal violations allow us to use more cognitive processes (perhaps reasoning from moral principles) to make moral judgments. As evidence of this, they have shown that the footbridge problem causes activation in areas of the brain associated with emotion, while the trolley problem activates cognitive areas. It appears that the negative emotions associated with pushing someone off a bridge override the moral principles that demand we save the five people.

In Greene’s studies, the negative emotions people experience are elicited by the moral dilemmas themselves, but what would happen if we were experiencing emotions that were unrelated to the dilemmas as we encountered them. Could these emotions influence how we make moral judgments? For example, if we were experiencing positive emotions when we encountered a potential personal moral violation, could those irrelevant emotions override the negative emotions caused by the personal violation, and causes us to use more principle-based cognitive processes in making a judgment?

In a study published in the June issue of Psychological Science, Piercarlo Valdesolo and David DeSterno3 sought to answer this question by inducing positive emotions in participants, and presenting them with the trolley and footbridge problems. Before being presented with the problems, half of their participants watched a 5-minute Saturday Night Live clip (I assume it was an old clip, so that it would actually be funny), intended to induce positive emotions, while the other half watched a “neutral” 5-minute clip of a documentary on a Spanish village. All participants were then presented with both problems, in random order.

Recall that in most cases, participants presented with these two problems answer that it is OK to turn the trolley (impersonal violation), but not OK to push the man off the bridge (personal violation). If the SNL clip induces positive emotions, and these override the negative emotions caused by personal violations, then participants who viewed that clip should be more likely to reason using utilitarian considerations when they read the footbridge problem, and thus say that it is morally permissible to push the man off the bridge to stop the train. This is in fact what they found. Twenty-five percent of the participants who viewed the SNL clip said that it was permissible to push the man off the bridge, while only 8% of the participants who viewed the neutral clip said it was permissible. As expected, the clips did not affect the judgments made in the trolley problem. So, emotions elicited by stimuli unrelated to a moral dilemma can influence judgments we make about that dilemma.

I have to admit that I find this a bit disturbing. It seems that when we encounter a moral problem, we’re unable to distinguish the emotions that are elicited by the problem, and those that are a result of other properties of the context in which we encounter the moral problem. One can imagine situations in which this actually helps us to make moral judgments, as was the case in this study. If using more cognitive, “rational” processes is better than using emotion-driven processes, then the experiment shows that contexts that induce positive emotions can actually cause us to make better moral judgments. However, the potential for manipulation is great. One can imagine politicians, for example, presenting moral problems (e.g., abortion) in contexts designed to induce positive or negative emotions unrelated to those problems, in order to influence the moral judgments people make (and, in turn, how they vote). And I suspect that as we learn more about the roles played by emotion in moral judgment, disturbing findings like this one will become more common.

¹Greene, J.D., Sommerville, R.B., Nystrom, L.E., Darley, J.M., & Cohen, J.D. (2001). An fMRI investigation of emotional engagement in morajudgmentnt. Science, 293, 2105-2108.
²Greene, J.&d Haidt, J. (2002) How (and where) does moral judgment work? Trends in Cognitive Sciences, 6(12), 517-523.
³Piercarlo, V., & DeSterno, D. (2006). Manipulations of emotional context shape moral judgments. Psychological Science, 17(6), 476-477.