Greene et al, 2004 wrote:IntroductionFor decades, moral psychology was dominated by developmental theories that emphasized the role of reasoning and “higher cognition” in the moral judgment of mature adults (Kohlberg, 1969). A more recent trend emphasizes the role of intuitive and emotional processes in human decision making (Damasio, 1994) and sociality (Bargh and Chartrand 1999, Devine 1989), a shift in perspective that has profoundly influenced recent work in moral psychology (Haidt 2001, Rozin et al. 1999). Our previous work suggests a synthesis of these two perspectives (Greene and Haidt 2002, Greene et al. 2001). We have argued that some moral judgments, which we call “personal,” are driven largely by social-emotional responses while other moral judgments, which we call “impersonal,” are driven less by social-emotional responses and more by “cognitive” processes. (As discussed below, the term “cognitive” has two distinct uses, referring in some cases to information processing in general while at other times referring to a class of processes that contrast with affective or emotional processes. Here we use quotation marks to indicate the latter usage.)
Personal moral dilemmas and judgments concern the appropriateness of personal moral violations, and we consider a moral violation to be personal if it meets three criteria: First, the violation must be likely to cause serious bodily harm. Second, this harm must befall a particular person or set of persons. Third, the harm must not result from the deflection of an existing threat onto a different party. One can think of these three criteria in terms of “ME HURT YOU.” The “HURT” criterion picks out the most primitive kinds of harmful violations (e.g., assault rather than insider trading) while the “YOU” criterion ensures that the victim be vividly represented as an individual. Finally, the “ME” condition captures a notion of “agency,” requiring that the action spring in a direct way from the agent's will, that it be “authored” rather than merely “edited” by the agent. Dilemmas that fail to meet these three criteria are classified as “impersonal.” As noted previously (Greene et al., 2001), these three criteria reflect a provisional attempt to capture what we suppose is a natural distinction in moral psychology and will likely be revised in light of future research.
An example of an impersonal moral dilemma is the
trolley dilemma (Thomson, 1986): A runaway trolley is headed for five people who will be killed if it proceeds on its present course. The only way to save them is to hit a switch that will turn the trolley onto an alternate set of tracks where it will kill one person instead of five. Should you turn the trolley in order to save five people at the expense of one? Most people say yes (Greene et al., 2001). An example of a personal moral dilemma is the
footbridge dilemma (Thomson, 1986): As before, a trolley threatens to kill five people. You are standing next to a large stranger on a footbridge spanning the tracks, in-between the oncoming trolley and the hapless five. This time, the only way to save them is to push this stranger off the bridge and onto the tracks below. He will die if you do this, but his body will stop the trolley from reaching the others. Should you save the five others by pushing this stranger to his death? Most people say no (Greene et al., 2001). The trolley dilemma, unlike the footbridge dilemma, is impersonal because it involves the deflection of an existing threat (i.e., no agency—it is “editing” rather than “authoring”).
The rationale for distinguishing between personal and impersonal moral violations/judgments is in part evolutionary. Evidence from observations of great apes suggests that our common ancestors lived intensely social lives guided by emotions such as empathy, anger, gratitude, jealousy, joy, love, and a sense of fairness (de Waal, 1996), and all of this in the apparent absence of moral reasoning. (By “reasoning” we refer to relatively slow and deliberative processes involving abstraction and at least some introspectively accessible components [Haidt, 2001].). Thus, from an evolutionary point of view, it would be strange if human behavior were not driven in part by domain-specific social-emotional dispositions. At the same time, however, humans appear to possess a domain-general capacity for sophisticated abstract reasoning, and it would be surprising as well if this capacity played no role in human moral judgment. Thus, we sought evidence in support of the hypothesis that moral judgment in response to violations familiar to our primate ancestors (personal violations) are driven by social-emotional responses while moral judgment in response to distinctively human (impersonal) moral violation is (or can be) more “cognitive.”
Our previous results supported this hypothesis in two ways (Greene and Haidt 2002, Greene et al. 2001). First, we found that brain areas associated with emotion and social cognition (medial prefrontal cortex, posterior cingulate/precuneus, and superior temporal sulcus/temperoparietal junction) exhibited increased activity while participants considered personal moral dilemmas, while “cognitive” brain areas associated with abstract reasoning and problem solving exhibited increased activity while participants considered impersonal moral dilemmas.
Second, we found that reaction times (RTs) were, on average, considerably longer for trials in which participants judged personal moral violations to be appropriate, as compared to trials in which participants judged personal moral violations to be inappropriate. No comparable effect was observed for impersonal moral judgment. We compare this effect on RT to the Stroop effect (MacLeod 1991, Stroop 1935), in which people are slow to name the color of the ink in which an incongruent word appears (e.g., “red” written in green ink). According to our theory, personal moral violations elicit prepotent, negative social-emotional responses that drive people to deem such actions inappropriate. Therefore, in order to judge a personal moral violation to be appropriate one must overcome a prepotent response, just as one faced with the color-naming Stroop task must overcome the temptation to read the word “red” when it is written in green ink. The sort of mental discipline required by the Stroop task is known as “cognitive control,” the ability to guide attention, thought, and action in accordance with goals or intentions, particularly in the face of competing behavioral pressures (Cohen et al. 1990, Posner and Snyder 1975, Shiffrin and Schneider 1977). We interpreted the behavioral results of our previous study as evidence that when participants responded in a utilitarian manner (judging personal moral violations to be acceptable when they serve a greater good) such responses not only reflected the involvement of abstract reasoning but also the engagement of cognitive control in order to overcome prepotent social-emotional responses elicited by these dilemmas.
Our present aim was to further test our theory of moral judgment by directly testing two specific hypotheses derived from the arguments above. First, we tested the hypothesis that increased RT in response to personal moral dilemmas results from the conflict associated with competition between a strong prepotent response and a response supported by abstract reasoning and the application of cognitive control. In keeping with this hypothesis, we predicted that the anterior cingulate cortex (ACC), a brain region associated with cognitive conflict in the Stroop and other tasks (Botvinick et al., 2001), would exhibit increased activity during personal moral judgment for trials in which the participant takes a long time to respond (high-RT trials), as compared to trials in which the participant responds quickly (low-RT), reflecting presumed conflict in processing. Likewise, we predicted that regions in the dorsolateral prefrontal cortex (DLPFC) would also exhibit increased activity for high-RT trials (as compared to low-RT trials), reflecting the engagement of abstract reasoning processes and cognitive control (Miller and Cohen, 2001).
Second, we tested the hypothesis that, in the dilemmas under consideration, these control processes work against the social-emotional responses described above and in favor of utilitarian judgments, i.e., judgments that maximize aggregate welfare (e.g., by sacrificing one life in order to save five others). In keeping with this hypothesis, we predicted increased DLPFC activity for trials in which participants judged personal moral violations to be appropriate, as compared to trials in which participants judged personal moral violations to be inappropriate. In other words, this hypothesis predicted that the level of activity in regions of DLPFC would correlate positively with utilitarian moral judgment. We emphasize that this prediction goes beyond those explored in our previous work. Previously, we found that different classes of moral dilemma (personal versus impersonal) produce different patterns of neural activity in the brains of moral decision makers. Here we test the hypothesis that different patterns of neural activity in response to the same class of moral dilemma are correlated with differences in moral decision-making behavior.
To test the predictions of this theory, we focused on a class of dilemmas that bring “cognitive” and emotional factors into more balanced tension than those featured in our previous work. For example, consider the following moral dilemma (the crying baby dilemma).
Enemy soldiers have taken over your village. They have orders to kill all remaining civilians. You and some of your townspeople have sought refuge in the cellar of a large house. Outside, you hear the voices of soldiers who have come to search the house for valuables.
Your baby begins to cry loudly. You cover his mouth to block the sound. If you remove your hand from his mouth, his crying will summon the attention of the soldiers who will kill you, your child, and the others hiding out in the cellar. To save yourself and the others, you must smother your child to death.
Is it appropriate for you to smother your child in order to save yourself and the other townspeople?
This is a difficult personal moral dilemma. In response to this dilemma, participants tend to answer slowly, and they exhibit no consensus in their judgments. This dilemma, like the other consistently difficult dilemmas used here, has a specific structure: in order to maximize aggregate welfare (in this case, save the most lives), one must commit a personal moral violation (in this case, smother the baby). According to our theory, this dilemma is difficult because the negative social-emotional response associated with the thought of killing one's own child competes with a more abstract, “cognitive” understanding that, in terms of lives saved/lost, one has nothing to lose (relative to the alternative) and much to gain by carrying out this horrific act. We believe that the ACC responds to this conflict and that control-related processes in the DLPFC tend to favor the aforementioned “cognitive” response. We hypothesize that these control processes, insofar as they are effective, drive the individual to the utilitarian conclusion that it is appropriate to smother the baby in order to save more lives.
This case contrasts with “easy” personal moral dilemmas, ones that receive relatively rapid and uniform judgments (at least from the subjects within our sample). One such case is the
infanticide dilemma in which a teenage mother must decide whether or not to kill her unwanted newborn infant. According to our theory, this dilemma is relatively easy because the negative social-emotional response associated with the thought of someone killing her own child dominates the weak or nonexistent “cognitive” case in favor of this action. Here there is no significant cognitive conflict and no need for extended reasoning or cognitive control. Thus, compared to the high-RT trials typically generated by cases like
crying baby, the low-RT trials typically generated by cases such as
infanticide should exhibit lower levels of activity in the ACC and DLPFC.
The analyses required to test these assertions make up a nested structure (Figure 1). Previously, we compared the neural activity associated with “personal” and “impersonal” moral judgments (Greene et al., 2001). In analysis 1, we tested our hypotheses concerning conflict monitoring in the ACC and abstract reasoning and cognitive control in the DLPFC by comparing high-RT to low-RT personal moral judgments. In analysis 2, we tested our hypothesis concerning the involvement of DLPFC in “cognitive” processes underlying utilitarian judgments by subdividing the high-RT personal moral judgments according to the participant's behavior, i.e., by comparing “utilitarian” judgments (“appropriate”) to nonutilitarian judgments (“inappropriate”). In each of these difficult dilemmas, an action that normally would be judged immoral (e.g., smothering a baby) is favored by strong utilitarian considerations (e.g., saving many lives). The participants, in each instance, must decide if the utilitarian action is “appropriate” or “inappropriate.” Our hypothesis is that judgments of “appropriate” will be associated with greater DLPFC activity than those of “inappropriate,” reflecting the influence of “cognitive” processes favoring a utilitarian response. Analysis 2 was performed only on high-RT trials because of the relative paucity of low-RT-utilitarian judgments and the need to control for RT.
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