Using fMRI to Dissect Moral Judgment

Overview

Source: William Brady & Jay Van Bavel—New York University

In examining the roles of reason and emotion in moral judgments, psychologists and philosophers alike point to the trolley dilemma and the footbridge dilemma. With the trolley dilemma, most people say that it is appropriate to pull a switch to stop a train from hitting five people by diverting it to kill one person. However, with the footbridge dilemma, most people say it is inappropriate to push a large man off of a bridge in order to hit a train (killing him) and stop it from running into five people. Reason would dictate that in both of the foregoing dilemmas, one life should be sacrificed to save five lives. But to many people, pushing the large man just “feels wrong” because it triggers more negative emotions than pulling a switch. In this case, emotion seems to trump reason.

In recent years, psychology and neuroscience have entered the debate over the roles of reason and emotion in moral judgment. Researchers can scan brain activity as individuals make making moral judgments. Research shows that different brain areas associated are active during contemplation of the footbridge dilemma versus the trolley dilemma.

Inspired by Greene, Sommerville, Nystrom, Darley and Cohen, this video demonstrates how to design moral dilemma tasks and integrate them into experiments using using functional magnetic resonance imaging (fMRI) technology.¹

Procedure

1. Data Collection

Conduct a power analysis and recruit a sufficient number of participants.
Create 30 moral dilemmas divided equally into categories of (1) personal moral dilemmas, (2) impersonal moral dilemmas, and (3) non-moral dilemmas. See the supplementary materials from Greene et al. for specific examples.¹
1. A personal moral dilemma involves the participant imagining to perform an action that directly harms one person in the service of some goal

Results

The imaging data support the idea that emotion is more involved in personal moral dilemmas than impersonal dilemmas and non-moral dilemmas (Figure 1). Brain areas previously linked with emotion (e.g., the medial frontal gyrus) were significantly more active when participants made judgments about personal dilemmas (e.g., the footbridge dilemma) than when they made judgments about impersonal dilemmas (e.g., the trolley dilemma). For impersonal dilemmas, brain areas previously lin

Application and Summary

In the debate over the effects of reason versus emotion in moral judgment, this experiment provides evidence of powerful psychological processes involved: Moral judgments about personal dilemmas rely heavily on emotional processes, while moral judgments about impersonal dilemmas rely more heavily on reasoning processes. Indeed, judgments concerning impersonal dilemmas are more like judgments concerning non-moral dilemmas than personal dilemmas. Techniques involved in this experiment are basic, and the results deriv

References

Greene, J. D., Sommerville, R. B., Nystrom, L. E., Darley, J. M., & Cohen, J. D. (2001). An fMRI investigation of emotional engagement in moral judgment. Science, 293 (5537), 2105-2108.
Weston, D. (2007). The political brain: The role of emotion in deciding the fate of nations. Perseus Books.
Bartels, D. M. & Pizarro, D. A. (2011). The mismeasure of morals: Antisocial personality traits predict utilitarian responses to moral dilemmas. Cognition, 121, 154-161.