In a new study, neuroscientists have delved deeper into how the human brain approaches moral judgment. Their findings reveal that our moral decisions activate various distinct areas of the brain, challenging the idea that morality is processed in a single “moral hot spot.” The study, published in Human behavioralso uncovered intriguing variations in moral perception based on political ideology.
The motivation behind this study lies in one of the most heated debates in moral science: whether our moral reasoning is a monolithic or diverse process. At the heart of this debate is moral foundations theory, which argues in favor of the latter. According to this theory, our moral compass is guided not by a single north star but by multiple, contextually varying moral intuitions.
These foundations include care, fairness, loyalty, authority, sacredness, and, more recently, freedom. Essentially, this theory suggests that our moral judgments arise from different mental processes, evolved to address specific social challenges. Researchers have sought to determine whether our moral judgments about different domains such as care, fairness or loyalty are processed in distinct neural systems or whether they converge into a unified framework.
“Complex, context-dependent moral judgment is a uniquely human capacity and is central to most human-to-human social interactions, either directly person-to-person or mediated. As such, this is an important and fascinating topic for a cognitive psychologist, neuroscientist and communications scientist to study,” said study author René Weber, a professor at the University of California in Santa Barbara and director of the Media Neuroscience Lab at UCSB.
To explore this, researchers conducted an experiment involving 64 participants, primarily young adults from the University of California, Santa Barbara community. Participants underwent functional magnetic resonance imaging (fMRI), a technology that visualizes brain activity by detecting changes associated with blood flow.
During the scans, participants engaged in a task involving moral foundation vignettes – brief descriptions of actions that violated specific moral foundations. The vignettes also included transgressions of non-moral social norms, such as eating cereal with water instead of milk, which served as a control. Participants rated these actions based on their perception of moral injustice. This setup allowed the researchers to observe which parts of the brain were activated during different moral judgments.
As expected, moral violations (physical care, emotional care, fairness, freedom, authority, loyalty, and sanctity) were judged to be more morally wrong than transgressions of social norms. Judging moral transgressions also took longer on average than judging social norm transgressions, suggesting a deeper cognitive process involved in evaluating moral actions.
Researchers found that different areas of the brain were activated for moral violations versus transgressions of social norms. A distributed network involving areas such as the dorsomedial prefrontal cortex, posterior cingulate cortex, temporoparietal junction, and primary visual cortex showed common activation across moral foundations. This suggests that these areas of the brain play a critical role in distinguishing between moral judgments and transgressions of non-moral social norms.
By examining how specific moral foundations were processed in the brain, researchers found that each of these moral categories caused unique patterns of brain activity. This finding is particularly significant because it aligns with moral foundations theory, which posits that different moral considerations are rooted in distinct cognitive processes.
An important achievement of the study was the development of a decoding model capable of predicting which specific moral foundation or social norm an individual was judging, based on patterns of activity in their brain. This level of prediction would not be achievable if all moral categories were processed uniformly at the neurological level.
“Our results indicated that there are very specific neural signatures of different dimensions or moral foundations,” Weber told PsyPost. “These signatures can even be used to decode moral judgment, that is, to predict the moral judgment of individuals based on their brain activation pattern. The precision with which this can be done surprised us. We are currently testing moral decoding on different datasets and problems and trying to reproduce our results in our Human behavior article.”
The researchers also found that liberals and conservatives showed distinct patterns of brain activation when making moral judgments. This suggests that an individual’s political orientation is not only a reflection of their social and moral beliefs, but also influences the fundamental neural processes that underlie these beliefs.
Liberals showed more pronounced neural responses to moral transgressions related to care/harm and fairness/cheating. These foundations generally protect the rights and freedoms of individuals. Liberals’ heightened sensitivity to these moral dimensions was reflected in their brains’ specific activation patterns.
On the other hand, conservatives demonstrated greater neural engagement when addressing moral issues related to loyalty/betrayal, authority/subversion, and sanctity/degradation. These categories generally operate at the group level, emphasizing group cohesion, respect for authority, and purity. Brain scans of conservatives have shown that they are neurologically more sensitive to these aspects of moral reasoning.
For example, when judging individualizing versus constraining moral foundations, the lingual gyrus, visual cortex, anterior prefrontal cortex, and superior temporal cortex showed significant differences in activity between liberals and conservatives. These areas are associated with various cognitive functions, including semantic processing and intention attribution, suggesting that ideological differences might affect fundamental cognitive processing during moral judgments.
Together, the results challenge the idea of a singular “moral hot spot” in the brain. Rather, it suggests that our moral judgments are the result of a more distributed neural process.
“Morality or moral judgment is not just ‘one thing’ or does not arise from a single concern (e.g., harming or caring for others),” Weber told PsyPost. “At its core, the function of morality is to facilitate (group) cohesion and cooperation among humans. Because there are many cooperative problems to solve, moral judgment is diverse and different individuals develop different moral sensibilities.
“In many ways, I think our results clarify that monism and pluralism are not necessarily mutually exclusive approaches,” added first author Frederic Hopp, who led the study as a doctoral student in the Media Neuroscience Lab . “We show that moral judgments about a wide range of different types of morally relevant behaviors are instantiated in shared brain regions.”
Despite these significant results, the study has its limitations. On the one hand, the sample size and demographics (primarily college-affiliated young adults) might not represent the entire spectrum of moral cognition across different ages, cultures, and backgrounds. Additionally, although fMRI is a powerful tool, it has limitations in identifying the exact neural mechanisms at play.
Future research could focus on broadening the demographic diversity of participants or using even more advanced neuroimaging techniques. Furthermore, exploring how moral decision-making develops over time and in different cultural contexts could add another level of understanding to this complex facet of human cognition.
“There are dozens of additional questions to answer,” Weber said. “The question of why and how moral judgment works has been an important topic for researchers of diverse backgrounds for millennia, and it will occupy them for a long time to come. For us, our next goals are to test different theories of moral judgment against each other and to replicate our findings in our Human behavior article in more diverse populations.
The study, “Moral Foundations Elicit Shared and Dissociable Cortical Activation Modulated by Political Ideology,” was authored by Frederic R. Hopp, Ori Amir, Jacob T. Fisher, Scott Grafton, Walter Sinnott-Armstrong, and René Weber .
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