Summary: The same brain defense circuitry that helps us avoid danger is also engaged when people act selflessly to help others at risk.
Source: Karolinska Institutet
How do people decide to intervene when someone else is in danger? Researchers at Karolinska Institutet in Sweden report that the brain systems used to detect and avoid threats are also activated when individuals choose to help others, even at personal risk.
The study’s results were published in the journal eLife.
“Our results suggest that the brain’s defensive circuitry contributes more to helping behavior than has been appreciated,” says Andreas Olsson, professor in the Department of Clinical Neuroscience at Karolinska Institutet and the study’s senior author. “These findings challenge the assumption that suppressing one’s own fear systems is necessary to assist someone in danger.”
Historically, empathy for another person’s distress has been viewed as the primary motivator for helping. But when we consider helping someone facing danger, we must also weigh the potential cost or hazard to ourselves—such as entering a burning building or reaching onto train tracks to rescue a stranger. The researchers set out to examine how neural circuits for defense and self-preservation influence decisions to help others under threat.
Imaging brain responses during risky helping decisions
Previous animal studies suggested defensive systems play a role in protective behavior toward others, but human evidence has been limited. To address this, the research team recruited 49 healthy volunteers and used functional magnetic resonance imaging (fMRI) while participants made choices about helping an unfamiliar person avoid mild electric shocks.
Participants viewed the other person on a screen and were informed whether, by choosing to help, they might themselves receive a shock. The task also varied how imminent the threat was; participants were told how soon a potential shock would occur so that the researchers could assess neural and behavioral responses as threat proximity changed.
Amygdala and other defensive regions shape helping choices
The study found that regions traditionally linked to rapid defensive responses were engaged when participants decided whether to help. In particular, activity in the amygdala—an evolutionarily ancient structure involved in threat detection and basic defense behaviors—was associated with participants’ willingness to help the other person.
Beyond the amygdala, increased engagement of regions such as the insula, periaqueductal gray (PAG), and anterior cingulate cortex (ACC)—areas that coordinate fast defensive actions—was linked to a greater likelihood of helping. Notably, the brain signals that best predicted helping reflected representations of the perceived threat itself, rather than the other person’s distress.
Using representational similarity analysis, the researchers showed that the extent to which the amygdala and insula encoded threat-related information about the situation (and not merely the victim’s distress) predicted participants’ decisions to intervene. In contrast, brain areas typically involved in higher-order cognitive processing did not reliably predict helping when the danger was imminent.
These findings indicate that, in humans as in other mammals, defensive neural mechanisms can facilitate prosocial actions when another individual is threatened. The results expand our understanding of the neural basis of helping by highlighting how self-oriented defense systems and social motives interact during risky decisions to assist others.
Future directions
The team plans to investigate how the presence of additional bystanders influences helping behavior and how observers learn from such events. They are especially interested in how fear, social learning, and moral judgments about right and wrong are transmitted between people through experience and observation.
Funding: The research was supported by the Swedish Research Council and the Knut and Alice Wallenberg Foundation (Wallenberg Academy Fellow grant to Andreas Olsson). The authors declare no competing interests.
About this neuroscience research news
Author: Press Office
Source: Karolinska Institutet
Contact: Press Office – Karolinska Institutet
Image: The image is in the public domain
Original research: Open access. Title: “Neural defensive circuits underlie helping under threat in humans” by Andreas Olsson et al., published in eLife.
Abstract
Neural defensive circuits underlie helping under threat in humans
Empathy for others’ distress has long been viewed as the main driver of helping behavior. Yet helping someone in danger also requires assessing risk to oneself. While research on animals has implicated defensive responses in protective acts toward conspecifics, the role of human defensive circuitry in helping has been understudied.
In this pre-registered study with 49 participants, volunteers underwent fMRI scanning while deciding whether to help another person avoid aversive electrical shocks at the potential cost of also receiving shocks. We observed that greater recruitment of neural circuits that coordinate rapid defensive actions—including the insula, PAG, and ACC—was associated with increased decisions to help.
Crucially, representational analyses revealed that the degree to which the amygdala and insula specifically encoded the perceived threat (rather than the other person’s distress) predicted helping behavior. These findings suggest that human defensive mechanisms play an important role in prosocial decisions under danger, complementing empathic motivations and expanding our understanding of the neural basis for selfless acts.