Early national data suggest that 2025 recorded fewer mass killings than recent peak years, continuing a broader post-pandemic decline in lethal violence. The number of homicides nationwide is projected to be the lowest since the FBI began tracking such data in 1960. While any loss of life remains unacceptable, this downward shift raises an important psychological question: What changed?

The answer is unlikely to be found in a single policy, personality type, or diagnostic category. Instead, the data invite us to view violence through the lens increasingly used in neuroscience and evolutionary biology—not as a switch that suddenly turns on, but as a threshold-dependent behavior.

Violence Is Not Binary—It Is Gated

A useful way to think about extreme violence is through a simple behavioral grammar:

Behavior = Archetype × Drive × Culture × Threshold

Often referred to as the ARCH model, this equation reflects a core insight from ethology, psychiatry, and systems neuroscience: no single factor causes violence. Violence emerges only when multiple necessary conditions converge and a threshold is crossed.

• Archetype refers to conserved neural scripts—defense, dominance, revenge, sacrifice—that evolved long before modern society.
• Drive is the motivational energy powering action: fear, rage, humiliation, or the need for recognition.
• Culture supplies meaning, justification, and symbolic framing.
• Threshold determines whether latent impulses ever become behavior.

If any one component is absent, the behavior collapses. Strong grievance without cultural permission rarely leads to mass violence. Cultural hostility without energized individuals rarely produces attackers. Most crucially, high thresholds prevent action even when other elements are present.

Importantly, approaching the threshold does not mean a person will inevitably cross it. Many individuals experience intense grievance, anger, or despair without acting violently because at least one regulatory brake remains intact. Cultural inhibition, internalized moral limits, fear of harming innocents, or the realization that violence would permanently define one’s identity can keep the threshold from being crossed. In other cases, access to non-violent routes for recognition or relief—being heard, receiving validation, engaging in meaningful work, or simply having the moment interrupted by sleep, human contact, or clinical intervention—can dissipate the surge of motivational drive. From a threshold perspective, prevention does not require eliminating pain or conflict; it requires ensuring that at least one gate—cultural, psychological, or physiological—remains closed long enough for the moment to pass.

Culture as a Threshold Regulator

Culture does not invent aggression. Humans—and many other social mammals—already possess neural systems for threat detection, status competition, and coalition defense. What culture does is raise or lower the threshold for using those systems.

History offers sobering examples. In Nazi Germany, the population did not suddenly become biologically violent. Instead, sustained propaganda reframed violence as morally justified, socially rewarded, bureaucratically normalized, and psychologically sanctioned. The threshold for harming Jews was progressively lowered, while thresholds for dissent, empathy, and restraint were raised. The same nervous systems, operating under a different cultural field, produced radically different behavior.

This pattern is not unique to totalitarian regimes. Whenever violence is framed as honorable, redemptive, or identity-affirming, thresholds fall. When violence is framed as shameful, futile, or socially invisible, thresholds rise.

What May Have Shifted in 2025

The decline in mass killings in 2025 does not mean grievance disappeared, firearms vanished, or mental illness resolved. Instead, it suggests fewer individuals crossed the behavioral threshold.

Several cultural factors may contribute:

• Reduced symbolic payoff: Less sensational coverage and fewer narratives that immortalize attackers reduce incentives for notoriety-seeking violence.
• Threshold fatigue: After years of saturation, public appetite for endlessly circulating mass violence may have diminished.
• Shifts in grievance framing: While social conflict persists, fewer narratives may be translating personal grievance into moralized violence.
• Disruption of imitation loops: Copycat dynamics rely on repeated symbolic rehearsal; when imitation weakens, thresholds rise.

None of these factors eliminates risk. But together, they alter the probability landscape.

At the same time, contemporary cultural narratives surrounding diversity, equity, and inclusion (DEI) and transgender rights have become prominent fault lines in public discourse. Right-leaning narratives often frame these issues as threats to tradition or social cohesion, while left-leaning narratives emphasize the protection of marginalized identities and inclusive norms. When such narratives harden into binary moral frames, they can unintentionally intensify polarization rather than reduce it.

What Chimpanzees Can Teach Us

Research on chimpanzees offers a useful evolutionary parallel. Male chimps engage in coalitionary killings—but only under specific conditions: numerical advantage, low personal risk, group sanction, and territorial justification. When those conditions are absent, even aggressive individuals do not attack. The behavior is threshold-gated, not impulsive.

Humans share this architecture, with a critical difference: symbols replace proximity. A flag, ideology, grievance narrative, or media script can function like a territorial boundary—if culture lowers the threshold.

Prevention Means Raising Thresholds

If violence were caused solely by individual pathology, prevention would be clinical. If it were caused solely by ideology, prevention would be political.

But if violence is threshold-regulated, prevention is also cultural.

Raising thresholds means removing symbolic rewards for violence, disrupting imitation and legacy narratives, restoring norms that frame violence as failure rather than meaning, and offering non-violent routes to status, dignity, and recognition.

Cultures that succeed in reducing mass violence do not eliminate aggression. They make it harder for aggression to execute.

The Takeaway

Efforts to promote inclusion—such as DEI initiatives and recognition of transgender rights—aim to broaden belonging and equity. Yet when experienced as zero-sum or communicated without shared frameworks, they can unintentionally foster backlash and reinforce us-versus-them dynamics across both right- and left-leaning groups. Inclusive cultures function best when they affirm shared dignity rather than competing identities.

2025’s lower number of mass killings does not signal safety—but it does reveal something important: violence is not inevitable. It depends on whether ancient neural scripts are permitted to cross modern cultural thresholds.

References

Rahman, Tahir, Charles F. Zorumski, and J. Reid Meloy. "The ARCH model: a neuroevolutionary framework for behavioral execution." Frontiers in Psychiatry 16 (2025): 1669530.

Rahman, Tahir, and Charles Zorumski. "Sterol-Modulated Thresholds as an Evolutionary Framework for Biological Execution." Available at SSRN 6017079.

Rahman, Tahir, Sarah M. Hartz, Willa Xiong, J. Reid Meloy, Jeffrey Janofsky, Bruce Harry, and Phillip J. Resnick. "Extreme overvalued beliefs." Journal of the American Academy of Psychiatry and the Law 48, no. 3 (2020): 319-326.

Rahman, Tahir, and J. Reid Meloy. "Archetype killers." Journal of Threat Assessment and Management (2025).

Chan, Wing Yi, Mary Ann Hollingsworth, Dorothy L. Espelage, and Kimberly J. Mitchell. "Preventing violence in context: The importance of culture for implementing systemic change." Psychology of violence 6, no. 1 (2016): 22.

Jagdeep, Ankita, Anisha Jagdeep, Simon Lazarus, Mendel Zecher, Ohad Fedida, Gidon Fihrer, Collin Vasko et al. "Instructing animosity: How DEI pedagogy produces the hostile attribution bias." Rutgers University’s Social Perception Lab: Network Contagion Research Institute (NCRI) (2024): 1-23.