Almost everything you thought you knew about psychopathy has long been overturned. So why does this thoroughly debunked notion still persist?
The Origins of Psychopathy and Public Perception
Psychopathic personality disorder—commonly known as psychopathy—is one of the oldest and most extensively researched diagnostic labels in mental health. The earliest known reference dates back to 1786, in a short essay by American physician Benjamin Rush. He described a peculiar condition he termed "anomia," later renamed "moral derangement," wherein patients supposedly lost the ability to distinguish right from wrong. Though highly speculative, this idea laid the groundwork for the scientific concept of the "psychopath": an individual suffering from an extreme physiological impairment that undermines innate moral cognition and prosocial behavior.
In modern scientific discourse, psychopaths are typically defined by a cluster of specific symptoms: lack of empathy, absence of conscience, and no remorse; accompanied by predatory violence, pathological lying, and uncontrolled impulsivity. Prominent psychopathy researcher Robert Hare described them thus in his 1993 book Without Conscience:
"Psychopaths are social predators. They charm, manipulate, and recklessly plow their way through life, leaving behind a trail of broken hearts, shattered expectations, and empty wallets. With no conscience and no feeling for others, they selfishly take what they want and do as they please, violating social and moral norms without a shred of guilt or regret."
Psychopaths have also become iconic figures in popular culture, frequently appearing in bestsellers and suspense thrillers. One of the most representative characters is Anton Chigurh, portrayed by Javier Bardem in the 2007 film No Country for Old Men. Emotionless and relentless, he murders innocents on the desolate Texas plains as if slaughtering livestock. While such characters are fictional exaggerations rather than accurate clinical portrayals, they encapsulate the public's core impression of psychopathy: emotional coldness and moral void.
▷ Scene from No Country for Old Men
The Empirical Collapse of Core Psychopathy Claims
Yet this entire framework surrounding psychopathy suffers from a fatal flaw.
Since the late 1990s, when research on psychopathy exploded, hundreds of empirical studies have been conducted. Virtually none have produced reliable evidence supporting the widely circulated conclusions. While some studies in the 1990s and early 2000s appeared to validate psychopathy theories—sparking temporary excitement among scholars—the findings of the past two decades have been sobering: nearly every claim about psychopathy has either been thoroughly refuted or fails to receive empirical support in experiments.
Psychopathy, perhaps, simply does not exist.
Consider one of the most common assertions: that psychopaths cannot empathize or understand others' emotions. This view directly contradicts current scientific findings. In empathy experiments, individuals diagnosed as psychopathic perform almost identically to non-psychopathic controls.
The most compelling evidence comes from a recent systematic review on empathy conducted by our team (Rasmus Rosenberg Larsen et al.). This review incorporated 66 studies involving 5,711 clinically assessed psychopathic participants. Results showed that in 89.11% of experiments, statistical analysis could not distinguish empathy performance between psychopathic and non-psychopathic groups. In higher-quality studies employing more rigorous statistical methods, this "no difference" rate soared to 94.77%. In behavioral science, such consistently negative results nearly prove that individuals diagnosed as psychopathic do not suffer from empathy deficits.
▷ Larsen, Rasmus Rosenberg, et al. "Do psychopathic persons lack empathy? An exploratory systematic review of empathy assessment and emotion recognition studies in psychopathy checklist samples." Psychology, Public Policy, and Law (2024).
Another pervasive belief is that psychopaths lack emotions entirely—a notion dating back to the concept's origins and popularized by psychiatrist Hervey Cleckley in his 1941 book The Mask of Sanity. Cleckley proposed that psychopathy is fundamentally a neurological disorder of the emotional system, resulting in abnormally shallow affect. He argued that while psychopaths can mimic normal emotions, beneath this facade lies an emotional wasteland. The character Chigurh mentioned earlier largely embodies this description.
In reality, in the vast majority of relevant tests, researchers have failed to find clear differences between psychopathic individuals and control groups.
Most researchers have long abandoned this view. Today, it is considered baseless, with no concrete evidence ever substantiating it. Although clinically diagnosed psychopaths may appear emotionally flat on the surface, detailed analyses using physiological measures of emotional response—such as skin conductance, heart rate, and brain activity—reveal a different truth.
Early studies, such as David Lykken's 1957 experiment using skin conductance to measure emotional responses, were misinterpreted as evidence of shallow emotions in psychopaths. Similar studies emerged in the 1990s, notably a widely cited 1993 paper by Christopher Patrick and colleagues, which seemed to reaffirm this view.
However, close examination reveals these studies' methods and results are extremely weak and untenable. Since 1980, at least 27 studies using standard psychophysiological techniques have directly tested the emotional response systems of diagnosed psychopaths. None have proven any deep-seated functional impairment. In the overwhelming majority of these tests, no clear distinction could be made between psychopathic individuals and control groups. Essentially, this represents an accumulation of non-significant findings. Due to the consistent failure to证实 the "shallow emotions" hypothesis, researchers have nearly ceased testing it: only one related psychophysiological study has been published in the past decade.
Nearly all claims about psychopathy follow the same trajectory: initial studies provide preliminary support for a common assertion, but within years, numerous subsequent studies either fail to replicate the early results or directly refute them. This pattern holds true for other assertions, including that "psychopaths are extremely dangerous," "psychopaths are impulsively out of control," "psychopaths are immune to cognitive behavioral therapy," "psychopathy has genetic biomarkers," or "psychopathy stems from structural and functional brain abnormalities." Whatever you've heard about psychopathy, rigorous researchers will coldly inform you: it's merely untenable speculation.
Why have experimental psychologists struggled so persistently to validate the concept of the "psychopath"?
Before answering, we must acknowledge the current situation is deeply puzzling. In the early 2000s, psychopathy research was regarded as one of the most cutting-edge and robust paradigms in clinical and forensic psychology. Today, the field is increasingly defined by "exaggerated claims" and "unverified assumptions." More notably, throughout history, psychopathy has been portrayed as a severe affliction accompanied by extreme psychological traits. If psychopaths truly possessed these extreme traits, experimental psychologists should theoretically be able to measure and record them relatively easily. The fact that they consistently cannot is, frankly, anomalous.
Although more researchers are beginning to explore the reasons for this impasse, no clear consensus has yet emerged in academia. However, two explanations have been thoroughly discussed within scholarly circles.
The first, and perhaps most common, explanation is that, like other personality disorders, psychopathy is simply too difficult to study with existing tools and techniques. Psychopathy might indeed be a personality disorder linked to extreme traits (such as lack of empathy or shallow emotions), but our scientific instruments aren't yet precise enough to reliably capture these traits. This methodological limitation faced by scientists studying personality disorders is reflected in the available evidence.
However, it must be clarified that many studies testing psychopathy claims are far from rudimentary.
This line of reasoning is prevalent in research literature, typically appearing in the conclusion sections of papers. After accumulating yet another batch of evidence failing to support their hypotheses, researchers discuss future challenges. In these discussions, the "absence of evidence" does not prompt them to question the absurdity of the "psychopathy" concept itself; instead, it serves as a convenient shield for "technical limitations."
The problem with this viewpoint is that it mocks behavioral science, implying the discipline remains too primitive to conduct rigorous research. This is false. Over the past two decades, behavioral science has made tremendous methodological and technological advances. Many studies testing psychopathy claims have employed high-resolution neuroimaging, complex statistical models, and well-validated psychometric tools. If psychopathy truly implied extreme deficits in empathy, emotion, and impulse control, these traits should have been detected by now. The continued failure to detect them cannot be explained away by citing limitations in behavioral science.
▷ Source: The MIT Press Reader
The second related explanation for the "lack of experimental evidence for psychopathic traits" is that researchers haven't yet found the right tools to identify "true psychopaths." This argument stems from an ongoing debate: how best to define and measure psychopathy. Multiple camps exist within this debate, each claiming to possess the accurate definition and an easy-to-use measurement tool.
Proponents of this explanation often point out that the vast majority of scientific research on psychopathy uses the "Hare Psychopathy Checklist-Revised (PCL-R)" as the standard for screening study samples. The PCL-R is undoubtedly the most commonly used psychopathy assessment tool in clinical and forensic settings. They argue that if the PCL-R is flawed, then research based on samples screened by this tool amounts to making inferences about the wrong population. At first glance, this seems reasonable: misclassifying individuals in clinical research—labeling non-psychopaths as psychopaths—would naturally skew the data. However, closer scrutiny reveals serious flaws in this explanation.
While criticizing the PCL-R is entirely valid, researchers and practitioners have long regarded it as "the best available tool for identifying patient prototypes associated with the concept of psychopathy." In other words, when researchers use the PCL-R, they praise the tool for筛选 ing individuals who exhibit all the typical characteristics of psychopaths. This is precisely the core function of clinical assessment tools: to help clinicians reliably screen for patient prototypes as defined by the clinical community.
Even if alternative tools replace the PCL-R, these substitutes are still designed (more or less) to screen for individuals matching the consensus stereotype: those exhibiting all traits historically and conceptually linked to psychopathy. Therefore, expecting dramatically different results is wishful thinking. Indeed, literature confirms this: studies using alternative assessment tools for sample screening have similarly failed to validate common claims about psychopathy.
Psychopathy as a Zombie Idea in Science
Thus, the central question remains suspended: why is there virtually no empirical data supporting the concept of psychopathy?
Currently, an alternative answer receiving little attention is this: psychopathy may be what scientists call a "zombie idea"—a concept intuitively appealing but fundamentally a misunderstanding of reality. Like zombies, even after being disproven and declared dead, these ideas stubbornly persist in prestigious universities, infecting new generations of young scientists.
History offers many examples of "zombie ideas," such as phrenology, racial theories, or geocentrism. Their commonality lies in their widespread acceptance by scientists for decades even after being thoroughly refuted by scientific research. This touches the core of "zombie ideas": those infected by them strangely fail to realize the idea is dead. Thus, "zombie ideas" are often sustained by strong biases—even when confronted with obvious contradictory evidence, scientists adhering to them rarely question the idea itself. Fortunately, "zombie ideas" in science are relatively rare, but they remain a peculiar phenomenon.
Take racial theory as an example: the notion that the human species can be divided into multiple biologically distinct subtypes, or "races," such as white, black, Asian, etc. For many scientists in modern times, this once seemed like common sense about the world. However, by the mid-20th century, biologists discovered DNA and began studying population genetics. As early as 1972, Richard Lewontin's famous "allocation study" irrefutably proved racial theory completely wrong. Despite this, hundreds of biologists and anthropologists ignored overwhelming evidence and continued researching racial theories, many until the end of their academic careers.
So, is psychopathy also a "zombie idea"? Although verifying and proving a contemporary concept as a "zombie idea" is extremely difficult—perhaps only achievable through historical hindsight—at least three aspects serve as strong evidence suggesting psychopathy may indeed be one.
The vast majority, if not all, of the serial killers we know of cannot be clearly categorized as psychopaths.
First, scientists have never found compelling evidence proving the existence of "psychopaths." We have never convincingly documented a category of people whose psychological disorders cause them to lose empathy, emotion, or impulse control. Of course, in clinical settings, you might encounter a few patients who seem to perfectly fit these labels, but this is entirely different from proving they "physiologically possess such deficits."
Second, supporters of psychopathy research often base their belief in this disorder on what they perceive as "typical cases of real-world psychopathic criminals." For instance, many researchers cite notorious serial killers like Ted Bundy or John Gacy as proof of psychopathy's existence, arguing that only the concept of "psychopathy" can explain the seemingly illogical behavior of these murderers. However, this observation might itself be the strongest evidence that "psychopathy is a zombie idea": because upon closer examination of these serial killers' psychological states, the vast majority (if not all) of known serial killers cannot be clearly categorized as psychopaths.
▷ Ted Bundy during his 1978 trial. Source: Bettmann
Take Bundy as an example. Researcher J. Reid Meloy once described him as a "typical psychopath." Although Bundy is sometimes portrayed as someone who was originally normal but suddenly decided to kidnap, murder, and mutilate women without guilt or remorse, detailed studies of his life reveal he suffered from various mental health issues long-term, including delusions, violent impulses, and substance abuse. He also had a history of inferiority complex and social awkwardness—traits rarely associated with psychopathy. Moreover, as far as we know, Bundy maintained caring relationships with family and partners. While these relationships may have been flawed, there's no reason to doubt their authenticity. The concept of "psychopathy" simply doesn't align with Bundy's profile.
Furthermore, using serial killer cases to support the existence of "psychopathy" should actually make us skeptical of this disorder. If the primary evidence researchers use to prove "psychopathy exists" consists merely of rough anecdotes about serial killers—and despite lacking empirical evidence, these anecdotes still convince researchers of the disorder's reality—then this indicates a powerful bias is secretly at play. And this bias is precisely what sustains the "zombie idea."
Third, psychopathy research is often depicted in academic textbooks and scientific articles as an ancient paradigm with centuries of scientific research history. They create an image that this field has been steadily advancing our understanding of psychopathy. However, this description of the paradigm is seriously misleading. In reality, this field has always been fragmented and struggled to gain footing in the scientific community. Until the 1980s, researchers remained deeply divided on "how to define psychopathy," unable even to agree on "what specific phenomenon they were studying."
This chaotic situation once drew fierce criticism from giants in psychology and psychiatry. In 1974, psychiatrist Aubrey Lewis described psychopathy as "the most elusive category in psychiatry." In 1975, psychologist Hans Eysenck called it a "white elephant": a useless burden impossible to discard. Historian Henry Werlinder noted that by the 1970s, labeling psychopathy as a "wastebasket diagnosis" had become commonplace: if no other suitable diagnosis existed, this label could be slapped onto patients. As late as 1988, influential forensic psychologist Ronald Blackburn still argued that psychopathy was merely a fictional entity that should be abandoned, characterizing it as a moral stigma disguised as a clinical diagnosis.
▷ Psychologist Hans Eysenck, whose core contribution was proposing the three-factor model of personality. Interestingly, a 2019 King's College London survey found that approximately 60 of this famous psychologist's papers were retracted due to lack of scientific rigor in their results and conclusions. Source: Nick Rogers/ANL/Rex
Overall, a forgotten fact about psychopathy research is this: until the 1970s and 1980s, there was a broad consensus in the mental health field that psychopathy, as defined by Cleckley, Hare, and others, might not be a real concept. As the most renowned advocate of psychopathy at the time, Cleckley himself had to swallow this bitter pill in the foreword to the fifth edition of The Mask of Sanity in 1976. Bitterly, he denounced his colleagues' indifference as a global "conspiracy of avoidance." He tried desperately to sell the concept of the "psychopath" to the world, but his colleagues simply wouldn't buy it.
Drivers and Ultimate Conclusion of the Psychopathy Research Boom
Therefore, a thought-provoking phenomenon emerges: why did psychopathy research, neglected and mocked in the 1980s, rapidly transform into one of the most revered fields by the 1990s? In less than a decade, interest in psychopathy research exploded.
▷ Woody Harrelson and Juliette Lewis in Natural Born Killers (1994). Image courtesy of Warner Bros.
What triggered this explosion of research interest? While no definitive answer exists, influential criminologist Shadd Maruna recently speculated it was partly forced-matured by the "tough-on-crime" political movement peaking in the 1990s. Other possible factors include our culture's overall obsession with the topic—evident in box-office hits like The Silence of the Lambs (1991), Natural Born Killers (1994), and American Psycho (2000). This cultural fervor may have incentivized psychologists to delve deeper into the concept.
Regardless of what drove this research interest, hindsight allows us to confirm one thing: this academic frenzy was absolutely not due to breakthroughs in empirical data. The evidence supporting common claims about psychopathy back then was as weak as it is today. The main difference now is that we have thoroughly tested this concept through hundreds of studies and found nothing. Today, we have sufficient empirical grounds to discard this concept, or at least maintain high skepticism toward it.
And this might be the strongest evidence that "psychopathy is a zombie idea": since scientists began studying this concept, evidence-based knowledge has never made any progress. On the contrary, increasing evidence indicates this concept is worthless. Yet, a large number of researchers remain interested, likely driven merely by their own biases and the concept's infectiousness.
The aggregation of scientific evidence has not confirmed the existence of psychopathy; instead, it has cast the entire concept into doubt.
Of course, nailing psychopathy to the耻辱 column of "zombie ideas" will inevitably provoke fierce backlash from numerous researchers and clinicians, which is entirely understandable. This viewpoint itself is speculative and deserves careful scrutiny. Some critics might point out that a few studies actually seem to confirm certain common claims about psychopathy. They might mention James Blair's 1995 study, which claimed to show moral psychological deficits in psychopaths; or critics might insist that some neuroimaging studies found abnormal brain activation in psychopathic samples.
However, such attempts to revive the concept with one or two isolated papers hardly constitute serious academic discourse. Among behavioral scientists, there's an open secret: our research processes usually possess enough flexibility—so-called "researcher degrees of freedom"—that if you wish, you can almost exploit this flexibility to "fabricate" any desired conclusion in a single study (the notorious scandals of fabricated "precognition" and "priming effects" serve as precedents). This magic trick of conjuring astonishing data from thin air, mockingly termed "false-positive psychology" within the field, precisely indicates how cautious we should be when drawing conclusions from single or even a few studies.
The good news is that the confusion caused by false-positive psychology is limited. As the number of studies increases and evidence accumulates, meta-analytic reviews ultimately present results closer to the truth. And this is precisely the problem facing psychopathy researchers: the aggregation of scientific evidence has not confirmed psychopathy's existence; instead, it has cast the entire concept into doubt.
If, after reading this, you still refuse to believe psychopathy is a zombie idea, you absolutely cannot bypass the core question: how do we explain the massive number of null results from hundreds of studies on psychopathy over decades? Personally, I have thought long and hard about this question. But apart from the answer provided in this article, I have yet to find a better explanation. This concept is already "dead." It's time for scientists to tear off its disguise, stare directly at this zombie's true face, and loudly proclaim its death to the world.
Original link: https://aeon.co/essays/psychopathy-is-a-zombie-idea-why-does-it-cling-on
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