As an expert on personality disorders, people often ask me about psychopathy. It seems everybody has had an ex, a boss, a neighbour or a relative who they suspect has traits of it. People are curious about how to recognise psychopathy, and whether it can explain certain harmful behaviour. It’s easy to see why. Psychopathic people are everywhere – from books and movies to newspaper articles and academic papers.
But while such questions are usually asked with confidence, the answers are far less straightforward. In fact, a growing number of academic papers have failed to find evidence that psychopathy exists at all. Could the disorder be something we’ve just invented because it’s convenient, doing away with old concepts of good and evil? Some experts believe so. But I am not so sure.
Psychopathy is normally identified by a few specific traits. These include a lack of empathy and remorse, callousness, impulsiveness, shallow emotions, arrogance and manipulation.
We’ve all come across people who have a combination of these traits. Perhaps they are emotionally detached, cruel, untruthful or even violent. There is no denying that such characteristics exist. What is difficult to prove is that people with psychopathy actually have those traits. Why? I believe it’s down to a mismatch between what we expect psychopathy to look like and how personality actually unfolds in the real world. And this gap is where much of the confusion begins.
The empathy paradox
A recent systematic review of empathy research, which included 66 studies and 5,711 people assessed with a common tool called the Hare Psychopathy Checklist (PCL), found that 89% of all tests failed to show that those with psychopathic traits were less empathetic than others. If psychopathy is defined by a lack of empathy, why is it so difficult to demonstrate? At first glance, this seems like a serious challenge to the concept itself.
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A similar lack of clear evidence has been found for other traits often linked to psychopathy. Research examining shallow emotions, in particular a lack of fear, using measures such as skin conductance (which can estimate sweating), startle reflexes and autonomic arousal (increased heart rate) has often produced mixed findings. Claims that people with psychopathy have extreme impairments in moral reasoning have likewise been challenged.
In fact, recent reviews have questioned whether any single deficit in a specific trait can be consistently linked to psychopathy. So what’s going on?
As we shall see, the issue may not be that empathy, immoral reasoning or a lack of fear is absent in those with psychopathy, but that these traits are being measured in overly narrow ways.
A zombie idea?
Some researchers have taken these inconsistencies a step further. In a recent essay in Aeon, one of the authors behind this body of work argues that psychopathy may be what researchers call a “zombie idea”. This refers to a concept that continues to be widely accepted despite weak or inconsistent evidence, like the old idea that the Earth was at the centre of the universe.
The idea is that psychopathy persists because it is intuitively appealing. Like outdated scientific beliefs that lingered long after being challenged, it offers a compelling explanation for behaviour that is otherwise difficult to understand.
It’s an interesting thought. Psychopathy is culturally familiar and has long been associated with extreme and disturbing behaviour. This makes it an attractive concept for explaining antisocial acts – it offers a seemingly objective framework for behaviour that can feel deeply unsettling. It provides a sense of certainty in situations that are complex and uncomfortable.
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Take the rapist and serial killer Ted Bundy. Even when he faced justice for his heinous crimes, Bundy didn’t show remorse – always sporting a movie star smile. This is impossible for most people to comprehend, and Bundy has been branded as psychopathic countless times. This has in turn helped to shape public and scientific ideas about what the label means.
But this is precisely where the problem lies. Human behaviour is rarely so clear-cut. Bundy himself had a range of different problems that may have contributed, including obsession and substance abuse issues. The appeal of psychopathy as a concept may come from its simplicity – the idea that there is a distinct type of person who lacks empathy and poses a clear risk. The reality is likely to be far more nuanced. And the “zombie idea” argument forces us to confront the possibility that the concept has endured because it is useful rather than well-defined – academically, forensically and culturally.
How psychopathy is measured
To understand why the evidence is so mixed, let’s look at how psychopathy is actually assessed. In psychiatric and forensic settings, it is most commonly measured using structured tools such as the Psychopathy Checklist-Revised (PCL-R). This approach combines interview data with information about a person’s behaviour and life history.
This means that clinicians consider traits such as superficial charm, grandiosity, pathological lying and lack of remorse alongside behavioural patterns such as repeated rule-breaking, unstable relationships, poor work history, aggression, early conduct problems and criminal records.
This has proven useful in prisons and psychiatric units. Recent evidence, drawing on many studies, suggests the PCL-R can indeed help identify future risky behaviour in such settings, particularly in relation to re-offending and institutional misconduct. This implies that structured assessments may capture something clinically relevant in high-risk populations.
Nicole Piepgras/Shutterstock
Another issue is that psychopathy is not included as a formal diagnosis in the Diagnostic and Statistical Manual of Mental Disorders (DSM). Instead, it overlaps with antisocial personality disorder, which focuses more on patterns of behaviour such as rule-breaking, impulsivity and aggression.
This creates an important tension. Psychopathy is often used to describe underlying personality traits, while antisocial personality disorder is defined by observable behaviours. In practice, these do not always align. Someone may engage in harmful behaviour without displaying the emotional features associated with psychopathy, while others may show emotional detachment without criminality.
This ambiguity is not just a technical issue. It shapes how the construct is used in practice. In forensic settings, psychopathy is often treated as a meaningful indicator of risk. But if the boundaries of the construct are unclear, then its application becomes more difficult to justify.
The real problem: measurement
A large part of the difficulty may therefore lie in how we measure psychopathy – and the traits we believe underlie it.
Importantly, many of the studies included in the recent psychopathy and empathy review used the PCL-R in forensic settings, meaning psychopathy was often assessed through structured clinical interviews alongside criminal histories and file reviews. In other words, the psychopathy assessments themselves were frequently extensive and clinically informed.
Yet despite this, the evidence linking psychopathy to empathy deficits remained inconsistent. This suggests the problem may lie less in identifying psychopathic traits themselves and more in how empathy is tested.
Many studies rely on narrow laboratory tasks or self-report questionnaires designed to capture specific components of empathy, such as recognising facial expressions, in controlled settings. While these methods offer experimental control, they may fail to reflect how empathy operates in real-world relationships, conflicts and situations involving personal gain.
The recent review on psychopathy and empathy, for example, drew on a wide range of standard empathy measures, including self-report questionnaires and laboratory tasks such as recognising emotions in faces or voices, interpreting photographs of eyes, or responding to hypothetical scenarios. These are established tools, but they often assess specific components of empathy rather than how empathy operates in real-world relationships, conflicts or situations involving personal gain.
Empathy is not a single ability. It involves recognising emotions, understanding perspectives and responding appropriately. Someone may be able to recognise distress without feeling concern, or understand another person’s perspective without acting on it. These distinctions are rarely captured in simple tests. Different studies may be measuring different aspects of empathy, leading to apparently contradictory results.
For example, how someone responds to distress may depend on who the other person is, what the relationship is and what is at stake. These are not variables that can easily be reproduced in a laboratory setting. A person with psychopathy may in fact have some level of basic empathy, as measured on these tests, but be able to completely switch it off when it’s in their interest. As a result, the findings may tell us more about how people perform in artificial laboratory conditions than how they behave in everyday life.
In this sense, researchers may be trying to capture a complex pattern of traits using tools that are too narrow to detect it reliably.
In other academic studies, the measurement of psychopathy in itself could be a problem. When psychopathic traits are measured in the general population, such as students or people taking tests online, they often rely on self-report questionnaires rather than the full PCL-R – asking people about to assess their own thoughts, feelings and behaviour. Such studies were indeed included in the review about moral reasoning and psychopathic traits.
But psychopathy is, after all, famously linked to lying and manipulation, pointing to a deeper paradox. Researchers are relying on self-report measures to assess traits that, by definition, involve deception. If someone is motivated to present themselves in a certain way, or does not recognise their own behaviour as a problem, then their responses may not reflect their underlying traits.
Different kinds of psychopathy?
Another issue is how psychopathy has traditionally been framed in clinical practice. It is often treated as a distinct category – something a person either is or is not. But research on personality more broadly suggests that traits exist on a spectrum. Characteristics such as empathy, impulsivity and emotional regulation vary across individuals rather than being confined to a specific group.
If psychopathic traits are distributed along a continuum, then it is perhaps unsurprising that studies struggle to find clear-cut differences between groups. What looks like inconsistency in the evidence may instead reflect the fact that we are trying to draw firm boundaries around something that is inherently gradual and variable.
This shift is already reshaping how personality disorders are understood more broadly, moving away from rigid categories.
Even within traditional models of psychopathy, researchers have long recognised that psychopathic traits can vary. The PCL-R, for example, separates Factor 1 traits such as superficial charm, grandiosity, manipulation and lack of remorse from Factor 2 traits such as impulsivity, aggression, irresponsibility and chronic rule-breaking.
These two dimensions often relate to different outcomes and may appear in different combinations. For example, there may be more Factor 1 personality traits without severe antisocial behaviour in the general population, while there are more elevated Factor 2 traits in prisons. This means that studies focusing on different samples may appear inconsistent – measuring different parts of the same broader construct.
A useful comparison can be found in research on narcissism. Narcissism was once treated as a single construct, typically associated with grandiosity and entitlement. However, it is now widely understood to include distinct forms, such as grandiose and vulnerable narcissism.
Grandiose narcissism is characterised by confidence, dominance and a sense of superiority. But, as I and other researchers have shown, vulnerable narcissism, by contrast, is associated with insecurity, hypersensitivity and emotional reactivity. Both fall under the same broader construct, but they present very differently in everyday life.
This distinction matters because it shows how a concept can appear inconsistent until its underlying variation is recognised. Psychopathy may be in a similar position. What appears to be conflicting evidence in the literature may reflect the fact that different studies are capturing different aspects of a broader construct, often using different measures of psychopathy to do so.
Gender differences
Another limitation is that much of the initial research on psychopathy has been conducted in male, forensic samples – often focusing on people in prison. These have then been used to develop general tests of psychopathy that may not be relevant to a general population of men and women who are not criminals.
Traits associated with psychopathy may present differently outside these contexts. In women, for example, these traits may be expressed in more relational ways – through patterns of manipulation, emotional detachment and aggression that is less overt.
Some studies have suggested that women who commit violent crimes tend to score relatively higher on interpersonal and affective traits (closer to Factor 1) than on the overtly antisocial behaviours (captured by Factor 2), compared with male violent offenders. This may help explain why female presentations can be overlooked when assessment tools are heavily skewed towards male behaviour.
A similar pattern has been observed in narcissism research. Early models focused heavily on externally visible traits, such as overt grandiosity, entitlement and assertiveness, which are more commonly associated with men. Only more recently has vulnerable narcissism – defined by low self-esteem, hypersensitivity, and feelings of shame – been recognised as more typical of female expressions of narcissism.
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If our understanding of psychopathy is based on a narrow subset of individuals, then it’s likely to miss important variations in how these traits are expressed.
Why this matters
Taken together, these issues help explain why psychopathy can feel both familiar and elusive. The traits often associated with it – emotional detachment, reduced empathy, impulsivity – do exist and appear in real interactions. But they rarely present in the clear, consistent way that diagnostic labels suggest.
Instead, they emerge unevenly, shaped by context, relationships and other aspects of personality. This gap between real life and formal measurement has real-world consequences. In prisons, it can influence decisions about risk, sentencing and rehabilitation. And in the workplace, it may mean that employers miss psychopathic traits in the people they promote – they may appear charming and reliable to those who are senior to them – leading to chaos and suffering among staff.
Rather than asking whether psychopathy exists, a more useful question may be why it has been so difficult to define and measure in a consistent way.
The evidence does seem to suggest that it may be too narrowly framed and too simply measured. A more effective approach may involve treating these traits as existing along a continuum, recognising their variability across people and contexts and combining multiple methods of assessment rather than relying on any single tool. For example, this might include integrating clinical judgement with patterns of behaviour over long periods of time to build a more complete picture of how these traits manifest.
Seen in this light, psychopathy may not be a “zombie idea” after all. Perhaps it is just a concept that we have yet to fully understand. The challenge is not to abandon it, but to refine how we study it – and how we interpret what we find.
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