Patrick Bateman, the Joker, Dexter, Alex DeLarge. They come from very different fictional worlds, but they share a familiar and unsettling set of traits: a capacity for cruelty, delivered with apparent nonchalance – sometimes even glee.
We usually label characters like these psychopaths or sociopaths – people who show little remorse, act impulsively and manipulate others for personal gain. In everyday language, the two terms are often used interchangeably.
In psychology, though, they are not treated equally.
Researchers have spent more than 120 years studying psychopathy, identifying personality patterns, genetic influences and brain regions that may be involved. But look for equivalent research on sociopathy and you’ll find far less.
While you might suspect a failure of scientific effort or perhaps a global conspiracy to suppress psychological research, the answer is actually simpler.
Though it was once a scientific term that meant something similar to psychopathy, researchers stopped using the term long ago as they moved on to different terminology.
“There are lots of scales, official, validated, well-designed scales for measuring psychopathy,” says Abigail Marsh, a professor of psychology and neuroscience at Georgetown University, in the US, who’s published multiple research papers on psychopathy.
“And there’s none of that for sociopathy. There’s no scientific society. You don’t really see it mentioned in journal articles.”
Though it’s vanished from science, the term sociopathy is alive and well in the real world, where you can find memoirs by self-described sociopaths like therapist Patric Gagne.
Sociopaths seem to abound on the internet as well, where the term has taken on an amorphous, ill-defined shape, used sometimes as a synonym for psychopathy, and sometimes to delineate a certain kind or gradation of psychopathic behaviour.
Pinning down the term may ultimately be pointless: to discuss the term sociopath is to first concede that no one really knows what it means, though plenty of people seem to have ideas.
The term sociopathy was first coined by German-American psychiatrist Karl Birnbaum in 1909 as he attempted to explain how factors in a person’s environment might lead them to act in ways that were antisocial.
To Birnbaum, it was society that pushed people to be callous or uncaring or delinquent, hence the ‘socio’ in sociopath.
Our modern conception of psychopathy, meanwhile, was popularised by the American psychiatrist Hervey Cleckley in his seminal 1941 work The Mask of Sanity, which offered case studies of people with many of the clinical traits recognised today, including superficial charm, habitual lying, lack of remorse and insight, and egocentricity.
Making matters worse, neither psychopathy nor sociopathy is an official psychiatric diagnosis. Open the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) – the handbook clinicians use to classify mental health conditions – and you won’t find either term listed.
What you will find is antisocial personality disorder (ASPD) – a broader category marked by a long-term disregard for others’ rights.
It covers many traits we associate with psychopathy, from deceitfulness and impulsivity to aggression and lack of remorse, but it is not the same thing.
Though we’ve yet to arrive at a point of terminological clarity, the psychopath-sociopath divide does illuminate a key debate in the field.
Years of psychological research do point to distinct subtypes of psychopathy, and hint at different paths to psychopathic behaviour, arguing for the need for new names to describe them.
Better understanding these distinctions isn’t just a matter of semantics. The way we draw these lines shapes diagnosis, treatment and whether people with these traits are seen as monsters – or as individuals who might benefit from the right support.
Hot and cold
So where does sociopathy end and psychopathy begin?
One possibility is that it doesn’t – at least not in the way pop culture suggests. What many people call ‘sociopathy’ today closely resembles what researchers describe as ‘secondary psychopathy’, says Marsh.
In that view, sociopathy isn’t a separate condition so much as a different label for a particular subtype.
The distinction comes largely from the work of Canadian psychologist Robert Hare, who developed the Psychopathy Checklist – Revised (PCL-R), one of the most widely used tools for assessing psychopathic traits.
The checklist breaks psychopathy into 20 characteristics, grouped into two broad factors.
‘Factor 1’ captures the interpersonal and emotional traits: superficial charm, manipulativeness, pathological lying, a lack of remorse and emotional coldness.
By contrast, ‘Factor 2’ reflects a more chaotic lifestyle – impulsivity, a constant need for stimulation and chronic irresponsibility.
The two factors resemble a common distinction between psychopathy and sociopathy that goes something like this: Psychopaths are rational and calculating, while sociopaths are violent and reactive – a kind of hot versus cold, if you like.
Marsh says the jury is still out on whether we can cleanly classify people as primary or secondary psychopaths – or psychopaths and sociopaths, if you like.
Researchers have yet to show conclusively that everyone with psychopathic traits falls into either a ‘hot’ or ‘cold’ category.
Still, some research comparing the two groups shows meaningful differences.
For instance, one study found that only people with secondary psychopathy were impulsive, while another noted higher levels of anxiety, depression and suicidal ideation for secondary psychopaths compared to primary psychopaths, who experienced those things at similar rates to the general population.
The divide even shows up in something called executive function – the brain’s ability to plan, stay organised, remember information and rein in impulses.
Studies have linked secondary psychopathy to executive dysfunction: poorer self-control, weaker planning ability and more difficulty regulating behaviour. Primary psychopathy shows the opposite pattern, with fewer signs of these problems.
These contrasts have led some psychologists to question whether the two profiles even belong under the same umbrella.
Randall Salekin, a professor of psychology at the University of Alabama, in the US, argues that primary and secondary psychopathy can seem almost in tension with each other – especially when it comes to emotion.
“There would be some people who would say the two sets of symptoms don't go together,” Salekin says. “How could you be cold, lacking in emotion, lacking in affect… and then at the same time, irritable, anxious, concerned?”
Marsh has observed the same divide in people diagnosed with – or suspected of having – psychopathic traits.
“Some of them are very anxious and dysregulated and some of them are very cold, with low emotion, and not particularly hostile but just don’t care about people,” she says. “I think we’re still struggling to understand how it all fits together.”
Taken together, their comments capture the uncertainty at the heart of the debate.
If these profiles differ so markedly in behaviour, cognition and emotion, it raises a serious question: is ‘sociopathy’ merely a subtype – or are we forcing two distinct patterns into a single box?
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Born or made?
A popular way of drawing the line between sociopaths and psychopaths is through nature versus nurture.
Some past researchers describe sociopaths (and secondary psychopaths) as products of their environment – made, not born. Primary psychopaths, by contrast, are assumed to be the inevitable result of genetics.
It’s a neat story. But Salekin isn’t convinced this divide holds up.
“I don't know if that’s a good distinction,” he says. “There’s just a lot more research to be done on what that means when [psychopathic behaviour] comes from the environment versus when it comes from genes.”
In reality, the picture is likely far more entangled. Most researchers now view psychopathic traits as the product of an interplay between genes and environment, not one or the other.
Recent research indicates that the heritability of antisocial behaviour, including psychopathic traits, is around 50 per cent, though the number varies across studies.
In other words, genes are perhaps half the reason someone may act callously or dangerously impulsive – the rest comes from the environment, especially their childhood.
Research has linked antisocial traits to factors such as maltreatment in the first 18 months of life, childhood abuse and broader psychosocial deprivation. These experiences don’t guarantee someone will develop psychopathic characteristics – but they can tilt the odds.
And for some, the process may become self-reinforcing.
Marsh suggests that people with genetic or environmental risk factors for antisocial personality disorder (ASPD) or psychopathy can slip into a feedback loop: antisocial behaviour provokes negative reactions from others, which in turn deepen mistrust and hostility.
“It’s the bad behaviour that is reinforcing all of these negative beliefs about people and about the world and yourself to some degree,” she says.
Over time, that cycle can harden, making it increasingly difficult to disentangle cause from consequence.
The real split
If we’re struggling to draw a clean line between psychopaths and sociopaths, it may be because our categories are too limited to begin with.
The way we currently divide psychopathy – into primary and secondary types, or into ‘psychopath’ versus ‘sociopath’ – may not fully reflect the diversity of traits involved. Some researchers argue we need a broader rethink.
One influential proposal is the triarchic model of psychopathy. Rather than splitting people into two camps, it breaks psychopathic traits into three dimensions: disinhibition, boldness and meanness.
Each is thought to have partly distinct genetic roots and neural underpinnings, though there is overlap.
Under this framework, someone might show high boldness without much meanness, or strong disinhibition without emotional coldness.
While the jury is still out on whether possessing one or two of these traits is enough for someone to qualify as a psychopath, Salekin says it’s the combination of all three that typically leads to issues, and perhaps a diagnosis.
“That’s when they have the worst outcomes in terms of conduct problems, substance use, problems in school and other things,” he says.
With more research, he thinks psychologists will be able to better understand the brain regions behind issues in each of the three buckets – emotional deficits may come from the amygdala, for example, and self-other comparison deficits from the medial prefrontal cortex – helping to better delineate exactly what’s at the root of these behaviours.
But even as the debate over labels continues, Marsh worries that the argument over definitions may be missing the bigger picture. However we categorise it, persistent antisocial behaviour has real consequences.
“There’s this enormous problem out there in the world of 1–2 per cent of the population who are persistently antisocial and account for up to two-thirds of all violent crime, according to some studies,” she says.
“They don’t want to be this way. They’re the ones whose lives are getting ruined, in addition to the other people.”
What to look for
Whatever term we use – psychopath, sociopath, primary, secondary – researchers agree that a small percentage of the population, usually estimated at around 1–2 per cent, shows a persistent cluster of traits such as lack of concern for others, manipulativeness, deceitfulness and grandiosity.
But spotting someone with these traits is harder than it sounds.
If the stereotype is of a visibly cold or volatile villain, reality is subtler.
Many people with high psychopathic traits – particularly those associated with so-called primary psychopathy – are adept at masking their inner world. They can appear confident, engaging and even unusually charming.
“I have found that if somebody who has psychopathy wants you to like them, you will like them,” Marsh says.
While it’s tempting to read into behaviour that seems callous or cruel and call it psychopathy, there are many other potential explanations, ranging from a simple bad day to other kinds of personality disorders like paranoia or schizophrenia.
Actual psychopathy is distinct from these things.
Marsh’s research bears that out, showing that people with psychopathy look different at the level of brain functioning than people at risk of antisocial disorders.
For instance, in a 2025 study, Marsh and her colleagues followed the same group of participants over time to examine how two factors – callous-unemotional traits and childhood maltreatment – shaped brain development.
Both were linked to changes in the amygdala, a region involved in processing emotion. But they did so in different ways.
“Those seem to be two independent influences on amygdala structure and to some degree function,” she says. “So, it’s at least a suggestion that there are multiple routes into being antisocial.”
Ultimately, finding a psychopath isn’t something the average person can do based on a few interactions, Salekin thinks.
“I think it’d be very difficult to spot someone unless you had a lot of information and time with them and it would probably be helpful to have training in clinical psychology or psychiatry,” he says.
Marsh advises anyone who thinks they may be dealing with psychopathic behaviour to keep close track of someone’s actions, ideally across different situations.
A telltale pattern is someone who uses others to get what they want – whether that’s by being charming or aggressive.
One big mistake many people make is to let their own feelings get in the way, she says. Many people may decide someone is a psychopath simply because they don’t like them, and vice versa.
As for spotting a sociopath, that may be impossible, given the absence of a true definition. The word may only survive in headlines and crime dramas.
In science, though, the focus is shifting: away from catchy categories and towards a more precise understanding of the traits – and brains – that drive antisocial behaviour.
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