Scientists Have Established a Key Biological Difference Between Psychopaths and Normal People

Human Brain Neural Network Cerebral Cortex

The research found that the striatum region of the brain was on average ten percent larger in psychopathic individuals compared to a control group of individuals that had low or no psychopathic traits.

A new study has shown that psychopathic people have a bigger striatum area in their brain

Neuroscientists using MRI scans discovered that psychopathic people have a 10% larger striatum, a cluster of neurons in the subcortical basal ganglia of the forebrain, than regular people. This represents a clear biological distinction between psychopaths and non-psychopathic people.

Neuroscientists from Nanyang Technological University (NTU Singapore), the University of Pennsylvania, and California State University have discovered a biological distinction between psychopaths and non-psychopaths. Using magnetic resonance imaging (MRI) scans, scientists discovered that the striatum, an area of the forebrain, was 10% bigger in psychopathic people compared to a control group of individuals with low or no psychopathic traits.

Psychopaths, or those with psychopathic qualities, are people who have an egotistical and antisocial disposition. This is often characterized by a lack of guilt for their actions, a lack of empathy for others, and, in some cases, criminal tendencies.

The striatum, which is part of the forebrain, the subcortical region of the brain that encompasses the whole cerebrum, coordinates numerous elements of cognition, including motor and action planning, decision-making, motivation, reinforcement, and reward perception.

Previous research has shown that psychopaths have overactive striatum, but the influence of its size on behavior has yet to be confirmed. The new research demonstrates a significant biological difference between people who exhibit psychopathic tendencies and those who do not. While not all people with psychopathic qualities end up violating the law, and not all criminals satisfy the criteria for psychopathy, there is a strong association. There is also significant evidence that psychopathy is associated with more aggressive behavior.

The understanding of the role of biology in antisocial and criminal behavior may help improve existing theories of behavior, as well as inform policy and treatment options. To conduct their study, the neuroscientists scanned the brains of 120 participants in the United States and interviewed them using the Psychopathy Checklist-Revised, a psychological assessment tool to determine the presence of psychopathic traits in individuals.

Assistant Professor Olivia Choy, from NTU’s School of Social Sciences, a neurocriminologist who co-authored the study, said “Our study’s results help advance our knowledge about what underlies antisocial behavior such as psychopathy. We find that in addition to social environmental influences, it is important to consider that there can be differences in biology, in this case, the size of brain structures, between antisocial and non-antisocial individuals.”

Assistant Professor Olivia Choy, a neuroscientist from NTU’s School of Social Sciences, currently presenting diagrams of the human striatum. Credit: NTU Singapore

Professor Adrian Raine from the Departments of Criminology, Psychiatry, and Psychology at the University of Pennsylvania, who co-authored the study, stated “Because biological traits, such as the size of one’s striatum, can be inherited to a child from a parent, these findings give added support to neurodevelopmental perspectives of psychopathy – that the brains of these offenders do not develop normally throughout childhood and adolescence.”

Professor Robert Schug from the School of Criminology, Criminal Justice, and Emergency Management at California State University, Long Beach, who co-authored the study, added “The use of the Psychopathy Checklist-Revised in a community sample remains a novel scientific approach: Helping us understand psychopathic traits in individuals who are not in jails and prisons, but rather in those who walk among us each day.”

Highlighting the significance of the work done by the joint research team, Associate Professor Andrea Glenn from the Department of Psychology of The University of Alabama, who is not involved in the research, stated “By replicating and extending prior work, this study increases our confidence that psychopathy is associated with structural differences in the striatum, a brain region that is important in a variety of processes important for cognitive and social functioning. Future studies will be needed to understand the factors that may contribute to these structural differences.”

The results of the study were published recently in the peer-reviewed academic publication Journal of Psychiatric Research.

Bigger striatum, larger appetite for stimulation

Through analyses of the MRI scans and results from the interviews to screen for psychopathy, the researchers linked having larger striatum to an increased need for stimulation, through thrills and excitement, and a higher likelihood of impulsive behaviors.

The striatum is part of the basal ganglia, which is made up of clusters of neurons deep in the center of the brain. The basal ganglia receive signals from the cerebral cortex, which controls cognition, social behavior, and discerning which sensory information warrants attention.

In the past two decades, however, the understanding of the striatum has expanded, yielding hints that the region is linked to difficulties in social behavior. Previous studies have not addressed whether striatal enlargement is observed in adult females with psychopathic traits.

The neuroscientists say that within their study of 120 individuals, they examined 12 females and observed, for the first time, that psychopathy was linked to enlarged striatum in females, just as in males. In human development, the striatum typically becomes smaller as a child matures, suggesting that psychopathy could be related to differences in how the brain develops.

Asst Prof Choy suggested “A better understanding of the striatum’s development is still needed. Many factors are likely involved in why one individual is more likely to have psychopathic traits than another individual. Psychopathy can be linked to a structural abnormality in the brain that may be developmental in nature. At the same time, it is important to acknowledge that the environment can also have effects on the structure of the striatum.”

Prof Raine added “We have always known that psychopaths go to extreme lengths to seek out rewards, including criminal activities that involve property, sex, and drugs. We are now finding out a neurobiological underpinning of this impulsive and stimulating behavior in the form of enlargement to the striatum, a key brain area involved in rewards.

The scientists hope to carry out further research to find out the causes of the enlargement of the striatum in individuals with psychopathic traits.

Reference: “Larger striatal volume is associated with increased adult psychopathy” by Olivia Choy, Adrian Raine and Robert Schug, 6 March 2022, Journal of Psychiatric Research.
DOI: 10.1016/j.jpsychires.2022.03.006


View Comments

  • Uh oh... You base it on law(s), character definitions and such subjectivities? Then imply some guy living under a tree watching the same sunset every day for as long someone feeds him and that s it, would not be a psychopath! Basically the human brain is what it is and Modern times what they are because we sought not only comfort but stimulation! Uh, any unrecognized diseases affecting the relevant brain area? Only read the review but sounds needs more specifics to the correlation. Need for stimulation is a.symptom of intelligence and that is a concept not easily swallowed by not-so-modern societies, ie, most of the planet.

      • In the past, our society went through mass therapies, i.e. starvation before The First Thanksgiving, Wagon Trains to Oregon, WWII, The Great Depression. Psychopathic tendencies were mitigated by brutal reality.

        The current psychopathic deterioration of our society is a consequence of children of the Greatest Generation's total disregard for the lessons learned via brutal reality.

        This study could be used to design therapies that could mimic brutal reality lessons for those with psychopathic tendencies.

        But it won't because you cannot fill a cup which is already full of utopian pipedreams derived from the belief that there is no objective truth and that man is perfectible.

      • Like phrenology shape of the head early diagnostic tool discredited. I feel so many factors can play a part..childhood abuse..bad socio.economic conditions.Genetics. So in future we will just gene splice this out and give everyone a living wage..

    • Unfortunately, previous comments posted seem somewhat lacking in knowledge, education, experience and/or understanding of this subject. While I would agree the sample size of the test population of the subject is rather small/limited to draw substantive conclusions and further research is needed, the fact that any consistent correlation identified in these findings exists (i.e. brain scans), I feel, is significant and may be promising. That there may be some sort of tangible evidence of this condition, if validated, that may some day enable neuroscientists to further understand the root cause factors and information that may lead to finding treatment or, at least, education of the conditions during critical stages of brain development in childhood where early intervention might have a positive impact on the outcome of individuals with these conditions and, to a greater extent society as a whole, is both fascinating and exciting. I hope the scientific and medical communities will pursue continued research and exploration of the results presented in this study.

    • Such a person would most definitely not be a psychopath. Psychopath have overactive dopamine systems and are therefore extremely motivated to seek out experiences, regardless of the cost. Your hypothetical lazy guy under a tree suffers from an underactive dopamine system, which is the polar opposite. A very problematic behavior pattern for sure but not psychopathy. Such a person would be fairly easily treated though since ramping up dopamine is easily done with drugs.

      • There is no general correlation between brain size and behavior. That they may have found - small exploratory research - is a localized volume correlation.

        Interestingly the developing human brain pares down cells and synapses, so it may be that a smaller brain has "learned more/better".

        There is no contradiction between having developmental differences and taking responsibility (such as before criminal law). This is more suggestive of that some individuals should get treatment instead of prison (if the results bear up).

  • Unsupportable Assumption:

    "While not all people with psychopathic qualities end up violating the law, and not all criminals satisfy the criteria for psychopathy, there is a strong association."

    • They found a strong association if that is what they claim. In which case I guess you made your own "Unsupportable" claim.

      It is a small study, no need to get unduly excited either way.

  • This idea of "normal" is a good way to turn a phych classroom into a heated debate, well past bell. Being classified as "normal" to an insanely sick, greedy, consienceless capitalist just because our MRI's are the same makes me nauseus.

    • ? Politics don't come into it, nor do clustering results as those you mention.

      There are diagnostic criteria for some problematic behaviors, but the field is rather dire.

  • We've been made, on guard at once 🤣
    Either way people have to get by.. imagine.. out here it may leave anyone in a questionable position with the actions they take to get by, some with a more fortunate situation and some not as fortunate.. the righteous path to getting on ones feet may seem easy to someone who was handed the keys and forced into curriculum.. compare with someone who literally has to "dog it out" to get by and you'll create your own facade of what a psychopath really is, a brain development disorder or realistically someone with a mental health issue naturally or acquired from injury?
    Personally I refuse to be categorized by the shape of someones brain or put in question because of someone else's thought processing and based off what they would do in the situations they get into, who came up with the debate to question this anyway? someone with a mental health problem? Maybe even a think tank with a mental health problem! Categorizing individuals by the shape of their brains hmm what are we going to magically Splice and edit that out because it's unfit for society too? Whose idea is half the sh*t going on right now. Good people break bad.. I think the weirdest thing is the people you least expect are the ones out here doing bad things specifically the ones who think they're perfect with nothing wrong with them. That's simply my observation and perspective right or wrong, goto work do good and go above at times and you should be fine don't spoil yourself too much. I do have a question for the topic, how do we know there's a correlation and at that broadly enough to make assertions such as to classify said individuals into potential criminal groups.. treading down a dark avenue..

    • If it can be observed as significant, it is a fact. (In this case the study is small, so we don't know if it is a robust observation.)

      You can have your own opinions, but you can't have your own facts.

      • I was married for 12 years to a psychopathic narcissist with bipolar depression and an addiction to gambling and meth(I learnes this info approximately year 10). So if I can be of any help with reasarch, I'd be more than happy.

  • Your control groups were too selective and now you're implying that all people w8th enlarged striatum regions are psychopaths. Bad science.

  • Right! Wow, coming out of the woodwork. He sounds like my brother.. only not very great with grammar. Symptom of intelligence?!

    • Spending millions on a study like this is laughable. The extremely small of people examined to start.. Why don't they give their time and effort that will make a real change in this world like humans that shoot up other humans in massacres or finding a cute for cancer to name just a couple of examples. Absolute nonsense if you ask me. If they know so much about the brain how about doing a study to help millions suffering from mental illnesses? I don't know, maybe I'm off the

  • Uh....this is a bit far fetched don't ya think? What about those with nerological disorders such as ADHD, or Autism Spectrum Disorder? Wouldn't you imagine they too have a larger than average striatum? Since they are also "reward seeking", and basically live for stimuli. I would think any condition with symptoms similar to this type of behavior would be linked to having larger striatums. So please, don't stop with psychopaths...because it certainly doesn't end with them. 🖤

  • Thank you who ever you are that commented before me I won't get into details I just don't have the energy anymore to keep explaining. No one seems to care anyways. I really needed that to keep me from having a nervous breakdown. I've been trying to figure out on my own what's wrong with me or if there's even anything . Someone I love called me a bunch of names and abandoned me just like everyone one else in my life . All !! I don't understand I always tried to do the right thing even when nobody's looking. I always loved but now I'm not sure if I even know what love is

    • Sending you a hug and God is ❤️ love. He's everything to me I pray for you to know love. You deserve it too. Have a blessed day.

  • Even if you could show that all psychopaths have enlarged striatums, you cannot infer that all people with enlarged striatums are psychopaths. Though that is not precluded either.

    If the striatum is the part of the brain that schemes, then chess masters, and professional GO players would likely also have enlarged striatums, probably pro/college sports team coaches as well.

    It would be interesting to see if the genes they have found associated with psychopathy actually do anything that could result in this brain region being enlarged or more active.

    My suspicion is that this is just larger due to higher use, rather than anything genetic. Similar to weight lifting, producing larger muscles.

    This did surprise me. If anything, I would have suspected some area in the brain was atrophied rather than enlarged.

    • "If the striatum is the part of the brain that schemes,..."

      Your entire missive is centered around that conjuncture, which is not supported anywhere in the article nor in the literature I was able to look up. If you have evidence to support that conjuncture, please cite them. Otherwise the house of cards you built on that premise just falls flat.

      • "The basal ganglia receive signals from the cerebral cortex, which controls cognition, social behavior..." When I add "cognition" to "social behavior", that sounds like scheming to me, or planing if the person were normal.

        • You are also assuming larger volumes means more capability. But during development paring down the potential adult size and complexity of the brain is important for function.

          As almost everywhere else in biology, you have to interpolate between observations and not extrapolate.

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