Brainwaves reveal two different biological roots for psychopathic behavior

Different psychopathic personality traits change how the brain allocates attention and processes emotions. Research published in the journal BMC Psychology shows that traits like boldness alter focus, while traits like meanness blunt emotional reactivity to distressing images. These distinct mechanisms offer a more nuanced view of the biological roots of psychopathic behavior in the general population.

Psychopathy is not a single, uniform condition. Psychologists often describe it as a collection of distinct personality characteristics that appear to varying degrees in everyday people. The widely used triarchic model divides these characteristics into three main categories, which include boldness, meanness, and disinhibition.

Boldness involves social dominance, emotional resilience, and a lack of fear. Meanness is characterized by a lack of empathy, a tendency to exploit others, and callousness. Disinhibition describes impulsive behavior, irritability, and difficulty regulating urges.

Researchers have debated the underlying causes of these traits. One well supported theory suggests that psychopathic behavior comes from a basic emotional deficit. Under this idea, the brain fails to generate normal feelings of fear or empathy due to underactive sensory regions.

Another theory proposes an attentional bottleneck. This concept suggests people with psychopathic traits focus so intensely on a goal or a primary stimulus that they fail to process secondary information. Overactivity in the prefrontal cortex might drive this intense focus, causing the person to ignore peripheral threats or another individual’s distress.

This line of research aligns with modern scientific frameworks that view mental health conditions as spectrums rather than strict categories. The National Institute of Mental Health encourages studying how these traits manifest in the general community. By looking at mild versions of these traits, scientists hope to uncover the basic biological circuitry that drives behavior before it reaches a clinical or criminal threshold.

To test these competing ideas, Ting-Fang Soong, a neuroscience researcher at Erasmus Medical Center, organized a study with a team of collaborators in the Netherlands and Australia. The group wanted to see if specific brain responses could separate attentional deficits from emotional deficits. They aimed to map these responses to the distinct traits of boldness, meanness, and disinhibition.

Soong and the research team recruited 115 healthy adults for the experiment. The participants did not have criminal backgrounds or clinical psychiatric diagnoses. Assessing a community sample allowed the researchers to study how psychopathic traits function along a normal spectrum.

Participants first completed self-report surveys to measure their levels of boldness, meanness, and disinhibition. They also filled out questionnaires to gauge their general capacity for cognitive, affective, and somatic empathy.

The researchers then had the participants view a series of positive, negative, and neutral images on a smartphone mounted on a stand in front of them. The negative images included distressing scenes like victims of injury, while positive images included cute animals.

While viewing these images, participants occasionally heard a loud burst of white noise delivered through headphones. This noise acts as a startle probe. In human beings, a sudden loud sound triggers an involuntary defensive blink managed by basic survival circuits in the brain.

To measure this reflex continuously, the researchers used a smartphone application called BlinkLab. The software tracked facial landmarks through the phone’s front facing camera and calculated the exact intensity of each participant’s startle blink.

At the same time, participants wore caps lined with electrodes to record electrical brain activity. The researchers monitored specific brainwave patterns known as event-related potentials. One pattern indicates a shift in involuntary attention, while another pattern reflects prolonged emotional processing.

By presenting the loud noise at different intervals after an image appeared, the scientists could track how attention and emotion shifted in real time. They triggered the noise at 50, 700, and 4500 milliseconds after the image showed up on the screen.

The results revealed that separating psychopathic traits connects them to entirely different brain responses. The researchers found support for both the emotional deficit theory and the attentional bottleneck theory, depending on the specific trait being evaluated.

For example, boldness was associated with a strong attentional bottleneck, particularly in male participants. When men with high boldness scores looked at negative images, their brains showed an exaggerated spike in the attention related brainwave at the 700 millisecond mark.

At this fraction of a second, the brain is usually highly engaged in processing the visual scene. The intense focus meant these individuals directed fewer mental resources to the sudden loud noise.

This finding suggests that bold individuals do not necessarily lack the biological hardware to process threats. Instead, their attention becomes highly fixated on what is right in front of them. This limits their ability to register other things happening in their environment.

Meanness, by contrast, lined up closely with the emotional deficit theory. Participants with high meanness scores reported lower levels of both affective and somatic empathy on their initial surveys. During the experiment, they showed a muted startle blink when looking at negative images, specifically at the 4500 millisecond mark.

Typically, looking at a distressing image for several seconds primes the human nervous system to be on guard. This usually results in a much harder protective blink when a sudden noise occurs. The lack of this heightened reflex in people with high meanness indicates a blunted physiological reaction to distressing situations.

When participants scored high in both boldness and meanness, they also showed weaker brainwave responses associated with processing complex emotions. This suggests that the two traits can combine to suppress empathic responses even further.

The third trait, disinhibition, did not show any relationship to the emotional or attentional biological markers measured in this experiment. The researchers suggest disinhibition might be driven by different neural mechanisms related to impulse control rather than fundamental shifts in fear processing or visual attention.

The study relies on a relatively specific experimental setup, which presents certain limitations. The image database used to elicit emotions contained distressing visual content, but it did not feature extreme, direct threat scenarios. Using highly threatening imagery might have produced greater variation in the startle reflexes.

The researchers also noted that repeatedly using a loud noise could create an anticipatory effect among the participants. After several trials, subjects might have started to expect the startle probe. This anticipation could alter how their brains allocated attention at the later time intervals.

Future projects will need to broaden the scope of the testing environments. The researchers recommend testing these concepts in larger groups to better understand potential differences between men and women. They also plan to see if these patterns hold up in clinical populations, such as individuals diagnosed with severe personality disorders.

Understanding the biological roots of these traits could eventually help psychologists design better early interventions. If a person’s antisocial behavior stems from an attentional bottleneck, treatment might focus on cognitive therapies that broaden their awareness. If the behavior stems from an emotional deficit, therapeutic methods could target emotional pathways instead.

The study, “Emotional and attentional anomalies underlying triarchic psychopathic traits: an EEG-startle blink study,” was authored by Ting-Fang Soong, Jordi P. A. Booij, Katharina Stapel, Carolien Bunnik, Iris Zwilling, Antonia Karp, Sebastiaan K.E. Koekkoek, Kayleigh D. Gultig, Lotte E.M. Roggeveen, Cornelis P. Boele, Chris I. De Zeeuw, Henk-Jan Boele, and Josanne D. M. van Dongen.