Brain wave monitoring reveals how psychopathic traits disrupt trust and reward in social scenarios

People who score high in psychopathic traits are less likely to trust strangers and show distinct brain activity when evaluating social risks and financial rewards. An experiment using brain wave recordings suggests these individuals experience intense cognitive conflict when suppressing cooperative behavior and feel outsized disappointment when their expectations of a payout are violated. The research was published in the journal BMC Psychology.

While popular media often portrays psychopathy as a trait exclusive to violent criminals, psychologists recognize it as a continuous spectrum present in the general population. Psychopathic traits include manipulativeness, a lack of empathy, a preference for self-interest, and impulsivity. Because these traits heavily impact how a person interacts with others, researchers frequently study how individuals on the higher end of this spectrum navigate social decision-making.

Social interactions often rely heavily on generalized trust. Trusting a stranger is essentially a social gamble. If the other person honors the trust, both parties might benefit. If the other person acts selfishly, the trusting party might suffer a loss. Understanding how the brain weighs these outcomes provides a window into the biological mechanisms of human cooperation.

To observe this process, a team of researchers led by Fengbo Guo at Guangdong Medical University in China designed an experiment utilizing the Trust Game. The Trust Game is a classic tool in behavioral economics used to measure interpersonal trust and reciprocity.

The mechanics of the game are straightforward. A participant, acting as the “trustor,” receives an initial sum of virtual money. They must decide whether to keep the money or transfer it to an anonymous “trustee.” If they keep it, the round ends. If they transfer the money, the amount is multiplied, and the trustee then decides whether to split the larger pot evenly or keep it all for themselves. Providing the money demonstrates trust, while holding onto it demonstrates distrust.

The researchers screened over 300 healthy undergraduate students using a standard questionnaire designed to measure subclinical psychopathic traits. From this broad pool, they selected 44 participants. Half of these individuals scored in the top tier for psychopathic traits, while the other half scored in the bottom tier.

The participants played 150 rounds of the Trust Game while hooked up to an electroencephalogram, a device that monitors electrical activity in the brain. The participants were told they were interacting with human partners, but the trustees’ responses were actually fixed by a computer program. The game was designed so that transferring money would result in a fair split exactly half the time and a total loss the other half of the time.

Behaviorally, the participants with high psychopathic traits chose to trust their partners much less often than those with low psychopathic traits. The high psychopathic trait group chose to share their money about 53 percent of the time, compared to nearly 62 percent for the low psychopathic trait group. This aligns with past behavioral research characterizing psychopathic traits as predominantly self-centric and risk-averse in cooperative settings.

An unpredictable pattern emerged when the researchers looked at what happened immediately after a participant experienced a betrayal. The individuals with low psychopathic traits did not notably change their behavior after losing money. The participants with high psychopathic traits, on the other hand, chose to trust their subsequent partners more often right after being betrayed.

The authors propose that individuals with elevated psychopathic traits might view the game as a series of manipulative transactions. They might recognize that continuous betrayals are statistically unlikely, or they might attempt to recover their losses by gambling on a future payout.

The brain wave data captured during the decision-making stage offered clues about the mental effort required to navigate these choices. The researchers focused on a specific brain wave pattern called the N2 component. This electrical signal typically spikes in the frontal-central regions of the brain about 200 to 350 milliseconds after a person detects a conflict or exerts cognitive control.

In the participants with high psychopathic traits, choosing to distrust a partner generated a much stronger negative N2 signal compared to choosing to trust. The participants with lower psychopathic traits showed no such electrical difference between their choices.

This suggests that individuals with high psychopathic traits experience intense cognitive friction when making uncooperative decisions. Humans generally recognize cooperation as a standard social norm. The researchers suggest that people with high psychopathic traits understand this expectation completely, but they use mental effort to override the urge to conform to the norm in favor of securing an immediate personal advantage.

When the participants found out whether their trust had been validated or betrayed, their brains generated another set of distinctive signals. The researchers looked at a brain wave tied to reward prediction, which typically spikes when an expected reward does not materialize. This expectation-related signal is generated in the brain regions responsible for evaluating wins and losses.

Participants with high psychopathic traits exhibited a vastly stronger brain response to the outcomes. When their trust resulted in a fair split, their brains processed it with high emotional significance. When they were betrayed, the deviation between what they expected and what they received triggered a massive electrical response.

Psychopathic traits are consistently linked to a high sensitivity to rewards. People with these traits are heavily driven by the prospect of gaining an advantage. The brain data reflects this sensitivity, indicating that they experience the disappointment of a missed payout far more acutely than the average person.

The authors noted a few limitations to the experiment. The sample size of 44 individuals was relatively small, and the participants were all healthy college students rather than individuals with clinical psychopathy diagnoses. The results represent subclinical variations in personality rather than severe psychiatric conditions.

Future studies will need to expand the participant pool to see if these patterns hold up in broader demographics. Researchers also hope to separate the specific facets of psychopathy, such as antisocial lifestyle factors versus emotional deficits, to see how each distinct element influences the choice to collaborate with others.

The study, “How psychopathic traits affect individuals’ trust decisions and outcome evaluations: preliminary ERP evidence,” was authored by Fengbo Guo, Xiuying Zheng, Leru Zhong, Li Gu, and Xiuling Liang.