People who score high on psychopathic traits are less likely to trust strangers and show distinct brain activity when evaluating social risks and economic rewards. Experiments using electroencephalographic recordings suggest that these individuals experience intense cognitive conflict when inhibiting cooperative behavior and feel great disappointment when their expectations for payment are violated. The study was published in the journal BMC Psychology.
While popular media often depicts psychopathy as a characteristic unique to violent criminals, psychologists recognize it as a continuous spectrum that exists in the general population. Characteristics of psychopaths include being manipulative, lacking empathy, selfishness, and impulsivity. Because these characteristics have a significant impact on how a person interacts with others, researchers frequently study how individuals at 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 party respects the trust, both parties can benefit. If the other party acts selfishly, the trustor may be disadvantaged. Understanding how the brain evaluates these outcomes provides a window into the biological mechanisms of human cooperation.
To observe this process, a research team led by Fengbo Guo from Guangdong Medical University in China designed an experiment using a trust game. The trust game is a classic tool in behavioral economics used to measure interpersonal trust and reciprocity.
The game mechanics are simple. The participant acting as the “trustor” receives the first amount of virtual money. They must decide whether to keep the money or transfer it to an anonymous “trustee.” If you keep it up, the round ends. When they transfer money, that amount is doubled and the trustee decides whether to split the larger pot equally or keep it all for themselves. Giving money shows trust, but keeping money shows distrust.
Researchers screened more than 300 healthy undergraduate students using a standard questionnaire designed to measure traits of subclinical psychopathy. From this wide range of participants, 44 participants were selected. Half of these individuals scored in the upper tier on psychopathic traits, while the other half scored in the lower tier.
Participants played 150 rounds of the Trust Game while connected to an electroencephalogram, a device that monitors electrical activity in the brain. Although participants were told that they were interacting with a human partner, the trustee’s responses were actually modified by a computer program. The game is designed in such a way that when you transfer funds, exactly half of the time you will get a fair share, and the other half of the time you will lose the entire amount.
Behaviorally, participants with high psychopathic traits chose to trust their partner much less often than participants with low psychopathic traits. The group high in psychopathic traits chose to share money about 53 percent of the time, compared to nearly 62 percent for the group low in psychopathic traits. This is consistent with past behavioral research showing that psychopathic traits are primarily egocentric and risk-averse in supportive environments.
When researchers looked at what happened immediately after participants experienced betrayal, an unpredictable pattern emerged. People low in psychopathic traits did not change their behavior after losing money. On the other hand, participants with high psychopathic traits chose to trust subsequent partners more often immediately after being betrayed.
The authors propose that people with heightened psychopathic traits may view gaming as a series of manipulative transactions. They may realize that the betrayal is statistically unlikely to continue, or they may try to recoup their losses by betting on future payouts.
EEG data collected during the decision-making stage provided clues about the mental effort required to make these choices. The researchers focused on a specific brainwave pattern called the N2 component. This electrical signal typically spikes in the fronto-central region of the brain about 200 to 350 milliseconds after a person senses conflict or exerts cognitive control.
For participants with high psychopathic traits, choosing not to trust a partner produced a much stronger negative N2 signal compared to choosing to trust. Participants with lower psychopathic traits showed no such electrical differences between their choices.
This suggests that people high in psychopathic traits experience intense cognitive friction when making uncooperative decisions. Humans generally recognize cooperation as a standard social norm. Researchers suggest that people with high levels of psychopathic traits fully understand this expectation, but make mental efforts to ignore their urge to conform to the norm in favor of securing immediate personal gain.
When participants learned that their trust had been confirmed or betrayed, their brains generated another set of unique signals. The researchers looked at brain waves associated with reward anticipation, which typically spike when the expected reward doesn’t materialize. Signals associated with this expectation are generated in brain regions responsible for evaluating wins and losses.
Participants with high psychopathic traits had significantly stronger brain responses to the results. When their trust resulted in a fair split, their brains processed it with emotional significance. When they were betrayed, the discrepancy between what they expected and what they received triggered a massive electrical reaction.
Psychopathic traits are consistently associated with higher sensitivity to reward. People with these traits are greatly driven by the prospect of gaining an advantage. Brain data reflects this sensitivity, showing that they feel the disappointment of missing a payment much more strongly than the average person.
The authors noted that this experiment had several limitations. The sample size was relatively small at 44 participants, and the participants were all healthy college students rather than people with clinically diagnosed psychopathology. This result represents an underlying personality fluctuation rather than a severe mental illness.
Future studies should expand the number of participants to see if these patterns hold true for broader demographics. Researchers also hope to isolate specific aspects of psychopathy, such as antisocial lifestyle factors and emotional deficiencies, to see how each different factor influences the choice to cooperate with others.
The study, “How psychopathic traits influence individuals’ trust decisions and outcome evaluations: Preliminary evidence for ERP,” was authored by Fengbo Guo, Xiuying Zheng, Leru Zhong, Li Gu, and Xiuling Liang.
