New electromyography research has found that individuals with more pronounced dark personality traits, primarily psychopathy and sadism, tend to have blunted startle responses. In other words, these individuals are less easily startled. The study was published in Scientific Reports.
The startle response is a natural and involuntary physiological reaction to a sudden and unexpected stimulus, characterized by a rapid, automatic, and exaggerated response. It typically includes physical reactions like jerking, jumping, a heightened state of alertness, increased heart rate, and muscle tensing. This response prepares the body to react swiftly to potential threats. It can vary in intensity depending on the individual and the nature of the stimulus.
In laboratory studies, the startle response is typically measured by monitoring the movements of the muscle surrounding the orbit of the eye. In general, this response is enhanced while participants are experiencing negative emotions (e.g., disgust, fear, sadness). This is referred to as aversive startle potentiation.
Previous research indicates that individuals with post-traumatic stress disorder exhibit heightened startle reactivity in both safe and dangerous situations. Conversely, repeat offenders and those with significant psychopathic tendencies display subdued startle reactions. Furthermore, the aversive startle potentiation is less intense in callous individuals who have a shallow emotional range and often manipulate or exploit others.
Study author Erin E. Buckels and her colleagues wanted to examine the association between startle reactivity and a cluster of personality traits known as the Dark Tetrad. The Dark Tetrad comprises four malevolent personality traits: narcissism, Machiavellianism, psychopathy, and sadism. These personality traits make individuals prone to manipulative and harmful behaviors towards others.
Narcissism involves an excessive focus on oneself and a lack of empathy for others. Machiavellianism is characterized by proneness to manipulation and the use of cunning to achieve personal goals. Psychopathy entails a lack of remorse and a tendency toward antisocial behavior, while sadism involves deriving pleasure from inflicting pain or suffering on others. These traits are often studied together due to their shared potential for causing harm and distress to others.
In the first study, 160 undergraduate students underwent various assessments, including those for anxiety, motivation, intolerance of uncertainty, self-reported startle tendencies, dark tetrad personality traits, and subclinical sadism. The researchers also examined participants’ startle responses using electrodes placed over the orbicularis oculi muscle beneath the right eye and provoked the response using sudden air puffs and bursts of loud white noise.
A subsequent study evaluated the correlation between different measures of startle reactivity, such as general reactivity, self-reported reactivity, and aversive startle potentiation, against personality assessments. The participants comprised 152 students and 92 individuals selected based on their extreme scores on sadism measures. They completed evaluations of maladaptive traits, psychopathy, dark tetrad personality characteristics, sadism, and self-reported startle reactions.
The second study had a more intricate startle testing approach. To gauge the enhancement of the startle reflex during sad emotions, participants viewed images categorized into positive, neutral, and negative emotional blocks, in addition to experiencing sudden loud noises.
The initial study’s findings revealed that participants with more distinct sadistic traits exhibited weaker startle reactions. Women, as well as those with heightened intolerance of uncertainty and stronger behavioral inhibition systems, had more pronounced startle responses. The subsequent study’s findings echoed these results but also indicated that individuals with heightened dark personality traits displayed generally muted startle reactions.
“We conclude that individuals with high levels of sadism show a diminished startle reflex that is relatively immune to potentiation by negative environmental stimuli,” the study authors wrote. “These findings provide further insight into the biological markers of the Dark Tetrad traits and their unique facets. Our findings may also have implications for fields beyond psychology, like business and economics, where managerial effectiveness (e.g., navigating workplace crises) and financial decision-making (e.g., loss aversion and risk-taking) may depend on the personality of a single individual with socially aversive tendencies.”
The study makes an important contribution to the scientific understanding of biological markers of dark traits. However, it also has limitations that need to be taken into account. Notably, most of the study participants were students. Although the second study included participants with very high levels of sadism, it is still unlikely that it included many individuals with truly high levels of this malevolent trait.
The study, “Blunted startle reactivity in everyday sadism and psychopathy”, was authored by Erin E. Buckels, Douglas A. Williams, Paul D.Trapnell, Siavash Kermani Koosheh, Owen M. Javra , and Sasha C. Svenne.
