New research published in Biological Psychology explores the relationship between psychopathic fearlessness and low defensive cardiac reactivity. According to the new findings, women with high scores in the psychopathic trait of fearlessness tend to exhibit reduced heart rate changes when faced with an intense and unexpected stimulus. But this relationship was not found among men.
Previous research has found that people with certain psychopathic traits often have less of an automatic startle response to threats. This has been linked to the trait fearlessness part of psychopathy.
Beyond just the startle response, other physiological measures have also been linked to psychopathy, like reduced muscle tension and lower heart rate in certain situations. There’s even been work to combine these various measures into an index of “threat sensitivity,” which could serve as a way to quantify and study these traits further.
The new angle in this study is looking at what’s called the Cardiac Defense Response (CDR). This is a complex pattern of changes in heart rate that happens in response to a sudden, unexpected threat or shock. CDR, reflected in changes in heart rate and other cardiovascular parameters, is believed to represent the activation of the sympathetic branch of the autonomic nervous system, the component involved in triggering ‘fight or flight’ responses to perceived threats.
The researchers hypothesized that the CDR might be a useful new measure to study the fearlessness trait in psychopathy. They were particularly interested in the second acceleration phase of the CDR, because it seems to be associated with readiness to respond to threats.
The research enlisted 156 participants (60 men), who completed the Psychopathic Personality Inventory-Revised (PPI-R), a self-reported measure of psychopathic tendencies. This questionnaire looks at a range of traits such as social influence, stress immunity, fearlessness, Machiavellian egocentricity, rebellious nonconformity, blame externalization, carefree nonplanfulness, and coldheartedness.
A defense psychophysiological test measuring CDR was administered in which the participants were subjected to an unexpected, intense white noise stimulus after an 8-minute resting period. They were told they were participating in a study to record their electrocardiogram under resting conditions, without mention of the upcoming noise. Their heart rates were recorded from 15 seconds before the stimulus onset to 80 seconds after.
The study found that men outscored women in nearly all aspects of psychopathy. Additionally, men tended to have a higher heart rate changes (both increases and decreases) in response to the loud noise than women did. This was especially true between certain time points after the noise was played.
The heart rate response to the loud noise was linked to some of the personality traits measured by the PPI-R questionnaire. Specifically, women who scored high in ‘fearless dominance’ (which is made up of traits like social influence, stress immunity, and fearlessness) showed a lower average heart rate change in response to the loud noise.
Looking more closely at the components of the ‘fearless dominance’ factor, it was found that women who scored higher on the ‘fearlessness’ trait specifically showed a lesser heart rate increase during the ‘second acceleration’ phase of the defense response (where the heart rate goes up after initially slowing down, a process related to preparing the body to respond to the threat). This remained true even when controlling for the influence of the other traits in the fearless dominance factor.
This finding is significant because it shows a gender-specific link between fear-related traits and the body’s defense responses. It suggests that the heart’s response to threat could be a useful way to study fearlessness as it appears in psychopathy, and to understand how this might differ between men and women.
The research team acknowledged a few limitations; first, the study used a self-report measure of psychopathy, which may be subject to bias and may not accurately capture all aspects of psychopathy. Additionally, the study used a relatively small sample size, which may limit the generalizability of the findings. Finally, the study did not examine other potential factors that may influence the relationship between psychopathic fearlessness and CDR, such as childhood trauma or other environmental factors.
The study, “Low defensive cardiac reactivity as a physiological correlate of psychopathic fearlessness: Gender differences“, was authored by V. Branchadell, R. Poy, P. Segarra, P. Ribes- Guardiola, and J. Moltó.
