Researchers from the Netherlands have uncovered new insights into the emotional processing deficits in psychopathic individuals. The study, published in the Journal of Psychiatric Research, reveals that psychopathic patients exhibit significantly weaker short-latency facial muscle responses to happy expressions compared to non-psychopathic individuals. This impairment in mimicking emotional facial expressions may contribute to the well-documented empathy deficits observed in psychopathy, suggesting a potential biomarker for this personality disorder.
Psychopathy, a personality disorder characterized by a lack of affective empathy, poses significant challenges in both diagnosis and treatment. Given its association with a substantial proportion of violent crimes, understanding the roots of these empathy deficits is critical for developing effective interventions. One promising area of investigation is emotional mimicry, the automatic imitation of another person’s facial expressions, which is believed to play a foundational role in the empathy process.
Emotional mimicry is an essential component of human social interaction, facilitating emotional resonance and understanding between individuals. Previous research has suggested that deficits in emotional mimicry may be linked to empathy impairments in psychopathy. By studying the facial mimicry responses to emotional expressions, the researchers aimed to uncover specific deficits in the automatic processing of emotional cues among psychopathic individuals.
The study involved 24 male psychopathic patients and 21 male non-psychopathic controls, all from high-security forensic psychiatric hospitals in the Netherlands. The psychopathic patients were diagnosed using the Psychopathy Checklist-Revised, a widely accepted diagnostic tool for assessing psychopathy. Participants were required to be in good physical health, between 18 and 60 years old, and have a minimum IQ of 80.
Participants were shown dynamic morphed pictures of happy and angry facial expressions while their facial muscle activity was recorded using electromyography (EMG). This technique measures muscle responses by detecting electrical activity, providing insights into the participants’ facial mimicry responses. The EMG recordings focused on two facial muscles: the zygomaticus major, which is responsible for smiling, and the corrugator supercilii, responsible for frowning.
The study followed a within-subject, double-blind, counterbalanced, cross-over design for the psychopathic patients. Each patient participated in two sessions, receiving either a dose of oxytocin or a placebo in the form of a nasal spray. The control group, however, did not receive any treatment and was tested in a single session.
The primary goal was to observe early facial mimicry responses within the first 600 milliseconds after exposure to the emotional stimuli. This period was chosen to capture the automatic, preconscious responses thought to be involved in emotional processing.
The study found significant differences in the facial mimicry responses between psychopathic patients and non-psychopathic controls. Specifically, psychopathic patients showed significantly weaker zygomaticus responses to happy faces compared to the control group. This difference was observed consistently within the first 600 milliseconds of exposure to the emotional stimuli, indicating a deficit in the automatic mimicry of positive emotional expressions.
The results for angry faces were less conclusive. While psychopathic patients exhibited weaker corrugator responses to angry faces, the difference did not reach statistical significance. This trend suggests that psychopathic individuals might also have impairments in processing negative emotions, but further research is needed to confirm this finding.
When examining the effects of oxytocin, the researchers found no significant differences in mimicry responses between the oxytocin and placebo conditions in the psychopathic patients. This result contradicted the hypothesis that oxytocin would enhance facial mimicry in psychopathic individuals. Although there was a trend toward stronger corrugator inhibition (i.e., relaxation) when viewing happy faces in the oxytocin condition, this difference was not statistically significant.
The study had some limitations that could be addressed in future research. First, the sample size was relatively small, which may limit the generalizability of the findings. Larger studies are needed to confirm these results. Additionally, the use of morphed facial expressions, which may appear less natural than real facial movements, could have influenced the participants’ mimicry responses. Future studies should consider using video recordings of natural facial expressions to assess mimicry more accurately.
“Notwithstanding these limitations, the current study provides several valuable insights into the relationship between psychopathy and facial mimicry,” the researchers concluded. “A unique point of this study is that we investigated a clinically identified and PCL-R confirmed group of forensic psychopathic patients who were not treated with medication like selective serotonin reuptake inhibitors, selective noradrenaline reuptake inhibitors, antipsychotics, or hormonal libido inhibitors. This study showed reduced mimicry of corrugator and zygomaticus of angry and happy expressions, respectively. This finding is consistent with the results obtained in a study with male adolescents with disruptive behavior disorders and high [conduct disorder] traits (van Boxtel et al., 2022), which leads us to posit a lifetime developmental deficit in short-latency mimicry in psychopathy…”
“Cleckley (1941) originally described the psychopath’s severe deficits in the behavioral, emotional, and interpersonal domains. He stated that psychopathic individuals have a ‘convincing mask of sanity’ and are unable to attribute genuine affective meaning to important experiences, despite their intact rational processes. Although further research is warranted, we assume that our study of short-latency facial mimicry has revealed some insight behind the masks of our group of psychopathic patients. One might also ask whether deficiencies in short-latency facial mimicry are a biomarker of psychopathy. EMG is an interesting parameter in that regard and we advocate future research on that application.”
The study, “Revealed masks: Facial mimicry after oxytocin administration in forensic psychopathic patients,” was authored by Ronald J.P. Rijnders, Anton van Boxtel, Minet de Wied, Jack van Honk, Maaike M. Kempes, and Peter A. Bos.
