Psychopaths: A Scientific Perspective

Charming and pathologically deceitful, heartless and irresponsible, dangerous and impulsive-these are the hallmarks of psychopaths. In his book, “A Reliable Account of People Without Pity, Conscience, or Remorse,” Dr. Kent Kiehl, professor at the University of New Mexico and an expert in psychology, neuroscience, and law, shares his extensive research on psychopaths. His work spans from studying ruthless killers behind bars to identifying early warning signs of callousness and indifference in children.

Dr. Kiehl has interviewed thousands of inmates, diagnosed hundreds of psychopaths, and traveled to prisons across the United States with a mobile brain scanner to study the minds of individuals who continue to puzzle scientists. Through his personal story and the latest scientific findings, Dr. Kiehl offers readers a glimpse into the fascinating yet still mysterious world of the psychopathic mind. This book is invaluable for anyone seeking a scientific understanding of psychopathy.

Diagnosing Psychopathy: The Hare Psychopathy Checklist

To diagnose psychopathy in prisons, Dr. Kiehl used the Hare Psychopathy Checklist, which includes the following criteria:

• Glibness/superficial charm
• Grandiose sense of self-worth
• Need for stimulation/proneness to boredom
• Pathological lying
• Conning/manipulativeness
• Lack of remorse or guilt
• Shallow affect
• Callousness/lack of empathy
• Parasitic lifestyle
• Poor behavioral controls
• Promiscuous sexual behavior
• Early behavioral problems
• Lack of realistic long-term goals
• Impulsivity
• Irresponsibility
• Failure to accept responsibility for own actions
• Many short-term marital relationships
• Juvenile delinquency
• Revocation of conditional release
• Criminal versatility

Exploring the Psychopathic Brain

After diagnosing psychopathy, Dr. Kiehl began studying the brain waves of psychopaths using EEG, a method commonly used to assess various clinical disorders. He focused on event-related potentials, particularly the third positive peak-P300-since most mental disorders show changes in this peak. Dr. Kiehl hypothesized that deviations in the P300 would indicate differences between the brains of psychopaths and non-psychopaths. His research found significant differences in this peak in 97% of the psychopaths studied. Further investigation revealed that patients with damage to the medial and lateral temporal lobes exhibited similar brain responses to those of psychopaths.

Subsequent studies aimed to determine whether psychopaths have abnormalities in the medial and lateral temporal lobes, which include the amygdala, hippocampus, and temporal pole (anterior superior temporal gyrus). The amygdala plays a crucial role in memory, decision-making, and emotional responses, especially in amplifying significant information and directing attention to important stimuli. For example, if you hear a loud noise in a crowded street and quickly turn to find the source, your amygdala has heightened your awareness and triggered a mild fear response.

The hippocampus manages complex short-term memory processes and transfers processed information into long-term memory. All our professional knowledge, childhood memories, and information about significant life events and familiar faces are stored thanks to the hippocampus, which also governs emotional memory. This brain region continues to grow throughout life, becoming thicker with age, and is especially adept at storing emotional memories. The amygdala and hippocampus are classic members of the limbic system, which regulates affective and emotional processes. The temporal pole, part of the heteromodal associative cortex, integrates sensory information.

Emotional Memory Testing

One of Dr. Kiehl’s favorite tests, developed from his team’s pilot studies, is the emotional memory paradigm. In this test, participants are asked to memorize a list of twelve words presented one by one on a screen. After a 20-second rehearsal phase, they are tested by being shown twelve words again-half from the original list and half new. Participants indicate whether each word was on the previous list. Over 15 minutes, about 20 new lists are presented. Unbeknownst to the participants, the lists contain both neutral (e.g., table, chair, leg) and emotional (e.g., hate, kill, death) words. Dr. Kiehl found that typical individuals recall emotional words better than neutral ones, and that the amygdala and anterior and posterior cingulate cortex are more active when processing emotional words.

Brain Anatomy and fMRI Studies

To study the anatomy of the psychopathic brain, Dr. Kiehl used advanced MRI technology. The most common method involves a modified MRI system that measures changes in brain blood flow using labeled oxygen. Like muscles, brain neurons need oxygen to function. Oxygen binds to hemoglobin in the lungs, and the circulatory system delivers oxygen-rich blood to the brain. MRI can distinguish between oxygen-rich and oxygen-poor blood, allowing researchers to capture precise images of brain regions consuming oxygen during various tasks. This is known as functional magnetic resonance imaging, or fMRI.

fMRI studies of psychopaths revealed that the amygdala and anterior and posterior cingulate cortex were highlighted in blue-indicating they are less active in psychopaths than in typical individuals. These brain regions are part of the paralimbic system. Dr. Kiehl developed the paralimbic dysfunction model of psychopathy, noting that patients with paralimbic system injuries, like criminal psychopaths, struggle to recognize vocal intonations or facial expressions, have difficulty controlling behavior, making decisions, restraining themselves, avoiding harmful situations, and often display apathy, disorganized relationships, defiance, disregard for social norms, and lack of respect for authority. Interestingly, patients with paralimbic system damage sometimes also experience nighttime enuresis (bedwetting), one of the signs in the Macdonald triad.

Structural Differences in the Psychopathic Brain

How else does the psychopathic brain differ from that of typical people? As people age, gray matter decreases in many brain regions, but in areas where memories are stored, density increases over time-the more memories, the higher the density. In psychopaths, studies have found reduced gray matter density in the orbitofrontal cortex, amygdala, hippocampus, insula, temporal pole, and anterior and posterior cingulate cortex. Reduced gray matter density in the paralimbic system may indicate atrophy, suggesting these brain areas are underused throughout life. Studies of incarcerated adolescent psychopaths confirmed Dr. Kiehl’s hypothesis that paralimbic system atrophy is present from birth in psychopaths.

Of course, the psychopathic brain still holds many secrets, and much research remains to be done. But thanks to dedicated scientists like Dr. Kent Kiehl, the veil of mystery is gradually being lifted.