Buon giorno from Florence, where I’m presently under the Tuscan sun—sizzling like bacon, I should add—as a hive of awestruck, pale-legged American tourists wearing Nikes, cargo shorts and Polo shirts descend with digital cameras at the ready on the Renaissance city’s signature Duomo in the Piazza Della Signoria. As for me, I’m at an overpriced cafe with a “Coca-Cola Light” in my hand; in the square before me, a bedraggled carriage horse has its great tethered head to the ground, warily inspecting some lime-green gelato spilled moments ago on the cobblestones by a fussy little Australian boy. If I were of a literary rather than a scientific bent, I would find these scenes inspiring; Dante himself couldn’t imagine a stranger hell than his beloved Florence stuffed with such exotic modern characters, pigeons whiffling overhead. Instead, I’m gazing out across this piazza and wondering how many psychopaths there are milling about out there, the cleverest of whom often go unnoticed.

What prompts this strange thought is my earlier visit to a lesser-known tourist attraction here in Florence called “The Museum of Serial Killers.” After all, once one is finished marveling over masterpieces like Michaelangelo’s David and Botticelli’s Birth of Venus in the famed Galleria Dell’Accademia and the Uffizi, it’s easy to get fatigued by all the religious iconography in this city. I found myself standing before fantastic, gilded works by the Italian masters and muttering, “Just another Jesus,” and “Oh, it’s only Mary again.” (What a pity so many artists of that age concentrated their talents so heavily on so few subjects.) So, though it's sensational, The Museum of Serial Killers offers respite from these more venerable Florentine sites. Unfortunately, it’s also as tacky inside as its name on the marquee promises, mostly waxworks of notorious psychopaths such as the 15th century French sadist Gilles de Rais, a smiling and unctuous Ted Bundy leaning against a fancy sports car, even a disturbingly realistic reconstruction of John Wayne Gacy’s suburban living room—complete with decomposing corpses beneath the floorboards.

I confess, rather sheepishly, that the subject of serial killers has always held a certain dark allure for me. But I know I’m not alone. One person who shares my scholarly interest in serial killers, psychopaths and their unsettling ilk is an ironically personable young psychologist from Georgetown University named Abigail Marsh. I met Marsh last July at a very different latitude— on New Hampshire’s Squam Lake just a stone’s throw away from where the movie O n Golden Pond (1981) was filmed—during a Dartmouth-sponsored event called “Perceiving Other Minds.” She confided in me that her research interests may have something to do with the fact that she grew up in Tacoma, not far from Ted Bundy, the Green River Killer and the D.C. Sniper.

In her groundbreaking work funded by the National Institute of Mental Health, Marsh and her colleagues have been exploring how “callous and unemotional” individuals tend to show a very specific cognitive deficit: namely, they are especially poor at recognizing, processing and responding normally to the facial expression of fear on other people’s faces (a “normal” response being ceasing an assault on the frightened person or offering aid). Curiously, their trouble in this area is not due to a problem with facial expressions in general—they do perfectly well deciphering the look of disgust, anger, happiness and so on on other people’s faces. In contrast, autistics have trouble with pretty much all facial expressions of emotion, suggesting that, for them, this generalized difficulty is meaningfully linked to their broad social disfunction. Rather, it’s only the look of fear that puzzles diagnosably antisocial people (and to a somewhat lesser extent, sadness). Thus, in a converted boathouse on Squam Lake in early July, Marsh discussed several key studies, all indicating a fear-specific facial processing deficiency in children and adults with persistent antisocial behavioral tendencies. That is to say, “behavior that violates the rights and welfare of others or breaks important normative rules.”

To begin with, Marsh noted, ethologists have long-argued that the fear display evolved in humans and other animals as a “distress cue” signaling the absence or reduced threat of harm in the other party. In many respects, it is a more acute distress cue than sadness because it usually signals a more urgent need. Marsh believes it’s no accident that the expression of the human fear display designedly contorts the person’s face in a manner that gives it a particularly “neotonous” (babyish) appearance. Just as the cute, bubbly faces of infants and toddlers convey complete innocuousness and tend to emotionally disarm us of any hostile feelings toward them or elicit caregiving responses, the fear facial expression in adults possesses similar infantile physical characteristics, such as wide, rounded eyes and high brows.

In a 2008 article [PDF] in Neuroscience and Biobehavioral Reviews , Marsh and coauthor R. J. R. Blair argue that:


Distress cues such as fearful or sad expressions have been theorized to stabilize social interactions among healthy individuals by eliciting affective responses that reduce the likelihood of continued aggression against the victim. Such affective response may include empathy and remorse. Both of these responses are elicited by the perception and correct identification of distress cues such as fear expressions. That antisociality is associated with a lack of empathy and remorse ... supports the conclusion that antisocial individuals do not respond appropriately to distress cues.


Marsh relayed a chilling anecdote about a colleague of hers, University College London psychologist Essi Viding, who was going through a task with a psychopathic murderer in which a series of faces with different emotional expressions were laid out before the woman. When the murderer saw the picture of the fearful face, she scratched her head and said: “I don’t know what that expression is called, but I know it’s what people look like right before I stab them.”

It is important to emphasize that the difficulty these people have with the emotional expression of fear is due to a core neurological problem rather than a deliberate, selective inattention to fear. Specifically, functional MRI (fMRI) studies in both children and adults have revealed a telltale “hypoactivation” of the amygdala in response to fearful faces—essentially, this area of the brain fails to respond. In a recent study [PDF] in the American Journal of Psychiatry , Marsh and her colleagues exposed 36 children between the ages of 7-10 to a series of neutral, fearful and angry faces, which were projected onto a mirror while the children were in the MRI scanner. Using various assessment measures, such as “The Psychopathy Checklist” and the “Antisocial Process Screening Device,” twelve of the children had been clinically diagnosed as having “callous and unemotional” traits (antisocial). Another twelve had attention-deficit hyperactivity disorder (ADHD), and the remaining children served as “healthy” or normal controls.

To illustrate the behavioral profile of an antisocial child, the authors provide the following case study for one of these children, a 12-year-old boy referred to as “Mark” to protect his identity.


Mark is well-liked by his peers; he is confident and charismatic and is an entertaining storyteller. His popularity contrasts with the behavior he exhibits with his family and peers, however. With his parents, he is defiant, deceitful, or manipulative in order to achieve his desired outcomes. With siblings and peers, he tends toward verbal and physical intimidation. He engages in physical fights, shoplifts from stores, and engages in frequent fire-setting. He particularly likes fireworks; recently he set off several fireworks outside his school and videotaped the aftermath. His father states that Mark has never appeared to experience guilt or regret after engaging in these sorts of behaviors and that he seems to be “totally self-centered.”


As the researchers predicted for this study, the brain scans of the antisocial children—Mark and his eleven other callous and unemotional cohorts—showed significantly less amygdala activation in response to the image of the fearful face compared to the neutral one. In contrast, amygdala activity spiked in children with ADHD and the healthy controls when they saw the fearful face.

Like other personality traits, the degree to which one is “callous and unemotional” varies between individuals. And one doesn’t have to be a full-fledged psychopath to share some of the psychopath’s antisocial propensities. In fact, in a particularly clever set of experiments [PDF] published in a 2007 issue of the journal Emotion , Marsh and her colleagues Nalini Ambady and Megan Kozak showed that even in normal, nonclinical populations, the ability to detect fearful faces is correlated with people’s “prosocial” behaviors in a seemingly unrelated task. In other words, the better one is at identifying fearful faces (normal accuracy rates hover around 70 percent and are generally lower than for other emotional expressions), the kinder they are to strangers. In this study, identification accuracy of fearful faces predicted whether—and how much—the participants would donate money to a woman in need. Those who were better able to discriminate between fearful faces from other emotions also rated strangers as being more attractive when they thought the strangers would learn of others’ judgments of their appearance (compared to when they thought the images were simply stock photos from a catalogue).

A convincing look of fear is also difficult to feign. I asked my partner, Juan, to demonstrate and I’d swear he either just had a spontaneous orgasm or the milk in his latte had just gotten its revenge. (A scarier thought is that I just don’t have an eye for fearful faces.) In any event, I asked Marsh whether any work had been done on psychopaths’ actual production of the fear facial expression, given that it’s widely believed that compared to the rest of us, psychopaths are less fearful in general, insensitive to aversive events and high in risk-taking. I wanted to know whether these characteristics showed on their faces—or rather, failed to show. Marsh led me to some recent work by a team of German psychiatrists who analyzed the emotional responding of 25 psychopathic prisoners in response to positive and aversive stimuli. In contrast to another group of prisoners with Borderline Personality Disorder (BPD), the psychopaths showed significantly less facial expression in response to all of the stimuli (as measured by decreased electromyographic activity in the corrugator muscles), which the authors interpret as reflecting a pronounced lack of fear. Some showed no startle reflex at all to some rather unpleasant stimuli.

Ciao for now. I’m getting up to have a closer look at a young man on the other side of the piazza—he has the most curious look on his face ... I can’t quite make it out ...

In this column presented by Scientific American Mind magazine, research psychologist Jesse Bering of Queen's University Belfast ponders some of the more obscure aspects of everyday human behavior. Ever wonder why yawning is contagious, why we point with our index fingers instead of our thumbs or whether being breastfed as an infant influences your sexual preferences as an adult? Get a closer look at the latest data as “Bering in Mind” tackles these and other quirky questions about human nature. Sign up for the RSS feed or friend Dr. Bering on Facebook and never miss an installment again. For articles published prior to September 29, 2009, click here: older Bering in Mind columns.

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Editors' note 9/30/09: The second paragraph originally used the phrase "religious iconoclasm" in place of the correct term, "religious iconography." We regret the error.