Roses Don't Smell as Sweet to Psychopaths

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By most accounts, Ted Bundy was handsome, charming, and intelligent. He was also violent, manipulative, amoral—and exhibited many of the hallmarks of a psychopath. Psychologists use an extensive list of traits to identify psychopaths, and now they have one more marker that might diagnose them: a recent study suggests that psychopaths possess a poor sense of smell.

Psychopathy is usually diagnosed using the Hare Psychopathy Checklist - Revised, which analyzes at least 20 different aspects of someone's personality and case history to determine if that person has the disorder. Psychopaths are typically callous, insincere, impulsive and pleasure-seeking. Past research has found that those afflicted show lessened functioning in the orbitofrontal cortex in the front of the brain, an area that controls planning, controlling impulses, and following norms.

Smells Like Psychopathy

In addition to controlling those behaviors, the orbitofrontal cortex aids olfactory sensing—so Mehmet Mahmut and Richard Stevenson of Australia's Macquarie University decided to test 79 non-criminal adult psychopaths' senses of smell. First, the researchers measured levels of psychopathic behavior based on four traits: manipulation, callousness, erratic lifestyles, and criminal tendencies. They also looked at how much each participant could exhibit empathy. Then Mahmut and Stevenson tested each person’s olfactory abilities.

They found that those who showed the highest levels of psychopathic behavior failed to identify smells and could not discern the difference between two smells. The researchers believe that understanding that psychopaths have lessened smelling ability can provide scientists with another way to diagnose the disorder—which can be a challenge, because psychopaths are often excellent actors.

"Our findings provide support for the premise that deficits in the front part of the brain may be a characteristic of non-criminal psychopaths," Mahmut and Stevenson write in the paper, which appears in the journal Chemosensory Perception. "Olfactory measures represent a potentially interesting marker for psychopathic traits, because performance expectancies are unclear in odor tests and may therefore be less susceptible to attempts to fake good or bad responses."