To the average observer, it would seem that 44-year-old patient “SM” was just another typical mother of three: she scores normally on IQ tests, has good language skills and a decent memory. But, according to a paper by neurologists at the University of Iowa, SM is profoundly unusual. Because of a degenerative condition that left her with damage in certain brain structures, researchers say, SM is incapable of feeling fear.
The researchers know, because they spent several days trying to scare her silly. They exposed SM to snakes and spiders at a pet store, showed her clips of horror movies like The Shining and The Blair Witch Project, and took her through a haunted house in a former sanatorium. SM’s fear response? Nonexistent. (More on Time.com: Don’t Choke: 5 Tips for Performing Under Pressure)
In fact, she relished cuddling snakes and had to be stopped from reaching for a tarantula.
SM has a genetic condition that has disabled, in both hemispheres, a brain region known as the amygdala, which is involved in processing emotional memories and fear. She has been studied by neurologists for 20 years because her case is so extreme, and has so far been shown to be unable to read social situations that involve fear or to recognize evidence of fear on the faces of others.
SM says that she hasn’t felt afraid since a childhood incident involving a snarling Doberman pinscher. The research team — including Justin S. Feinstein, Ralph Adolphs, Antonio Damasio and Daniel Tranel — theorizes that her condition hadn’t yet destroyed her amygdala at the time. But what’s more interesting is her life experience since then, which has often been frightening and dangerous. Her lack of fear has many times caused her to place her own life in danger. The authors write in their case study, published on Dec. 16 by the medical journal Current Biology:
As it turned out, SM has encountered numerous events that would be considered fear-inducing or even traumatic in nature. For instance, she has been held up at knife point and at gun point, she was once physically accosted by a woman twice her size, she was nearly killed in an act of domestic violence, and on more than one occasion she has been explicitly threatened with death.
What stands out most is that, in many of these situations, SM’s life was in danger, yet her behavior lacked any sense of desperation or urgency. Police reports obtained from the local police department further corroborate SM’s recollection of these events and paint a picture of an individual who lives in a poverty-stricken area replete with crime, drugs, and danger. Of note, SM has never been convicted of any crime, but rather has been the victim of numerous crimes. Moreover, it is evident that SM has great difficulty detecting looming threats in her environment and learning to avoid dangerous situations, features of her behavior that have in all likelihood contributed to her high incidence of life-threatening encounters.
Take, for example, an anecdote reported by the Associated Press:
A man jumped up from a park bench, pressed a knife to her throat and hissed, “I’m going to cut you.”
SM, who heard a church choir practicing in the distance, looked coolly at him and replied, “If you’re going to kill me, you’re going to have to go through my God’s angels first.”
The man suddenly let her go. She didn’t run home. She walked.
“Her lack of fear may have freaked the guy out,” Feinstein said.
But it also got her into that situation in the first place, he noted. SM had willingly approached the man when he asked her to, even though it was late at night and she was alone, and even though she thought he looked “drugged out.”
The authors note that SM’s response to what would normally be considered fear-inducing situations was not characterized simply by a lack of responsiveness, but rather a heightened arousal and interest. In other words, she practically courted danger. (More on Time.com: How Retail Therapy Works: Spending Money for Social Acceptance)
Just as she felt curiosity instead of fear in the face of scary situations, so her memories of frightening experiences also diverged from the norm: when asked about her emotional response to such past incidents, she reported feeling angry, but didn’t show the enduring distress, panic and aversions that typically characterize survivors of similar violence.
These findings give researchers some hope that they can someday figure out how to stimulate the amygdala in survivors of violence to help prevent them from suffering post-traumatic stress disorder later on. (More on Time.com: Amnesia and a Camera: Photos as Memories)
The researchers stress that SM’s condition is more a curse than a blessing: “[SM's] behavior, time and time again, leads her back to the very situations she should be avoiding, highlighting the indispensable role that the amygdala plays in promoting survival by compelling the organism away from danger. Indeed, it appears that without the amygdala, the evolutionary value of fear is lost.”