A middle-aged woman known as SM blithely reaches for poisonous snakes, giggles in haunted houses and once, upon escaping the clutches of a knife-wielding man, didn’t run but calmly walked away. A rare kind of brain damage precludes her from experiencing fear of any sort, finds a study published online December 16 in Current Biology.
SM has an unusual genetic disorder called Urbach-Wiethe disease. In late childhood, this disease destroyed both sides of her amygdala, which is composed of two structures the shape and size of almonds, one on each side of the brain. Because of this brain damage, the woman knows no fear, the researchers found. . . .
Feinstein and his colleagues sifted through SM’s past, looking for instances when she should have been scared. SM said she never felt fear, even when threatened with a knife or a gun. The researchers gave SM an electronic diary that she carried for three months to record her emotional state. Fear didn’t make an appearance in the list of emotions. On a battery of questionnaires, SM wrote that she wasn’t afraid of public speaking, death, her heart beating too fast or being judged negatively in a social setting.
Which gives me another chance to note that public speaking regularly shows up in surveys as the thing Americans fear the most.