SM doesn’t feel fear. She has no phobias, no anxieties and is untroubled by life-threatening situations. This is not merely a case of a strong will able to suppress fear; for SM, the emotion simply doesn’t exist.
SM suffers from Urbach-Wiethe syndrome, a rare genetic disorder mainly affecting the skin and mucous membranes. It also causes damage to the amygdala, the region of the brain that generates fear. In SM’s case, it resulted in almost complete bilateral atrophy of the almond-shaped lobes (amygdala comes from the Greek amygdalē, almond).
Strangely, more than just an absence of fear, SM may also be drawn to danger. Despite claiming to dislike snakes and spiders, when confronted with them in a pet shop, she felt a desire to touch them.
Another group of rare disorders called congenital analgesias result in an inability to feel pain. Sufferers lack function in the nerves that detect pain, but are still able to feel pressure and temperature changes.
A life without fear or pain may sound desirable but these responses exist for sound evolutionary reasons. Congenital analgesia often results in a shortened life-span and an elevated risk for serious injury. Many mutilate their tongues and mouths by biting themselves during teething. Burns, bone fractures and accidental deaths are not uncommon. A Pakistani boy with the condition was found performing in a marketplace, piercing his arm repeatedly with daggers. He was dead by fourteen after jumping off the roof of a house.
Similarly, SM has found herself in an unusual number of life-threatening situations. She was once attacked with a knife by a drug addict she approached in a park one night. Perhaps perplexed by her abnormal response, the attacker let her go and SM calmly walked home.
These natural experiments demonstrate the value of fear and pain in helping us to avoid injury and death. Pain and fear are akin to the negative feedback of a Skinner box, teaching us through experience how to survive.
On the other hand, once in a threatening situation, few of us are able to think rationally because of the overwhelming nature of these emotions. In certain situations, an inability to feel fear or pain would be advantageous. An army of soldiers with congenital analgesia and Urbach-Wiethe syndrome might be a formidable weapon in battle.