So if you could live without fear, would you?

Scientists got a glimpse of what that might be like in the 1930s working with monkeys. They cut out an area of the monkeys' brains called the temporal lobe. Before the surgery, the monkeys hid from experimenters, but afterwards they allowed people to pick them up.

Not only were the monkeys now fearless, they also displayed something called hypermetamorphosis. That's an irresistible urge to examine everything... cigarette stubs, food, wire cages, metal nuts...

In fact, when another animal attacked them, rather than run, the monkeys would approach the animal to examine it. You see, when the monkeys' temporal lobes were removed, so were the amygdala – a set of two almond-shaped structures responsible for processing emotions and fear.

What happens when humans lose their amygdalas? Since people with damage only to the amygdala are extremely rare, much of our knowledge about it came in the last twenty years from a woman known as S.M.

At age 20, she was diagnosed with a rare genetic disorder that damaged her amygdala. Today, S.M. is 44, with normal intelligence, language and perception. However, like the monkeys, she's a woman without fear.

Although S.M. can recall “hating” snakes in the past, she was now curious and fascinated. She held one, touched its tongue and, despite being told the larger snakes were dangerous, asked to touch them fifteen times.

S.M's story clearly illustrates the important role of the amygdala in human survival.

So, although Franklin Delano Roosevelt bolstered the nation by saying, “The only thing we have to fear is fear itself,” the inability to feel fear can be just as scary a thought.