“You must realize that fear is not real. It is a product of thoughts you create. Do not misunderstand me. Danger is very real. But fear is a choice.”

― Will Smith as General Cypher Raige in After Earth

Just in time for Father’s Day weekend, the father-and-son duo Will and Jaden Smith costar in the new filial love epic/sci-fi adventure After Earth. Stranded in post-human Earth after a crash landing, father and son must survive injuries, a poisonous planet, and the attack of a monstrous alien life form known as “Ursa”. Ursas are blind and deaf, but can locate prey by smelling their fear. The solution: don’t be afraid of Ursas, and they won’t be able to “see” you (a technique called “ghosting”). The problem: Ursas are really terrifying. Ranger General Cypher Raige excels at ghosting, but teenage son and failed ranger Kitai Raige is not quite there yet. The movie is predictable yet enjoyable, and in my opinion far better than you’d expect after reading some of the reviews from opening weekend.

The neuroscience connection was intriguing too: to what extent is fear hardwired in the brain? Behavioral therapies can successfully eliminate or reduce phobias to specific items or situations, but can one suppress fear in general? Unlike Cypher Raige, most of us appear to have limited control over our fear.

Could Cypher Raige’s fearlessness be the product of a neurological lesion? He reports in the movie that he discovered ghosting when he was dragged to the bottom of a river and injured by an Ursa. He made peace with his imminent death only to discover that the Ursa could at that moment no longer see him, and swam away. Well, one distinct possibility is that Raige’s amygdala --a brain structure directly related to the perception of fear--, was damaged in the struggle. Too bad he didn’t realize he had a brain injury: all of the human warriors could have had immediate neurosurgery to resect their amygdalas, and win the war in no time!

Scientific evidence supports this idea. A woman known as SM suffered damage to her amygdala as a teenager, which then obliterated her fear. She later experienced some highly dangerous situations in her life, such as being held at knifepoint, but met them with perfect fearlessness. Sounds like pretty good Ranger material, doesn’t she? Not so fast. In a study published in Nature Neuroscience earlier this year, neuroscientist John Wemmie and his colleagues were able to produce panic responses in SM and two other patients (also unable to experience fear due to amygdala lesions). They had the patients inhale 35% carbon dioxide, which “stimulates breathing and can provoke both air hunger and fear”. All three patients had panic attacks triggered internally by CO2, despite their lack of fear responses to external stimuli and events. So amygdalas may not be critical to all fear, but play a role in reacting to external danger only.

The research also suggests that, contrary to Cypher Raige's assertion, fear may not be a choice after all -- even for the most fearless humans we know.