Tonic Immobility

Tonic Immobility refers to a person's performance in high stress situations.  It is when a person freezes during a dangerous situation and cannot escape from the threatening danger at hand.  In just the first chapter when Macklin and Wild were sent back into the ship to retrieve supplies, Macklin took in the dangers around him and froze.  Had Wild not been there to step up and enter the small space to pass supplies to Macklin, who knows what Macklin's fate would have been.  It is strange to me that a person's survival instincts do no kick in, rather than merely freezing in the middle of a dangerous situation.  The lecture slides specifically say that freezing is a survival instinct in animals because their predators do not attack non moving creatures.  This fight or flight response seems a bit primitive for humans to experience when it comes to a life or death situation.  Another question that comes to mind is whether or not the definition of tonic immobility can be related to instances that are not life or death; for instance, if someone freezes during an audition or test is it considered tonic immobility or not since it is not a dangerous situation?