The freeze response to threat is a passive response, during which the body can appear to be paralysed. In animals this can be a literal freezing of the whole body, but in humans it can be more complicated, such as going to a different place in the mind, such as dissociation. Freeze happens when fighting and fleeing don’t work and the threat is still there.
Much research on fight/flight/freeze has been carried out by Dr. Peter Levine. All animals are programmed by evolution to flee, fight, or freeze in the face of great threats to their survival. In humans, when these natural responses to danger are thwarted and people are helpless to prevent dangers to their survival, like in cases of a car accident or physical beating, the unfinished defensive actions become stuck as undischarged energy in their nervous systems. They stay physiologically frozen in an “unfinished” state of extremely high biological readiness to react to the traumatic event, even long after the event has passed. Levine believes that psychological trauma is very much about action interrupted, which the traumatised human brain and body still needs to complete processing. Often, people can experience traumatic events and process them without any long-lasting consequences. The problem occurs when the body and mind is unable to process the event or discharge the energy. The stress response is stuck and un-discharged. Levine explained in his 1997 book ‘Waking The Tiger, that this is ‘an incomplete physiological response suspended in fear.1’
1 Levine, P. A., & Frederick, A. (1997). Waking the tiger: Healing trauma – the innate capacity to transform overwhelming experiences. Berkeley, CA: North Atlantic Books,U.S.