Dissociation is a disconnection between a person's sensory experience, thoughts, sense of self, or personal history. People may feel a sense of unreality and lose their connection to time, place, and identity. An individual may feel disconnected from their body or feel that their surrounding environment is fuzzy and surreal.
The Freeze Response
When a traumatic event happens to us we can experience three different reactions: fight, flight, or freeze. Fight or flight is the hyper-arousal reaction. Our heart starts racing, we go to fight back, or we run away, we may experience panic attacks or intense anxiety.
The other way that a reaction to trauma can manifest is hypoarousal. This is the shutdown response, also known as the freeze response. When something traumatic happens to us, dissociation is the lack of reaction. We shut down, involuntarily, as survival mechanism. (Read more about this on my post about the Window of Tolerance)
Peter Levine discusses in his book, “Waking The Tiger”, (an excellent book on trauma) about the impala and the lion. One of the ways that the impala copes if he gets caught by a lion is by playing dead and disconnecting from it's body. This is a coping strategy so that if it starts to attacked by the lion, it doesn't have to physically feel the pain.