Patients with extreme dissociative disorders remain in alternating psychophysiological states that appear separately, are discontinuous, and generally resist integrative tendencies. In this contribution, as an explanatory model, a comparison is made between an animal defensive reaction to life-threatening danger and a dissociative reaction of severely traumatized patients. Research data and clinical observations support the idea that there are similarities between `freezing' and concomitant development of analgesia in threatening situations in animals and humans.