Dissociation during trauma lacks an adequate definition. Using data obtained from interviews with 36 posttraumatic individuals conducted according to the phenomenological approach, this paper seeks to improve our understanding of this phenomenon. In particular, it suggesting a trade off model depicting the balance between the sense of agency and the sense of ownership : a reciprocal relationship appears to exist between these two, and in order to enable control of the body during trauma the sense of ownership must decrease. When (...) the relationship between the sense of agency and sense of ownership changes disproportionately to the constraints of the traumatic event, the dissociative mechanism becomes dysfunctional. By contrast, when the relations alter in accordance with the surrounding conditions, the dissociative mechanism functions properly. (shrink)