DISSOCIATION (in psychology). In certain pathological conditions the normal nexus of relations which pervades the consciousness of an individual undergoes a profound altera tion, and for all that memory can do, a portion of the experience becomes a sort of enclave, cut off from its associates by boundaries bar ring out all recollection. Such a portion of experience is said to be dissociated from its companion states. As is indicated in the article PERSONALITY, DISORDERS OF, the nature of a dissociated portion of experience may vary be tween wide limits. It may be a longitudinal splinter, consisting of the stimuli received by an anaesthetic limb and the volition expressed thereby, or a stratum in practically undisputed sway of the individual over a given period of time, or as is very frequently the case, it may both coexist and alternate with the primary con dition. Furthermore, the primary and secondary conditions may or may not be of equal com pleteness and of equally sharp outlines. One condition is likely to have a certain degree of insight into the experiences of the other.
The physiological basis and psychological sig nificance of dissociation are alike matters of the greatest interest. It has been asserted by Sidis and other writers that the physiological basis of multiple personality is a change in the con ductivity of the interconnections between the neurons. A theory of this sort, however con
venient it may be as a means of summarizing the known phenomena, is worthless for explanatory purposes because of our profound ignorance of the processes of nerve-conduction and because of the practical impossibility of studying the anatomy of the intertwining of the dendrites of different neurons, except as mass-phenomena. The psychological significance of dissociation depends on whether the self as the unity of con sciousness is or is not something superadded to the system of experiences it unites. If the self is not something beyond the system it states, it follows that the result of a complete dissocia tion is the formation of two distinct selves, which, as Sidis puts it, share the same body in a manner analogous to the heads of a two headed monster. On the other hand, if the self is an entity entirety beyond its experiences, it becomespossible and even likely that the du of pa dissociated self is fictitious. See PERSONALITY, DISORDERS OF, and consult the bib liography there.