ix PSYCHO-PHYSICAL PHENOMENA 473 



perhaps be regarded as a partial suspension of the highest psycho- 

 physical processes, while the activity of the special centres, 

 particularly the visual and auditory, and of internal common 

 sensibility, is retained and even exaggerated. 



Dreams are more or less plainly conscious manifestations of 

 psychical activity during sleep. They result from a varied tissue 

 of images, representations, and evanescent ideas loosely and 

 irregularly woven together. The logical order is not infrequently 

 reversed in dreams ; associations which develop along collateral 

 and unexpected paths build up ideas by contiguity and similarity. 

 Even when the subject of the dream originates in an obscure 

 sensation of the real world, it is often so remote from it as to 

 make the psychical current absurd, incoherent, and chaotic. 

 Nevertheless we distinguish in dreams, when they are sufficiently 

 vivid, between the self and the not-self that is between what 

 can be referred to ourselves and what, really or by illusion, seems 

 to relate to the external world. So, too, in dreams the distinction 

 which is so clear in the waking state may persist between presenta- 

 tions and representations that is, between the images that seem to 

 be actual reality and the spurious or genuine memory images. 

 We may therefore with P. Janet consider dreams to be a different 

 orientation of the empirical personality " an allotropic state of 

 consciousness," or, in other words, a change of key in the mode 

 of cerebral activity. 



The methodical study of dreams presents many difficulties. 

 The objective phenomena of a dream may be reduced to a 

 minimum ; to a mild imitation of the thing one is dreaming 

 about, sometimes a word or sentence which gives a clue to the 

 subject of the dream, accompanied or not by more or less 

 elementary movements. In the rare cases in which dreams are 

 associated with complex, co-ordinated movements, and these pre- 

 dominate over words, somnambulism results, which is, as it were, 

 the staging and putting in action of the dream. 



Dreams, accordingly, can only be studied by the subjective 

 method i.e. by introspection with the inevitable twofold incon- 

 venience that the observer is simultaneously subject and object, 

 and that the matter for observation is not apprehended directly, 

 but only as a record, which is always confused and distorted. 



To lessen this inconvenience, Wundt advises that the dreamer 

 should force himself, directly he awakes, to retrace and fix as 

 firmly as possible the memory of the things dreamed about ; 

 should observe whether the momentary position of his body or 

 other circumstances can account for the initial causes or favour- 

 ing stimuli of the dream ; should, in fact, compare the predominat- 

 ing images of the dream with the impressions and records of the 

 day or of previous experience, whether recent or remote. 



The experiment has also been tried of determining dreams 



