Paramnesia of this kind is known, according to the observations of Lalande,[218] to thirty people in a hundred, and Heymans found it in a considerable proportion of students of both sexes. Such estimates are probably too high if we take into consideration the general population. This experience seems, as Dugas and others have noted,[219] to affect educated people, and notably people of more than average intellect, who use their brains much, especially in artistic and emotional work, to a very much greater degree than the ignorant and phlegmatic manual worker.[220] Dickens has already been mentioned; many other notable writers have referred to this or some allied feeling, stating that they had experienced it, and Sir James Crichton-Browne brings forward a number of passages from the poets in evidence of their familiarity with such phenomena.[221] Shelley (who appears on at least two occasions to have experienced hallucinations also) underwent what may be regarded as an experience of paramnesia (described in his _Speculations on Metaphysics_) which is of interest in the present connection because it brings this phenomenon into relation with dreams. He was walking with a friend in the neighbourhood of Oxford, when he suddenly turned the corner of a country lane and saw 'a common scene' of a windmill, etc., which, it immediately seemed to him, he recollected having seen before in a dream of long ago. Five years afterwards he was so agitated in writing this down that he could not finish the account. The real resemblance of 'a common scene' with a similar dream scene, even supposing it could be recollected when the two experiences were separated by a long interval, would scarcely be a coincidence likely to cause agitation. The emotion aroused seems to mark the experience as belonging to the class of paramnesic illusions which so often make a peculiarly vivid impression on those to whom they occur.