MENTAL IMAGERY, 65 



of the nerves, as in dreams, in delirium, in high excitement, or under 

 the influence of certain drugs. 



These physiological considerations, vague as they are, will never- 

 theless suflice to establish the existence of a true kinship between men- 

 tal imagery and ordinary vision. They enable us to define Shakes- 

 peare's phrase of seeing " with the mind's eye " as a condition in which 

 the activity of the nervous center bears a higher ratio to that of the 

 nervous terminations than it does in actual sight. They also justify 

 us in ascribing the marked differences in the quality, as well as the 

 vividness, of the mental imagery of different persons, to the various 

 deo-rees in which the several links of a long nervous chain are apt to 

 be affected. 



The mental images of which I am about to speak are those which 

 are habitually suggested by well-known associations. Even when the 

 subject is thus limited, it is almost too large for the compass of a sin- 

 gle memoir. Therefore, I shall do my best at present not to encroach 

 upon that other very interesting branch of it, which treats of the vis- 

 ions and hallucinations that flash into view without any connection 

 with the subjects of conscious thought. It is my purpose to point out 

 the conditions under which mental imagery as above defined is most 

 useful, and the particular forms of it which we ought to aim at de- 

 veloping; and I shall adduce evidence to show that the visualizing 

 faculty admits of being educated, although no attempt has ever yet 

 been made, so far as I know, to bring it systematically and altogether 

 under control. 



I draw my conclusions from no small amount of testimony. In ad- 

 dition to a large quantity of oral information of which I have made 

 notes, I have received separate letters and replies by the hundred to a 

 long list of questions which I circulated, besides obtaining batches of 

 replies to the same questions from various schools. The answers, on 

 the whole, have been written in a style that testifies to much careful 

 self-analysis, and the general accordance of those that were, derived 

 from independent sources, together with the satisfactory way in which 

 I have found many of the statements to bear cross-examination, has 

 convinced me of their substantial truth. 



I find the distribution of the visualizing faculty, in respect to its 

 vividness, by a simple method I have described elsewhere.* I take a 

 haphazard bundle of returns, mark them as an examiner would mark 

 the papers of candidates, sort them in the order of their marks, and 

 clip them into a portfolio. If I open the book in the middle I read the 

 medium value ; if I open it at one quarter from the beginning I read 

 the highest quartile value ; if at one quarter from the end, the lowest 

 quartile. If I open it at one eighth of its thickness I read an octile 

 value ; and if at one sixteenth, a sub-octile. 



* See an article by myself in " Mind" (July, 1880), p. 301, on "Statistics of Mental 

 Imagery," and the references in the foot-notes to it. 



TOL. XTIII. 5 



