MENTAL IMAGERY. 



73 



tliough correct in its operations, the associations will be few, and the 

 generalized image based on insufficient data. If the visualizing power 

 be faint, the generalized image will be indistinct.* 



Some persons have the power of combining in a single perception 

 more than can be seen at any one moment by the two eyes. It is 

 needless to insist on the fact that all who have two eyes see stereo- 

 scopically, and therefore somewhat round a corner. Children, who can 

 focus their eyes on very near objects, must be able to comprise in a 

 single mental image much more than a half of any small thing they 

 are examining. Animals such as hares, whose eyes are set more on 

 the side of the head than ours, must be able to perceive at one and the 

 same instant more of a panorama than we can. I find that a few per- 

 sons can, by what they often describe as a kind of touch-sight, visual- 

 ize at the same moment all round the image of a solid body. Many 

 can do so nearly, but not altogether, round that of a terrestrial globe. 

 An eminent mineralogist assures me that he is able to imagine simul- 

 taneously all the sides of a crystal with which he is familiar. I may 

 be allowed to quote my own faculty in this respect. It is exercised 

 only occasionally and in dreams, but under those circumstances I am 

 perfectly conscious of embracing an entire sphere in a single per- 

 ception. 



This power of comprehension is practically attained in many cases 

 by indirect methods. It is a common feat to take in the whole sur- 

 roundings of an imagined room with such a rapid mental sweep as to 

 leave some doubt whether it has not been viewed simultaneously. Some 

 persons have the habit of viewing objects as though they were partly 

 transparent ; thus they can see the north and south poles of a globe, 

 but not the equatorial parts, at the same time. They can also see into 

 all the rooms of an imaginary house by a single mental glance. A 

 fourth class of persons have the habit of recalling scenes, not from the 

 point of view whence they were observed, but from a distance, and 

 they visualize their own selves as actors on the mental stage. By one 

 or other of these ways, the power of seeing the whole of an object, and 

 not merely one aspect of it, is attained by many persons, and might 

 probably be attained by all. 



A useful faculty, easily developed by practice, is that of retaining 

 a mere retinal picture. A scene is flashed upon the eye ; the memory 

 of it persists, and details which escaped observation during the brief 

 time when it was actually seen may be analyzed and studied at leisure 

 in the subsequent vision. 



The place where the image appears to lie differs much in different 

 persons. Most see it in an indefinable sort of way, others see it in 

 front of the eye, others at a distance corresponding to reality. There 

 exists a power which is rare naturally, but can, I believe, be easily 



* It may possibly interest some persons, in connection with this topic, to refer to my 

 " Psychometric Facts," in the " Topular Science Monthly" for April, 1879. 



