WHEN we speak of "images" in connection with Imagination and Recognition we do not refer merely to mental pictures of things seen. Mental images are representations of past mental experiences of any and every kind. They include past sensations of sound, taste, smell, feeling, pain, motion and the other senses, as well as sensations of sight. One may have a mental image of the voice of a friend, of the perfume of a flower, just as he may have mental images of their appearance to the eye. Indeed, the term "image" is perhaps unfortunately used in this way, since it must be made to include not only mental pictures in a visual sense, but all forms of reproductive mental activity.

Our recollection of past experiences may be either full and distinct or hazy and inadequate. Some persons are entirely unable to reproduce certain kinds of sensory experiences. Somehow they are aware of having had these experiences, but they cannot reproduce them. Every one of us has his own peculiarities.

This morning I called upon a friend in his office. I was there but a short time. Yet I can easily call to mind every detail of the surroundings. I can see the exterior of the building, its form, size, color, window-boxes with flowers, red tile roof, formal gardens in the open court, and even many of the neighboring buildings. I can plainly recall the color of the carpet on his office floor, the general tone of the paper on the wall, the size, type and material of his desk, and many other elements going to make up an almost perfect mental duplicate of the scene itself. I can even see my friend sitting at his desk, and can distinctly remember the color, cut and texture of his clothing and just how he looked when he smiled.

Last evening we entertained a number of friends at dinner. One of the ladies was an accomplished musician, and later in the evening she delighted us with her exquisite playing upon the piano. The airs she played were familiar to me. I am fond of music and I enjoyed her playing. I can sit here today and in imagination I can see her seated before the piano and remember just how her hands looked as she fingered the keys. But I find it difficult to recall the air of the selection or the tones of the piano. My mental images of the notes as they came from the piano are faint and uncertain and not nearly so distinct and clear as my recollection of the scene.

I find it easy to recall the appearance of the food that was served me for breakfast this morning. I can also faintly imagine the odor and taste of the coffee and toast, but I find that these images of taste and smell are not nearly so realistic as my mental images of what I saw and heard during the course of the meal.

When I was in college I was very fond of handball and was a member of the handball team. It has been many years since I played the game, yet I can distinctly feel the peculiar tension of the right arm and shoulder muscles that accompanied the "service." Nor do I feel the slightest difficulty in evoking a distinct mental image of the prickly sensations that so annoyed me as a boy when I would first put on woolen underwear in the fall of the year.

From these examples, it is apparent that we can form mental images of past sensations of sight, sound, taste, smell and feeling, and indeed of every kind, including the muscular or motor sense and the sense of heat and cold.

But there is the greatest possible difference in individuals in this respect. Some persons have distinct images of things they have seen, are good visual-izers. Others are weak in this respect, but have clear auditory images. And so as to all the various kinds of sensory images.

This is a fact of comparatively recent discovery. The first proponent of the idea was Fechner, but no statistical work was done in this line until Gal-ton entered the field, in 1880. In his "Inquiries into Human Faculties," he says:

"To my astonishment, I found that the great majority of the men of science to whom I first applied protested that mental imagery was unknown to them, and they looked on me as fanciful and fantastic in supposing that the words 'mental imagery' really expressed what I believed everybody supposed them to mean. They had no more notion of its true nature than a color-blind man, who has not discerned his defect, has of the nature of color. They had a mental deficiency of which they were unaware and naturally enough supposed that those who affirmed they possessed it were romancing."

The investigations of Dr. Galton were continued by Professor James, of Harvard University. He collected from hundreds of persons descriptions of their own mental images. The following are extracts from two cases of distinctly different types. The one who is a good visualizer says:

"This morning's breakfast-table is both dim and bright; it is dim if I try to think of it with my eyes closed. All the objects are clear at once, yet when I confine my attention to any one object it becomes far more distinct. I have more power to recall color than any other one thing; if, for example, I were to recall a plate decorated with flowers I could reproduce in a drawing the exact tone, etc. The color of anything that was on the table is perfectly vivid.