The Motor Reaction in Attention
Attention is obviously a reaction of the individual to the stimulus that gets his attention; and it is in part a motor [{249}] reaction. The movements that occur in attending to an object are such as to afford a better view of it, or a better hearing of it, or, in general, such as to bring the sense organs to bear on it as efficiently as possible.
We may distinguish two sorts of motor reaction that occur in attention: the general attentive attitude, and the special adjustments of the sense organs. An audience absorbed in a speech or musical performance gives a good picture of the general attentive attitude. You notice that most people look fixedly towards the speaker, as if listening with their eyes, and that many of them lean forward as if it were important to get just as close as possible. All the little restless movements cease, so that you could "hear a pin drop", and at the tensest moments even the breath is checked. The attitude of attention is one of tense immobility, with the whole body oriented towards the object of attention. When the object of attention is something not present but thought of, a somewhat similar rigid attitude is assumed; the body is apt to lean forward, the neck to be held stiff, and the eyes to "stare at vacancy", i.e., to be fixed on some convenient object as a mere resting place, while attention is fixed outside the visual field altogether.
But we spoke of attention as mobile, and it would be strange if its mobility did not show itself in the motor reaction. It does in fact show itself in the sense organ adjustments which amount to exploratory reactions. Attention to an object in the hand is shown by "feeling of it", to a substance in the mouth by tasting movements, to an odor by sniffing movements, to a sound by cocking the head and turning the eyes towards the source of sound. The most instructive of this type of attention-reactions are those of the eyes. The eye is focused on the object that arouses attention, the lens being accommodated for its distance by the action of the little ciliary muscle inside the [{250}] eyeball; the two eyes are converged upon the object, so that the light from it strikes the fovea or best part of each retina; and the eyes are also turned up, down or sidewise, so as, again, to receive the light from the object upon the fovea.
This last class of eye movements is specially instructive and shows specially well the mobility of attention. Let a bright or moving object appear somewhere in the field of view--immediately the eyes turn towards it with a quick jump, fixate it for a few seconds and then jump elsewhere unless the object is found to be specially significant. Watch the eyes of one who is looking at a picture or scene of any sort, and you will see his eyes jumping hither and thither, as his attention shifts from one part of the scene to another. Ask him to abstain from this jumpy movement and let his eyes "sweep over" the scene, and he will confidently try to follow your instructions, but if you watch his eyes you will find them still jumping. In fact, "sweeping the glance" is a myth. It cannot be done. At least, there is only one case in which it can be done, and that is when there is a moving object to look at. Given an object moving at a moderate speed across the field of view, and the eyes can follow it and keep pace with it pretty accurately. But without the moving object as stimulus, the eyes can only execute the jump movement. There are thus two types of exploratory eye movement: the "jump" in passing from one object to another, and the "pursuit movement" in examining a moving object.
In reading, the eye moves by a series of short jumps from left to right along the first line of print, makes a long jump back to the beginning of the second line and another series of short jumps along that line, and so on. To appreciate the value of this jerky movement, we need to understand that each short jump occupies but a thirtieth to a fiftieth [{251}] of a second, while the "fixation pauses" between jumps last much longer, with the result that over ninety per cent. of the time spent on a line of print is fixation time, and less than ten per cent, is occupied in jumping from one fixation to the next. Now, it has been found that nothing of any consequence is seen during the eye jumps, and that the real seeing takes place only during the fixations. The jump movement, therefore, is simply a means of passing from one fixation to another with the least possible loss of time.
The eye sees an object distinctly only when at rest with respect to the object. If the object is still, the eye must be still to see it distinctly, and to see its different parts must fixate one after the other, jumping from one part to another. But if the object is in motion, the eye may still be able to see it distinctly by means of the pursuit movement, which is a sort of moving fixation.
The Shifting of Attention
Eye movement affords a good picture of the mobility of attention. Ordinarily the eye shifts frequently from one part of the field of view to another. When simply exploring a scene, it shifts about in what seems an indiscriminate way, though really following the principle of deserting each object as soon as it has been examined, and jumping to that other object which next has the advantage on account of movement, brightness, color, definite form, or habit of attention. In reading, however, the eye is governed by a definite interest, and moves consecutively along the series of words, instead of shifting irregularly about the page.
A moving object, or an object that is doing something, or even a complex object that presents a number of parts to be examined in turn, can hold the eye for some time. But it is almost impossible to hold the eye fixed for any length of time on a simple, motionless, unchanging object.