seen in all cases of expectation or expectant attention. The consequence of such pre-adjustment is, as has been proved by experiment, a shortening of the process by which sensations become distinct and are recognised. Here, as pointed out above, there is not only a preparatory muscular adjustment but a central psycho-physical preparation corresponding to the development of the idea of that which is expected.

This expectation may be of different degrees of perfection. Thus we may know (exactly or approximately) the time at which the sensation will occur. In listening to a new poem or a new musical composition we anticipate the succeeding sounds in their regular recurrence. This anticipation of a new impression (or series of impressions) after a regular interval is a condition of the easy apprehension and the agreeable effect of an orderly rhythmic sequence of sounds or sights. In such a case the mind not only adjusts itself to each new impression but has a prolonged or recurring satisfaction of nascent expectation.1

Expectation, in the full sense, involves some previous knowledge of the nature or quality of an impression, and not merely of the point of time of its occurrence. This again may be of various degrees of distinctness or completeness. I may, for example, have merely a vague anticipation of the words a person will utter on a particular occasion, e.g., in response to a toast. Such indefinite anticipation by effecting a preliminary peripheral and central adjustment (fixing of the head for hearing, sub-excitation of the auditory centre as a whole) may materially expedite the production of a clear impression. In other cases I may be able to distinctly forecast the particular sensation that is coming. Thus on watching a singer about to commence a familiar song I have an anticipatory idea of the opening tones. Such definite anticipation, by including a preliminary sub-excitation of the nerve-centre of the same kind as that produced by the particular sounds, will still further shorten the process of receiving a sensation. When this anticipation of the precise quality of an impression is supplemented by the prevision of the exact moment of its appearance, the preparation or pre-adjustment of attention may be said to be perfect.

1 Not all regular successions are equally favourable to adjustments. The attention adjusts itself to a moderately rapid sequence more easily than to a very rapid or a very slow one.

EXPERIMENTS ON ATTENTION.

155

§ 5a. Psychometrical Experiments on Attention. The measurement of the duration of the adjustive process in attention has been carried out by help of a series of experiments which belong to the new and promising department of experimental psychology, known as Psychometry. The method of experimentation consists in estimating by a delicate chronometric apparatus the interval between the reception of a sensory stimulus, say a sound, by the subject of the experiment, and the actual execution of a responsive movement, as of the hand or a particular finger. This interval is known as the "reaction-time". This period is supposed to be made up of a number of component periods, corresponding to the transmission of the nervous excitation from the peripheral organ to the brain, and so forth; and an attempt has been made by suitable variations of the experiment to measure the duration of each of these divisions. The results hitherto obtained cannot be said to have clearly determined these several durations. The interest of the experiments in the present connexion is that they seem pretty clearly to have demonstrated that a preparatory adjustment of the attention tends to shorten the reaction-time, whereas the presence of any distraction which obstructs the process of adjustment lengthens it. Thus, to begin with an unfavourable case, the reaction-time is appreciably lengthened when a disturbing sound (an organ playing in the same room) is at work. In the case of a person whose normal reaction-time was 100 σ (where σ = roth of a second), it rose under these circumstances to 148 r. If the subject is completely taken off his guard, it may even go up to 500 ☛ (} a second). On the other hand, if the process of adjustment is carried out wholly or in part beforehand, the reaction-time is reduced. Thus, if the subject knows by some signal the instant about which the impression is to arrive, the reaction-time may fall from 253 to 76 σ. When the preadjustment is complete, an illusory predating of the impression (i.e., the apparent apprehension of it before the movement of its actual occurrence), may occur, and the subject react too soon.1

§ 6. Duration and Movement of Attention. The process of attention has the immediate effect of fixing an impression. Attention is detention in consciousness.2 The more serious efforts of attention always imply a prolonged fixation of a particular psychical content or group of contents. At the same time, it is evident that the duration of this process of attention

1 These experiments have been elaborated by Prof. Wundt and his pupils. (See Physiol. Psychol. ii. cap. xvi. Cf. Ladd, Elements of Physiol. Psychology, pt. ii. chap. viii.) The results have been experimentally revised and severely criticised by Dr. Münsterberg, Beiträge zur experimentellen Psychologie, heft i. His researches succeed in showing that the several processes do not uniformly occur as successive events in the manner supposed by Wundt, but may under special conditions, viz., when the preliminary or expectant adjustment of attention is directed to the movements to be carried out and not to the sensory signals to be received, be made to overlap. (See James, op. cit., i. p. 432 ff.) At the same time, Münsterberg's arguments do not appear to affect the general truth of the proposition that attention is a process occupying an appreciable time, and varying according as the conditions are favourable or unfavourable.

Ribot emphasises this effect of attention. (Psychologie de l'Attention, p. 6 f.)

has its limits. It has been found that, when we try to attend for a considerable time to one and the same impression, the exertion does not remain of one uniform strength, but periodically rises and falls. This is illustrated in the common experience that in listening to the ticking of a clock, or to the continuous sound of a waterfall, there is an alternate increase and decrease in the intensity of the sound. This fact of periodic rise and fall in the strength of attention has been called the oscillation of attention.

This oscillation is best seen in the case of very feeble impressions lying near the threshold of conscious sensation, as a weak and just perceptible sound. In this case it is ascertained that the impression disappears and reappears in rapid alternations according as attention momentarily fails and recovers itself. These rapid alternations are possibly due to the periodic rise and fall in the accompanying action of the muscles of the tympanum of the ear, or of the other peripheral organs concerned in the production of the sensations. This rapidly recurring and momentary decline in the strength of attention has to be distinguished from the setting in of a conscious fatigue of attention after prolonged mental effort.1

Common experience tells us that we never maintain at one level for a considerable time a close or energetic attention. A fixed stare, such as we may see in a baby, does not involve a prolonged effort of attention. Attention in its more severe forms is always fatiguing, and is thus in its nature intermittent.

Another fact to be noted in this connexion is the tendency to movement or change of direction observable in attention. What may be called the natural condition of attention is a flitting or rapid passing from one object to another. This is illustrated in the incessant turning of eyes and head of a lively monkey in obedience to every new visual or aural impression, and in the infant's similar transition from object to object. Even what we call prolonged concentration of mind on a single topic is in reality a succession of changes in the direction of attention. As already remarked, the unswerving fixation of attention on one object defeats itself, and results in a confusion of consciousness or somnolence of mind, an effect illustrated in

1 On the fact of oscillation, see Wundt, op. cit., ii. p. 253 ff. The reference of these oscillations to a muscular source has been ably urged by Münsterberg, Beiträge zur exper. Psychologie, ii. p. 93 ff.

2 See James, op. cit., i. p. 420 f.

MOVEMENTS OF ATTENTION.

157 the action of monotonous sense-stimuli in inducing the hypnotic state.

These movements are determined, to some extent, by the very mechanism of attention. Thus it is evident that since all attention involves muscular action of some kind, the fatigue that arises from an undue prolongation of this action is favourable to a change in the direction of attention. As every teacher knows, a child, after attending closely to visual objects, as in drawing or other fine work involving the eye, welcomes a change in the direction of attention, as in listening to an oral lesson. A prolonged effort of attention will often tire us for the particular form of mental activity, e.g., looking or listening, without tiring us for other forms.

This fact, again, favours the view that attention is in part, at least, a muscular process. At the same time, it is evident that this fatigue of particular muscles is not the only factor in what we call mental fatigue. Any great and prolonged strain of the attention appears to fatigue the brain as a whole, or at least those nervous centres which are presumably engaged in all forms of attention alike.

Again, the very fact that at any moment we are exposed to the action of a number of rival stimuli favours the movement of attention. When occupied with one particular impression or group of impressions, the intrusion of a new one acts as a diverting force. This is seen more particularly when the new impression is strong or rousing on account of its changefulness, as in the case of all moving objects, which are known by the schoolmaster to be specially distracting. Novel impressions excite by the very fact of their being new, and standing out, so to speak, in relief against the collective horde of our acquired impressions. And when the effect of surprise is added, as in the case of all unexpected objects, the diverting force is increased. Hence, perhaps, the special tendency of children's attention to wander, they being much more under the stimulus of the new, the extraordinary, and the wonderful than older people.1

The readiness with which these transitions of attention can be made varies with a number of circumstances. As already suggested, the existence of any connexion between one impres

1 The full effect of novelty and surprise can only be understood when we come to deal with the feelings.

sion or idea and another greatly favours the movement of attention from the first to the second. As we shall see byand-by, there is a special tendency to a hurrying on from sensations or ideas relatively uninteresting to associated ideas which have a strong interest for us. This is illustrated in our scant and fugitive attention to signs, such as words, under the mastering influence of the ideas signified-a tendency which every proof-reader has to overcome. Again, what is known as liveliness of temperament shows itself mainly, perhaps, in a special mobility of attention or readiness to transfer it to any new object. The bright, impressionable, versatile mind is characterised by rapidity of mental movement. Exercise and practice, moreover, do much to develop this power, just as they serve to strengthen the ability to prolong effort on occasion in some particular direction in patient concentration.

This mobility of attention stands in close connexion with the fundamental attribute of consciousness as changeful, or as made up of a sequence of transitions. In what sense exactly this law of changefulness or "relativity" holds good will have to be discussed later. Here it may suffice to point out that the need of change is conditioned partly by the general psycho-physical fact that all prolonged nervous action tends to lose in energy and to induce fatigue, and partly by the fact that attention can only be maintained at a high level by frequent change of direction.

§ 7. Analytical and Synthetical Action of Attention. All attention is a process of focusing, and as such a concentration or narrowing of the psychical area. In the simplest mode of attention, as when a sound calls forth a reaction, we have the process taking on the aspect of a selective isolation of particular psychical elements. This isolating or analytic aspect of attention becomes particularly marked when we seek to break up the complexes of sensation with a view to single out particular constituents, as in analytically resolving a flavour into its constituents, and fixing attention on certain of these to the disregard of others.

While, however, attention is thus primarily separating or isolating it has, as a second function, the combining of a plurality of sensations or other psychical elements. Thus we may attend not merely to a particular detail of colour in a picture, but to the ensemble of colours, not merely to a con