The Principles of Psychology, Vols. 1-2

The reader will remember the reaction-time experiments of which we treated in Chapter III. It happened occasion ally in Wundt's experiments that the reaction-time was reduced to zero or even assumed a negative value, which, being translated into common speech, means that the observer was sometimes so intent upon the signal that his reaction actually coincided in time with it, or even preceded it, instead of coming a fraction of a second after it, as in the nature of things it should. More will be said of these re sults anon. Meanwhile Wundt, in explaining them, says this :

' ' In general we have a very exact feeling of the simultaneity of two stimuli, if they do not differ much in strength. And in a series of ex periments in which a warning precedes, at a fixed interval, the stimu lus, we involuntarily try to react, not only as promptly as possible, but also in such wise that our movement may coincide with the stimu lus itself. We seek to make our own feelings of touch and innervation [muscular contraction] objectively contemporaneous with the signal which we hear ; and experience shows that in many cases we approxi mately succeed. In these cases we have a distinct consciousness of hearing the signal, reacting upon it, and feeling our reaction take place, — aii at one and the same moment." *

" The difficulty of these observations and the comparative infrequency with which the reaction-time can be made thus to disappear shows how hard it is, when our attention is intense, to keep it fixed even on two different ideas at once. Note besides that when this happens, one always tries to bring the ideas into a certain connection, to grasp them as components of a certain complex representation. Thus in the ex periments in question, it has often seemed to me that I produced by my own recording movement the sound which the ball made in dropping on the board." f

The ' difficulty,' in the cases of which Wundt speaks, is that of forcing two non-simultaneous events into apparent combination with the same instant of time. There is no difficulty, as he admits, in so dividing our attention be tween two really simultaneous impressions as to feel them to be such. The cases he describes are really cases of anachronistic perception, of subjective time-displacement, to use his own term. Still more curious cases of it have been most carefully studied by him. They carry us a step farther in our research, so I will quote them, using as far as possible his exact words :

" The conditions become more complicated when we receive a series of impressions separated by distinct intervals, into the midst of which a heterogeneous impression is suddenly brought. Then comes the question, with which member of the series do we perceive the additional impression to coincide? with that member with whose presence it really coexists, or is there some aberration? ... If the additional stimulus belongs to a different sense very considerable aberrations may occur.

" The best way to experiment is with a number of visual impressions (which one can easily get from a moving oDject) for the series, and with a sound as the disparate impression. Let, e.g., an index-hand move over a circular scale with uniform and sufficiently slow velocity, so that the impressions it gives will not fuse, but permit its position at any instant to be distinctly seen. Let the clockwork which turns it have an arrangement which rings a bell once in every revolution, but at a point which can be varied, so that the observer need never know in advance just when the bell-stroke takes place. In such observations three cases are possible. The bell-stroke can be perceived either ex actly at the moment to which the index points when it sounds — in this case there will be no time-displacement ; or we can combine it with a later position of the index— . . . positive time-displacement, as we shall call it ; or finally we can combine it with a position of the index earlier than that at which the sound occurred— and this we will call a negative displacement. The most natural displacement would appa rently be the positive, since for apperception a certain time is always re quired. . . . But experience shows that the opposite is the case : it happens most frequently that the sound appears earlier than its real date — far less often coincident with it, or later. It should be observed that in all these experiments it takes some time to get a distinctly per ceived combination of the sound with a particular position of the in dex, and that a single revolution of the latter is never enough for the purpose. The motion must go on long enough for the sounds them selves to form a regular series — the outcome being a simultaneous per ception of two distinct series of events, of which either may by changes in its rapidity modify the result.

The first thing one remarks is that the sound belongs in a certain region of the scale ; only gradually is it perceived to combine with a particular position of the index. But even a result gained by observation of many revolutions may be deficient in certainty, for accidental combinations of attention have a great influ ence upon it. If we deliberately try to combine the bell-stroke with an arbitrarily chosen position of the index, we succeed without diffi culty, provided this position be not too remote from the true one. If, again, we cover the whole scale, except a single division over which we may see the index pass, we have a strong tendency to combine the bell-stroke with this actually seen position ; and in so doing may easily overlook more than J of a second of time. Eesults, therefore, to be of any value, must be drawn from long-continued and very numerous ob servations, in which such irregular oscillations of the attention neutral ize each other according to the law of great numbers, and allow the

true laws to appear. Although my own experiments extend over many years (with interruptions), they are not even yet numerous enough to ex haust the subject — still, they bring out the principal laws which the attention follows under such conditions." * Wundt accordingly distinguishes the direction from the amount of the apparent displacement in time of the bellstroke. The direction depends on the rapidity of the movement of the index and (consequently) on that of the succession of the bell-strokes. The moment at which the bell struck was estimated by him with the least tendency to error, when the revolutions took place once in a second. Faster than this, positive errors began to prevail ; slower, negative ones almost always were present. On the othei hand, if the rapidity went quickening, errors became nega tive ; if slowing, positive. The amount of error is, in gen eral, the greater the slower the speed and its alterations. Finally, individual differences prevail, as well as differences in the same individual at different times.f

f This was the original 'personal equation ' observation of Bessel. An Observer looked through his equatorial telescope to note the moment at •which a star crossed the meridian, the latter being marked in the telescopic field of view by a visible thread, beside which other equidistant threads appear. "Before the star reached the thread he looked at the clock, and then, with eye at telescope, counted the seconds by the beat of the pendulum. Since the star seldom passed the meridian at the exact moment of a beat, the observer, in order to estimate fractions, had to note its position at the stroke before and at the stroke after the passage, and to divide the time as the meridian-line seemed to divide the space. If, e.g., one had

Wundt's pupil von Tschisch has carried out these ex periments on a still more elaborate scale,* using, not only the single bell-stroke, but 2, 3, 4, or 5 simultaneous impres sions, so that the attention had to note the place of the index at the moment when a whole group of things was happening. The single bell-stroke was always heard too early by von Tschisch — the displacement was invariably 'negative.' As the other simultaneous impressions were added, the displacement first became zero and finally posi tive, i.e. the impressions were connected with a position of the index that was too late. This retardation was greater when the simultaneous impressions were disparate (electric tactile stimuli on different places, simple touch-stimuli, different sounds) than when they were all of the same sort. The increment of retardation became relatively less with each additional impression, so that it is probable that six impressions would have given almost the same result as five, which was the maximum number used by Herr von T.

Wundt explains all these results by his previous obser vation that a reaction sometimes antedates the signal (see above, p< 411). The mind, he supposes, is so intent upon the bell-strokes that its ' apperception ' keeps ripening periodically after each stroke in anticipation of the next. Its most natural rate of ripening may be faster or slower than the rate at which the strokes come. If faster, then it hears the stroke too early ; if slower, it hears it too late. The position of the index on the scale, meanwhile, is noted at the moment, early or late, at which the bell-stroke is subjectively heard. Substituting several impressions for

counted 20 seconds, and at the 21st the star seemed removed by ac from the meridian-thread c, whilst at the 22d it was at the distance be ; then, if ac : be :: 1 : 2, the star would have passed at 21£ seconds. The conditions resemble those in our experiment : the star is the index-hand, the threads are the scale ; and a time-displacement is to be expected, which with high rapidities may be positive, and negative with low. The astronomic ob servations do not permit us to measure its absolute amount ; but that it ex ists is made certain by the fact than after all other possible errors are elimi nated, there still remains between different observers a personal difference which is often much larger than that between mere reaction-times, amount ing . . . sometimes to more than a second." (Op. cit. p. 270.) * Philosophische Studien, n. 601.

the single bell-stroke makes the ripening of the perception slower, and the index is seen too late. So, at least, do I understand the explanations which Herren Wundt and v. Tschisch give.* * Physiol. Psych., 2d ed. n. 273-4; 3d ed. n. 339; Philosophische Studieu, n. 621 fit'. — I know that I am stupid, but 1 confess I find these theoretical statements, especially Wuiidt's, a little ha/y. Herr v. Tschisch considers it impossible thatthe perception of the index's position should come in too late, and says it demands no particular attention (p. 622). It seems, however, that this can hardly be the case. Both observers speak of the difficulty of seeing the index at the right moment. The case is quite different from that of distributing the attention impartially over simulta neous momentary sensations. The bell or other signal gives a momentary sensation, the index a continuous one, of motion. To note any one position of the latter is to interrupt this sensation of motion and to substitute an entirely different percept — one, namely, of position — for it, during a time however brief. This involves a sudden change in the manner of attending to the revolutions of the index; which change ought to take place neither '•ooner nor later than the momentary impression, and fix the index as it is then and there visible. Now this is not a case of simply getting two sen sations at once and so feeling them— which would be an harmonious act; but of stopping one and changing it into another, whilst we simultaneously get a third. Two of these acts are discrepant, and the whole three rather interfere with each other. It becomes hard to ' fix ' the index at the very instant that we catch the momentary impression; so we fall into a way of fixing it either at the last possible moment before, or at the first possible moment after, the impression comes.

This at least seems to me the more probable state of affairs. If we fix the index before the impression really comes, that means that we perceive it too late. But why do we fix it before when the impressions come slow and simple, and after when they come rapid and complex? And why under certain conditions is there no displacement at all? The answer which suggests itself is that when there is just enough leisure between the impressions for the attention to adapt itself comfortably both to them and to the index (one second in W.'s experiments), it carries on the two pro cesses at once; when the leisure is excessive, the attention, following its own laws of ripening, and being ready to note the index before the other impression comes, notes it then, since that is the moment of easiest action, whilst the impression, which comes a moment later, interferes with noting it again ; and finally, that when the leisure is insufficient, the momentary impressions, being the more fixed data, are attended to first, and the index is fixed a little later on. The noting of the index at too early a moment would be the noting of a real fact, with its analogue in many other rhyth mical experiences. In reaction-time experiments, for example, when, in a regularly recurring series, the stimulus is once in a while omitted, the ob server sometimes reacts as if it came. Here, as Wundt somewhere observes, we catch ourselves acting merely because our inward preparation is com plete. The ' fixing' of the index is a sort of action; so that my interpre-

This is all I have to say about the difficulty of having two discrepant concepts together, and about the number of things to which we can simultaneously attend. The things to which we attend are said to interest us, Our interest in them is supposed to be the cause of our at tending. What makes an object interesting we shall see presently ; and later inquire in what sense interest may cause attention. Meanwhile Attention may be divided into kinds in various ways. It is either to

b) Ideal or represented objects (intellectual attention). It is either d) Derived : immediate, when the topic or stimulus is interesting in itself, without relation to anything else ; de rived, when it owes its interest to association with some other immediately interesting thing. What I call derived attention has been named ' apperceptive ' attention. Fur thermore, Attention may be either e) Passive, reflex, non-voluntary, effortless ; or f) Active and voluntary.

Voluntary attention is always derived; we never make an effort to attend to an object except for the sake of some remote interest which the effort will serve. But both sensorial and intellectual attention may be either passive or voluntary. In passive immediate sensorial, attention the stimulus is a sense-impression, either very intense, voluminous, or sud den, — in which case it makes no difference what its nature tation tallies with facts recognized elsewhere ; but Wundt's explanation (if I understand it) of the experiments requires us to believe that an observer like v. Tschisch shall steadily and without exception get an hallucination of a bell-stroke before the latter occurs, and not hear the real bell-stroke after wards. I doubt whether this is possible, and I can think of no analogue to it in the rest of our experience. The whole subject deserves to be gone over again. To Wundt is due the highest credit for his patience in work ing out the facts. His explanation of them in bis earlier work (Vorlesungen lib. Menschen und Thierseele, i. 37-42, 865-371) consisted merely in the appeal to the unity of consciousness, and may be considered quite crude.

may be, whether sight, sound, smell, blow, or inner pain,— or else it is an instinctive stimulus, a perception which, by reason of its nature rather than its mere force, appeals to some one of our normal congenital impulses and has a directly exciting quality. In the chapter on Instinct we shall see how these stimuli differ from one animal to another, and what most of them are in man: strange things, moving things, wild animals, bright things, pretty things, metallic things, words, blows, blood, etc., etc., etc.

Sensitiveness to immediately exciting sensorial stimuli characterizes the attention of childhood and youth. In mature age we have generally selected those stimuli which are connected with one or more so-called permanent inter ests, and our attention has grown irresponsive to the rest.* But childhood is characterized by great active energy, and has few organized interests by which to meet new impres sions and decide whether they are worthy of notice or not, and the consequence is that extreme mobility of the atten tion with which we are all familiar in children, and which makes their first lessons such rough affairs. Any strong sensation whatever produces accommodation of the organs which perceive it, and absolute oblivion, for the time being, of the task in hand. This reflex and passive character of the attention which, as a French writer says, makes the child seem to belong less to himself than to every object which happens to catch his notice, is the first thing which the teacher must overcome. It never is overcome in some people, whose work, to the end of life, gets done in the interstices of their mindwandering.

The passive sensorial attention is derived wrhen the impression, without being either strong or of an instinctively exciting nature, is connected by previous experience and education with things that are so. These things may be called the motives of the attention. The impression draAvs an interest from them, or perhaps it even fuses into a single complex object with them ; the result is that it is brought into the focus of the mind. A faint tap per se is not an interesting sound ; it may well escape being discriminated

* Note that the permanent interests are themselves grounded in certain objects and relations in which our interest is immediate and instinctive. from the general rumor of the world. But when it is a signal, as that of a lover on the window-pane, it will hardly go unperceived. Herbart writes : " How a bit of bad grammar wounds the ear of the purist! How a false note hurts the musician! or an offence against good manners the man of the world ! How rapid is progress in a science when its first principles have been so well impressed upon us that we reproduce them mentally with perfect distinctness and ease! How slow and uncertain, on the other hand, is our learning of the principles themselves, when familiarity with the still more elementary percepts connected with the subject has not given us an adequate predisposition! — Apperceptive attention may be plainly observed in very small children when, hearing the speech of their elders, as yet unintelligible to them, they suddenly catch a single known word here and there, and repeat it to themselves; yes! even in the dog who looks round at us when we speak of him and pronounce his name. Not far removed is the talent which mindwandering school-boys display during the hours of instruction, of notic ing every moment in which the teacher tells a story. I remember classes in which, instruction being uninteresting, and discipline relaxed, a buz zing murmur was always to be heard, which invariably stopped for as Jong a time as an anecdote lasted. How could the boys, since they seemed to hear nothing, notice when the anecdote began ? Doubtless most of them always heard something of the teacher's talk; but most of it had no connection with their previous knowledge and occupations, and therefore the separate words no sooner entered their consciousness than they fell out of it again; but, on the other hand, no sooner did tbe words awaken old thoughts, forming strongly-connected series with which the new impression easily combined, than out of new and old together a total interest resulted which drove the vagrant ideas below the threshold of consciousness, and brought for a while settled attention into their place.1' *

Passive intellectual attention is immediate when we follow ip thought a train of images exciting or interesting per se; derived, when the images are interesting only as means to a remote end, or merely because they are associated with something which makes them dear. Owing to the way in which immense numbers of real things become integrated into single objects of thought for us, there is no clear line to be drawn between immediate and derived attention of an intellectual sort. "When absorbed in intellectual atten tion we may become so inattentive to outer things as to be

'absent-minded,' 'abstracted,' or ' distraits.' All revery or concentrated meditation is apt to throw us into this state. " Archimedes, it is well known, wras so absorbed in geometrical medi tation that he was first aware of the storming of Syracuse by his own death-wound, and his exclamation on the entrance of the Roman sol diers was: Noli turbare drculos nieos! In like manner Joseph Scaliger, the most learned of men, when a Protestant student in Paris, was so engrossed in the study of Homer that he became aware of the massacre of St. Bartholomew, and of his own escape, only on the day subsequent to the catastrophe. The philosopher Carneades was habitually liable to fits of meditation so profound that, to prevent him sinking from inanition, his maid found it necessary to feed him like a child. And it is reported of Newton that, while engaged in his mathematical re searches, he sometimes forgot to dine. Cardan, one of the most illus trious of philosophers and mathematicians, was once, upon a journey, so lost in thought that he forgot both his way and the object of his journey. To the questions of his driver whether he should proceed, he made no answer; and when he came to himself at nightfall, he was sur prised to find the carriage at a standstill, and directly under a gallows. The mathematician Vieta was sometimes so buried in meditation that for hours he bore more resemblance to a dead person than to a living, and was then wholly unconscious of everything going on around him. On the day of his marriage the great Budaeus forgot everything in his philological speculations, and he was only awakened to the affairs of the external world by a tardy embassy from the marriage-party, who found him absorbed in the composition of his Commentarii." *

The absorption may be so deep as not only to banish ordinary sensations, but even the severest pain. Pascal, Wesley, Robert Hall, are said to have had this capacity. Dr. Carpenter says of himself that " he has frequently begun a lecture whilst suffering nem-algic pain so severe as to make him apprehend that he would find it impossible to proceed ; yet no sooner has he by a determined effort fairly launched himself into the stream of thought, than he has found himself con tinuously borne along without the least distraction, until the end has come, and the attention has been released ; when the pain has re curred with a force that has overmastered all resistance, making him wonder how he could have ever ceased to feel it." f

Dr. Carpenter speaks of launching himself by a deter mined effort. This effort characterizes what we called ac- f Mental Physiol., § 124. The oft-cited case of soldiers not perceiving that they are wounded is of an analogous sort. live or voluntary attention. It is a feeling which every one knows, but which most people would call quite indeicribable. We get it in the sensorial sphere whenever we seek to catch an impression of extreme faintness, be it of sight, hearing, taste, smell, or touch ; we get it whenever we seek to discriminate a sensation merged in a mass of others that are similar ; we get it whenever we resist the attractions of more potent stimuli and keep our mind occupied with some object that is naturally unimpressive. We get it in the intellectual sphere under exactly similar conditions : as when we strive to sharpen and make distinct an idea which we but vaguely seem to have ; or painfully discrimi nate a shade of meaning from its similars ; or resolutely hold fast to a thought so discordant with our impulses that, if left unaided, it would quickly yield place to images of an exciting and impassioned kind. All forms of atten tive effort would be exercised at once by one whom we might suppose at a dinner-party resolutely to listen to a neighbor giving him insipid and unwelcome advice in a low voice, whilst all around the guests were loudly laugh ing and talking about exciting and interesting things.

There is no such thing as voluntary attention sustained for more than a few seconds at a time. What is called sustained voluntary attention is a repetition of successive efforts which bring back the topic to the mind.* The topic once brought back, if a congenial one, develops ; and if its de velopment is interesting it engages the attention passively for a time. Dr. Carpenter, a moment back, described the stream of thought, once entered, as ' bearing him along.' This passive interest may be short or long. As soon as it flags, the attention is diverted by some irrelevant thing, and then a voluntary effort may bring it back to the topic again ; and so on, under favorable conditions, for hours to gether. During all this time, however, note that it is not

* Prof. J. M. Cattell made experiments to which we shall refer further on, on the degree to which reaction-times might be shortened by distract ing or voluntarily concentrating the attention. He says of the latter series that "the averages show that the attention can be kept strained, that is, the centres kept in a state of unstable equilibrium, for one second" (Mind, XL an identical object in the psychological sense (p. 275), but a succession of mutually related objects forming an identical topic only, upon which the attention is fixed. No one can possibly attend continuously to an object that does not change.

Now there are always some objects that for the time being ivill not develop. They simply go out ; and to keep the mind upon anything related to them requires such in cessantly renewed effort that the most resolute Will ere long gives out arid lets its thoughts follow the more stimulating solicitations after it has withstood them for what length of time it can. There are topics known to every man from which he shies like a frightened horse, and which to get a glimpse of is to shun. Such are his ebbing assets to the spendthrift in full career. But why single out the spend thrift when to every man actuated by passion the thought of interests which negate the passion can hardly for more than a fleeting instant stay before the mind ? It is like * memento mori ' in the heyday of the pride of life. Nature rises at such suggestions, and excludes them from the view : — How long, O healthy reader, can you now continue thinking of your tomb ? — In milder instances the difficulty is as great, especially when the brain is fagged. One snatches at any and every passing pretext, no matter how trivial or external, to escape from the odiousness of the matter in hand. I know a person, for example, who will poke the fire, set chairs straight, pick dust-specks from the floor, arrange his table, snatch up the newspaper, take down any book which catches his eye, trim his nails, waste the morning anyhow, in short, and all without premedita tion, — simply because the only thing he ought to attend to is the preparation of a noonday lesson in formal logic which he detests. Anything but that !

Once more, the object must change. When it is one of sight, it will actually become invisible ; when of hearing, inaudible, — if we attend to it too unmoviugly. Helmholtz, who has put his sensorial attention to the severest tests, by using his eyes on objects which in common life are ex pressly overlooked, makes some interesting remarks on this point in his chapter on retinal rivalry.* The phe- * Physiologische Optik, § 32. nomenon called by that name is this, that if we look with each eye upon a different picture (as in the annexed stereo scopic slide), sometimes one picture, sometimes the other,

or parts of both, will come to consciousness, but hardly ever both combined. Helmholtz now says : " I find that I am able to attend voluntarily, now to one and now to the other system of lines ; and that then this system remains visi ble alone for a certain time, whilst the other completely vanishes. This happens, for example, whenever I try to count the lines first of one and then of the other system. . . . But it is extremely hard to chain the attention down to one of the systems for long, unless we associate with our looking some distinct purpose which keeps the ac tivity of the attention perpetually renewed. Such a one is counting the lines, comparing their intervals, or the like. An equilibrium of the attention, persistent for any length of time, is under no circumstances attainable. The natural tendency of attention when left to itself is to wander to ever new things ; and so soon as the interest of its object is over, so soon as nothing new is to be noticed there, it passes, in spite of our will, to something else. If we wish to keep it upon one and the same object, we must seek constantly to find out something new about the latter, especially if other powerful impressions are attracting us away.''