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.' If atthe fourth momentof time weannihilate thethinker andexamine how thelast pulsation ofhis consciousnesswas made, we find that it was an awareness of the whole content with same most prominent, andthe other parts of the thing known relatively less distinct.With each prolongation of the schemein the time-direction, the summit of the curve of section would come further towards the end ofthe sentence.If we make a solid wooden frame with the sentence written on its front, and thetime-scale on one of its sides, if we spread flatly a sheet of India rubber over its top, on whichrectangular co-ordinates are painted, and slide a smooth ball under the rubber in the directionfrom 0 to 'yesterday,' the bulging of the membrane along this diagonal at successive momentswill symbolize the changing of the thought's content in a way plain enough, after what has beensaid, to call for no more explanation.Or to express it in cerebral terms, it will show the relativeintensities, at successive moments, of the several nerve-processes to which the various parts ofthe thought-object correspond.The last peculiarity of consciousness to which attention is to be drawn in this first roughdescription of its streamis that[p.284] 5) It is always interested more in one part of its object than in another, and welcomesand rejects, or chooses, all the while it thinks.The phenomena of selective attention and of deliberative will are of course patent examples ofthis choosing activity.But few of us are aware how incessantly it is at work in operations notordinarily called by these names.Accentuation and Emphasis are present in every perception wehave.We find it quite impossible to disperse our attention impartially over a number ofimpressions.A monotonous succession of sonorous strokes is broken up into rhythms, now ofone sort, now of another, by the different accent which we place on different strokes.Thesimplest of these rhythms is the double one, tick-tóck, tick-tock, tick-tóck.Dots dispersed on asurface are perceived in rows and groups.Lines separate into diverse figures.The ubiquity of thedistinctions, this and that, here and there, now and then, in our minds is the result of our layingthe same selective emphasis on parts of place and time.Get any book for free on: www.Abika.com THE PRINCIPLES OF PSYCHOLOGY172But we do far more than emphasize things, and unite some, and keep others apart.We actuallyignore most of thethings before us.Let me briefly show how this goes on.To begin at the bottom, what are our very senses themselves but organs of selection? Out of theinfinite chaos of movements, of which physics teaches us that the outer world consists, eachsense-organ picks out those which fallwithin certain limits of velocity.To these it responds, but ignores the rest as completely as if theydid not exist.It thus accentuates particular movements in a manner for which objectively thereseems no valid ground; for, as Lange says, there is no reason whatever to think that the gap inNature between the highest sound-waves and the lowest heat-waves is an abrupt break like thatof our sensations; or that the difference between violet and ultra-violet rays has anything like theobjective importance subjectively represented by that between light and darkness.Out of what isin itself an undistinguishable, swarming continuum, devoid of distinction or emphasis, our sensesmake for us, by attending to this motion and ignoring that, [p.285] a world full of contrasts, ofsharp accents, of abrupt changes, of picturesque light and shade.If the sensations we receive from a given organ have their causes thus picked out for us by theconformation of the organ's termination, Attention, on the other hand, out of all the sensationsyielded, picks out certain ones as worthy of its notice and suppresses all the rest.Helmholtz'swork on Optics is little more than a study of those visual sensations of which common men neverbecome aware - blind spots, muscS volitantes, after images, irradiation, chromatic fringes,marginal changes of color, double images, astigmatism, movements of accommodation andconvergence, retinal rivalry, and more besides.We do not even know without special training onwhich of our eyes an image falls.So habitually ignorant are most men of this that one may beblind for years of a single eye and never know the fact.Helmholtz says that we notice only those sensations which are signs to us of things
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