=The Ideational Excitement of the Centre.=--But if the peripheral part of the picture in this experiment be not physically accommodated for, what is meant by its sharing our attention? What happens when we 'distribute' or 'disperse' the latter upon a thing for which we remain unwilling to 'adjust'? This leads us to that second feature in the process, the '_ideational excitement_' of which we spoke. _The effort to attend to the marginal region of the picture consists in nothing more nor less than the effort to form as clear an_ IDEA _as is possible of what is there portrayed._ The idea is to come to the help of the sensation and make it more distinct. It may come with effort, and such a mode of coming is the remaining part of what we know as our attention's 'strain' under the circumstances. Let us show how universally present in our acts of attention is this anticipatory thinking of the thing to which we attend. Mr. Lewes's name of _preperception_ seems the best possible designation for this imagining of an experience before it occurs. It must as a matter of course be present when the attention is of the intellectual variety, for the thing attended to then _is_ nothing but an idea, an inward reproduction or conception. If then we prove ideal construction of the object to be present in _sensorial_ attention, it will be present everywhere. When, however, sensorial attention is at its height, it is impossible to tell how much of the percept comes from without and how much from within; but if we find that the _preparation_ we make for it always partly consists of the creation of an imaginary duplicate of the object in the mind, that will be enough to establish the point in dispute. In reaction-time experiments, keeping our mind intent upon the motion about to be made shortens the time. This shortening we ascribed in Chap. VIII to the fact that the signal when it comes finds the motor-centre already charged almost to the explosion-point in advance. Expectant attention to a reaction thus goes with sub-excitement of the centre concerned. Where the impression to be caught is very weak, the way not to miss it is to sharpen our attention for it by preliminary contact with it in a stronger form. Helmholtz says: "If we wish to begin to observe overtones, it is advisable, just before the sound which is to be analyzed, to sound very softly the note of which we are in search.... If you place the resonator which corresponds to a certain overtone, for example _g´_ of the sound _c_, against your ear, and then make the note _c_ sound, you will hear _g´_ much strengthened by the resonator.... This strengthening by the resonator can be used to make the naked ear attentive to the sound which it is to catch. For when the resonator is gradually removed, the _g´_ grows weaker; but the attention, once directed to it, holds it now more easily fast, and the observer hears the tone _g´_ now in the natural unaltered sound of the note with his unaided ear."