could the listener follow the part assigned to some special group of instruments in the orchestra, while he still hears the full harmony? and how, still more, could the conductor single out the particular violin-player, who has mistaken a note, from the group of sixteen who are all playing precisely the same part? We may suppose, therefore, that _one and the same pattern of attention is due to very varied combinations of reinforcing and inhibiting nerve-forces_. How then shall we account for the fact that, in any given instance, vividness and obscurity are inversely proportional (p. 100)? The reason seems to be—though we could not have learned it from the experiments on the frog—that a reinforcement and a corresponding inhibition always go hand in hand; you cannot reinforce one process without at the same time inhibiting others, and you cannot inhibit without reinforcing. _The nerve-forces are thus interlinked or, as we might say, double-acting._ We are struck by the inhibition in Carpenter’s case; but the case has another side; for the more successful the inhibition of the neuralgia, the better was the lecture delivered. So we are struck by the reinforcement in the case of the conductor; but that, too, has another side; for the keener his attention to the music, the more oblivious is he of his other surroundings. We shall come back later to this notion of the interlinking of the nerve-forces, and shall indicate the evidence upon which it rests. In summary, we may repeat our general statement that _vividness is paralleled by nervous reinforcement, and obscurity by nervous inhibition_. Only we must realise that the processes actually going on in the brain may be very complicated; many separate forces may be at work behind the single mental pattern, and their action may be brought about in different ways; and we must remember also that every one of these separate forces is double-faced, reinforcing and inhibiting at the same time. Questions and Exercises (1) “So numerous and varied are the ramifications of attention, that we find it defined by competent authorities as a state of muscular contraction and adaptation, as a pure mental activity, as an emotion or feeling, and as a change in the clearness of ideas. Each of the definitions can be justified from the facts, if we put the chief emphasis now upon one phase and now upon another of its varied expressions” (W. B. Pillsbury, Attention, 1908, 1). Discuss this passage. (2) Give instances, from your own experience, of the three levels of attention. Trace the development (still from your own experience) of derived primary from secondary attention. (3) Describe carefully the attitudes (_a_) of the scout (secondary visual attention) and (_b_) of the eavesdropper (secondary auditory attention). How do you account for their difference?