In the preceding chapter we asked: What is it that determines the horse's movements? Independent thinking, or external signs?--We found that it was solely external signs, which we described as certain postures and movements of the questioner. Beyond a doubt these necessary signs were given involuntarily by all the persons involved and without any knowledge on their part that they were giving any such signs. This is to be seen from their statements, which cannot be cavilled at, as well as from the fact that several of them even to-day still doubt the correctness of the explanation which we are here offering. I myself for some time made these involuntary movements quite unwittingly and even after I had discovered the nature of these movements and had thus become enabled to call forth at will all the various responses on the part of the horse, I still succeeded in giving the signs in the earlier naive involuntary manner. It is not easy, to be sure, to eliminate at once the influence of knowledge and to focus attention with the greatest amount of concentration on the number desired, rather than upon the movement which leads to a successful reaction on the part of the horse. To some this may appear impossible, but those who are accustomed to do work in psychological experimentation, will not deny the possibility of such exclusive concentration upon certain ideas. If we now ask: "What occurred in the mind of the questioners, while they were giving the signs?", the answer can be found only by way of the process which in psychology is technically called "introspection", i. e. observation of self. In the following we will give the most important results of this process of self-observation, which took place in the same period in which the observations recorded in the preceding chapter were made.