We should think of the fact that, for walking, a correlation of hundreds or thousands of musculars fibers is needed. Dynamically, i.e. depending on the specifics of any individual movement, on the previous behaviour, on the anticipated behaviour, on the goal to be attained and on the various external perturbations, all these fibres will be activated/deactivated in a precise order, each with the suitable intensity to solve the given problem. At any moment the problems which could appear are anticipated and the corrections are made, before the problems occur. The number of models (which are built or activated), associated with this type of activity, can be tens or hundreds in a second. Example: The working speed of a model Related to anticipation by simulation on a model, I have seen a photo of a baseball player that was trying to catch a fast ball in flight. The high-speed photo showed the ball flying directly into the glove of the player. The sensational in this picture is that the eyes were looking at the place where the ball had been some time before. The model for catching the ball has anticipated the position of the ball based on the previous information coming from the eyes. The action was a success, even if the eyes were unable to give the real time information, and in spite of the fact that the hand can not move very fast. This example illustrates the huge advantage of the construction and operation of models. The effective speed of action can be considerably higher than the intrinsic speed of action of the components. Hikers who go on difficult treks with heavy backpaks, which change slightly their position, know that hiking can be done with exceptional stability. Personally, the immense capacities of the brain to process information, and the speed of execution of these incredibly complicated operations, have always amazed me. Associated with the above issue, I had a situation on a trek, carrying a heavy backpack, when a stone slipped from under my foot and I fell. The active models were not able to anticipate this possibility. In this case, the capacity to build a new model suitable to the external reality is reduced. As we know, PSM is activated instead. However, I am still amazed that I was not hurt during that fall (it was practically a controlled fall, but outside my consciousness). Usually, PSM tries to save what can be still saved, and it is even possible, that it will accept sacrificing an arm, to save what is more important.