118. Why is the movement of a billiard ball often accompanied by movements of the players or spectators? 119. What is a voluntary movement? 120. In what manner is will dependent on instinct? 121. Why do deaf children not acquire speech? Can they be taught to speak? 122. Why is the acquisition of foreign speech sounds by grown people often so slow? 123. What is the advantage to the organism of voluntary over instinctive action? 124. Can you describe the three stages of nervous development illustrating the proverb “A burnt child fears the fire”? CHAPTER III COMPLICATIONS OF MENTAL LIFE _A. THE INTELLECT_ § 14. PERCEPTION 1. _Characteristics of Perception_ At every moment of waking life a multitude of impressions are received by the mind through the eyes, the ears, the cutaneous and all other senses, giving information about processes in the external world and in the subject’s own body. However, because of the peculiar laws of mental activity, the actual conscious experience differs greatly from a mere sum of all those impressions--from what would be the content of consciousness if mind were nothing but an accumulation of senses. In order to distinguish the actual consciousness from the abstractly conceived sum of sensations, we use as a specific term the word _perception_. Does not a newspaper look different if held in the right way or turned upside down, a landscape if seen in the ordinary way or through our legs? In the latter case there are in our consciousness a multitude of incomprehensible details, lines, figures, colors; in the former we are conscious of one thing, a landscape, with its divisions, each of these divisions with its subdivisions, and so on. The one consciousness is practically the result only of simultaneous sensory stimulations; the other consciousness, in addition to these stimulations, is determined by the laws of organized mind, by attention, memory, practice.