"As we survey the various stages of evolution, from the simplest one-cell creatures up to man. we see a steady improvement in the methods of learning and adaptation to a hostile world. Each step in learning ability gives better adaptation and greater chance of survival. We are carried a long way up the scale by innate reflexes and rudimentary muscular learning faculties. Habits indeed, not rational thought, assist us to surmount most of life's obstacles. Most, but by no means all; for learning in the high mammals exhibits the unexplained phenomenon of "insight," which shows itself by sudden changes in behavior in learning situations -- in sudden departures from one method of organizing a task, or solving a problem, to another. Insight, expectancy, set, are the essentially "mind-like" attributes of communication, and it is these, together with the representation of concepts, which require physiological explanation. At the higher end of the scale of evolution, this quality we call "mind" appears more and more prominently, but it is at our own level that learning of a radically new type has developed -- through our powers of organizing thoughts, comparing and setting them into relationship, especially with the use of language. We have a remarkable faculty of forming generalizations, of recognizing universals, of associating and developing them. It is our multitude of general concepts, and our powers of organizing them with the aid of language in varied ways, which forms the backbone of human communication, and which distinguishes us from the animals. (p. 304)"