Other Glimpses of Intelligence A squirrel is just as clever as it needs to be and no more; and of some vanishing mammals, like the beaver, not even this can be said. Humdrum non-plastic efficiency is apt to mean stagnation. Now we have just seen that in the play of young mammals there is an indication of unexhausted possibilities, and we get the same impression when we think of three other facts. (_a_) In those mammals, like dog and horse, which have entered into active cooperative relations with man, we see that the mind of the mammal is capable of much more than the average would lead us to think. When man's sheltering is too complete and the domesticated creature is passive in his grip, the intelligence deteriorates. (_b_) When we study mammals, like the otter, which live a versatile life in a very complex and difficult environment, we get an inspiriting picture of the play of wits. (_c_) Thirdly, when we pass to monkeys, where the fore-limb has become a free hand, where the brain shows a relatively great improvement, where "words" are much used, we cannot fail to recognise the emergence of something new--a restless inquisitiveness, a desire to investigate the world, an unsatisfied tendency to experiment. We are approaching the Dawn of Reason. THE MIND OF MONKEYS Sec. 8 There is a long gamut between the bushy-tailed, almost squirrel-like marmosets and the big-brained chimpanzee. There is great variety of attainment at different levels in the Simian tribe. Keen Senses To begin at the beginning, it is certain that monkeys have a first-class sensory equipment, especially as regards sight, hearing, and touch. The axes of the two eyes are directed forwards as in man, and a large section of the field of vision is common to both eyes. In other words, monkeys have a more complete stereoscopic vision than the rest of the mammals enjoy. They look more and smell less. They can distinguish different colours, apart from different degrees of brightness in the coloured objects. They are quick to discriminate differences in the shapes of things, e.g. boxes similar in size but different in shape, for if the prize is always put in a box of the same shape they soon learn (by association) to select the profitable one. They learn to discriminate cards with short words or with signs printed on them, coming down when the "Yes" card is shown, remaining on their perch when the card says "No." Bred to a forest life where alertness is a life-or-death quality, they are quick to respond to a sudden movement or to pick out some new feature in their surroundings. And what is true of vision holds also for hearing. Power of Manipulation