The Great Apes The•Great Apes. A Study of Anthropoid Life.

By Robert M.

Accoanrxa to Hoppius, an eighteenth-century zoologist, one would benefit philosophy greatly by spending a day with apes, " exploring how far human wit exceeds theirs, what distance lies between Brutish and rational discrimination." Professor and Mrs. Yerkes have spent many days in this occupation, and as a result have produced an exceptionally valuable treatise. This is not Professor Yerkes' first con- tribution to the subject of anthropoid behaviour. Apart from a semi-popular work entitled Almost Human and papers on the behaviour of lower animals, he is well known to students for several monographs on the psychology of the chimpanzee and gorilla. In The Great Apes he and Mrs. Yerkes have drawn together almost everything that has been written on anthropoid behaviour. It presents little that is new, but this does not prevent it from being the most useful work on the living anthropoid that has yet been written. The book is " offered as an informational and biblio- graphic source for investigators, students, and lay readers whose curiosity may lead them into the paths of anthro- poid life."

Human interest in the behaviour of apes and monkeys long preceded the scientific recognition of man's evolutionary connexion with the lower primates, and no advanced psycho- logical technique was necessary to determine that the behaviour and adaptability of the monkey shows closer resemblance to the human than does that of the dog. In many parts of the world, for instance, native folklore abounds with legends demonstrating the sagacity of monkeys and apes. Scientific interest, however, was not stirred until the middle of the last century. The upheaval caused by Darwin proved a strong stimulus to close observation of infra-human primate behaviour, and resulted in the collection of numerous observations, many, however, of doubtful scientific value, revealing no more than was already apparent, i.e., that the behaviour of primates is different from that of other mammals, and that psychologically monkeys and apes are closer to man than are lower mammals. Sociologists also commenced to take an interest in the natural habits of the anthropoid ape, and, depending upon their particular bias, to find in the accounts of naturalists support for theories of instinctive human monogamy or human promiscuity. The first critical studies of primate behaviour were those of Thorndike and Hobhouse, both published in 1901. Hob- house's contribution was of particular importance, and though its influence may be traced through much of the work that has appeared since its publication, it is as a rule either overlooked or scantily acknowledged. General interest in ape psychology was not roused in this country until the publication of an English translation of Kohler's work on the chimpanzee in. 1925.

The Great Apes contains the results of observation and research on the gibbon, orang-outan, chimpanzee, and gorilla.

• It opens with an historical account of our knowledge of the

• four anthropoids. Then follow sections devoted to detailed discussion of each in turn, the book closing with a com- parison of the four types, first with one another and then with the lemur and monkey. Structural appearance, habitat, feeding habits, social relations, sexual life history, temperament, affective behaviour, vocalization, perception,

adaptation, memory, abstraction and generalization, these and many other features are discussed by Professor and Mrs. Yerkes. Here we can refer br;efly only to their con- clusions regarding intelligence.

Intelligence is judged by the normal behaviour of an animal and by its reactions under experimental conditions.

A simple example of an experimental method is the following.

A banana is placed out of a chimpanzee's reach. A stick sufficiently long to reach the fruit is placed near by. The object of the experiment is to see whether the animal will use the stick as an instrument to draw in the fruit. According to Professor and Mrs. Yerkes, " the chimpanzee commonly exhibits trial and error as adaptational method. . . . But there are times when blind trial gradually gives place to insight and in the end the solution seems to involve thorough perceptual grasp of the essential features of the problematic situation and a measure of insight which, had it originally appeared, would have obviated mistakes." In this the chimpanzee contrasts strikingly with the lower mammal, who is tied to the method of trial and error. The authors also infer in the chimpanzee a relatively high degree of

memory, indications of constructive imagination, and rudi- mentary powers of abstraction and generalization. " Indeed, were it capable of speech and amenable to domestication, this remarkable primate might quickly come into competition with low-grade manual labor in human industry."

Judged by the same standards, ideational behaviour is also exhibited by the other apes, but in different degrees.

In affective traits the authors consider the chimpanzee to be nearest to man, then, in order, the gorilla, orang-outan, and gibbon ; in cognitive traits they place the gorilla before the chimpanzee. As the only monkey that has been investi- gated experimentally' shows far less insight than does any of the apes, the psychological series leading up to man becomes the same as the series postulated by morphologists.

Professor and Mrs. Yerkes have illustrated their treatise with a magnificent collection of photographs. They have also included a comprehensive bibliography. The book has one important disadvantage. It is unnecessarily long. Without in any way departing from their purpose and without omitting any facts, they could have achieved their aim in many fewer words. Repetition is common. Although the first part is devoted to an historical account of the literature

of all the apes, each succeeding section opens with a recountal of the history of the type that is being considered. Many useless reports of behaviour are quoted at length ; nor arc

second-hand accounts neglected. The work is marred also

by some rather exuberant passages. In one place the authors refer to the excellence of a little book entitled My Friend Toto, and remark that they would " like to quote My Friend Toto in toto." In another they quote a paragraph from a book by Garner, and then add : " We beg to make corrections in this paragraph as follows : Horniday should be spelled Hornaday, and the initials of Wallace are A. R. instead of the reverse. The only single point in which we can agree with Garner is that he never studied the orang-outan." Under the circumstances, it seems rather a pity that time was spent quoting him.