Table 1 shows relations between age, brain weight, and speech performance, up to 23 months, 1070 grams, and the use of full sentences. By 17 years, the brain reaches and levels off at 1450 grams and the number of words, levels of abstraction, etc., are so large as to be difficult to assess.
In these processes, what are the minimum necessary but not necessarily sufficient factors?[20] On the biological side, modern theory concentrates on two factors: total numbers of neurons and the number of interconnections between them. On the psychological side, modern theory concentrates on the numbers of occurrences of reinforced contingencies experienced, the number of repetitions, and the number of adequate presentations from the accepted set of the consensus known as “native language,” and the total numbers of sets in the stored memories at a given age. In addition, of course, is the adequate development of the transmitting and of the receiving equipment needed for speech and its ancillary behaviors.
On the biological side, modern neurology says the number of neurons in the human brain reaches maximum value before birth at about 13 billions. After this point, the increase in weight consists of increased numbers of fibers, increased connections, increased size of elements, and increased efficiency and selectivity of transmission. Thus the increase in weight of the human brain from about 400 to 1400 grams seems to be devoted to improving its internal (as well as external) communication, storage, and computation networks. As I have stated elsewhere (Man and Dolphin), it is my impression that there exist critical threshold values in the brain’s growth pattern at which certain kinds of performance become possible. Complex speech acquisition seems related to brain weights of 800 to 1000 grams, but no smaller. This assumes, of course, numbers of neurons (10¹⁰) and numbers of connections and opportunities for learning and time to learn commonly found with humans.
The critical psychological factors in speech acquisition are slowly being dug out and described.[21][22] Among these the most important seem to be a continuous background of presentations to the child in rewarding circumstances of speech and its close relations to objects, actions, satisfaction of needs, and persons. Imitation of one’s use of facial and vocal apparatus appears spontaneously in the happy child. The virtuosity of the child as a mimic is truly astonishing.
I am also impressed by evidence for what I call the “transactional drive.” A bright child seems to seek and respond best to those persons who respond in kind, back and forth in exchanges of sounds and linked actions. For example, if one starts such a transaction with a child of 22 months with a loud word, if he is ready, he may return his version of the word or a slight variant; if one replies with another variant the child replies with still a third, or even suddenly with a new word, and so on back and forth in a transactional vocal dance. Or one may reply to a child who invites such an exchange to begin. Such exchanges seem to function as rewards of themselves, and hence the name, “transactional drive.” This phenomenon is more than mere mechanical slavish mimicry. It seems to aid in perfecting pronunciation, increases vocabulary, increases the bonds with other persons, serves to substitute the “consensus-dictionary” words for the private baby words, and is thus essential to learning a language of one’s own species. It is thus that the child “becomes human.”
As the child ages and grows, the exchanges lengthen, and the time during which each member of the dyad is quiet while the other speaks becomes longer, until finally for a half hour or so, I am lecturing and you are at least quiet, if not listening.
How does all of this relate to modern dolphins, porpoises, and whales? From the vast array of scientific facts and theories about our own species, a few of those which I feel are useful in approaching another species to evaluate its intelligence are discussed above. But before I make connections there, let us attenuate some interfering attitudes and points of view, some myths not so modern; these interfering presumptions can be stated as follows:
(1) No animal has a language comparable to a human language. (2) No animal is as intelligent as man. (3) Man can adapt himself to any environment quite as well as any animal. (4) Intelligence and intellect can be expressed only in the ways man expresses or has expressed them. (5) All animal behavior is instinct-determined. (6) None of man’s thought and behavior is so determined. (7) Only man thinks and plans; animals are incapable of having a mental life. (8) Philosophy and contemplative and analytic thought are characteristic only of man, not of any animal.
All of these statements stem from ignorance and anthropocentricity. For example, who are we to say that whales, dolphins, and porpoises are to be included as “dumb beasts”? It would be far more objective and humble to tell the truth—we don’t know about these animals because we haven’t “been there yet.” We have not lived in the sea, naked and alone, or even in mobile groups, without steel containers to keep out the sea itself. For purposes of discussion let us make the following assumptions which push counter to the current of bias running deep among us: