There is less agreement as to the psychical method of the early development. Probably it was a complex of all the various psychical forces usually urged. First among these may be con sidered emotional expressiveness, as indicated above. The most primitive type of word was then the interjection (q.v.), which might be varied in three ways: by syllabic variation, by syllabic repetition. or by an alteration in pitch of utterance. From the third of these. alteration in pitch. springs the theory that a kind of sing ing, or singing-language, preceded later speech. The fact that gregarious associations were doubt less at first but temporary congregations for dance or war, where utterance assumes the form of a rhythmic chant, has given rise to a variation of the song theory. the germ of language being found in this rhythmic chant. The second psy chic force in the formation of language. which is often regarded as the chief one, is imitation. This is supposed to have acted in two ways—in ono matopoetic imitation of the typical sounds of nature, as when the cry of an animal becomes that animal's name: and in direct imitation. the direct learning of words as the child learns them from noting the habitual utterances of others.
Doubtless all of these factors were present in the formation of language; but it should he noted that the really significant differentia of human speech is not to be found in the nature of its motive or form of expression, hut in the relation of this expression to thought. The stupendous step was the creation of conventionalized or sym bolic expressions. An onomatopoetic utterance, as the bird's call meaning the bird uttering it. is directly incorporated in immediate experience: it is instinctive, as we observe with children. But when such utterance becomes universalized, mean ing all birds or birds in general. whether gifted with like call or not, then we have the abstrac tion which lies at the base of all reasoning and makes intellectual evolution possible. Only the possession of a brain much superior to that of any other animal can have enabled man to de velop a language adapted to reason from the primitive and instinctive signal language.
The problems arising from the relation of lan guage to thought. with which the psychologist has to deal. are of three types: (I) The onto genetic study of the acquisition of language by children: (2) the relations of words to thoughts and to the brain: (3) questions of metaphysics and social psychology. due to the function of lan guage as a means of communication of mind with mind.
The first of these three is an important branch of child-study. and is ordinarily undertaken for the sake of pedagogical inferences, to be drawn from observations of the child's natural acquisi tion of language. For example, studies of the vocabularies of children have been used to test the degree and kind of discriminations they are capable of making, and so to serve a- guides for the course of their education; and again, systems for the study of foreign languages have been devised from observation of the natural, or child, method. But investigations of children's language
have also been extensively employed as bases for inference as to the phylogenesis of human language in general. Very many inferences as to the origin of speech have thus been founded upon observation of imitative and inventive ex pression in children, and of their songs and games. While such inferences are often suggest ive, it is not always noted that they are subject to the serious objection that children are taught. and acquire their language from a set model, whereas primitive speech, as a creation de no-ro, could have had no such aid.
The problems raised by the relations of lan guage to thought and to the brain are many and complicated. hut may be roughly divided into three classes. There are, first, the psycho-physi ologieal questions as to the nature and functions of speech; second, the neurological questions con nected with the cerebral localization of speech and with its various diseases, such as amnesia. aphasia. and agraphia; and third, the analytical questions of association, verbal representation, and the dependence of ideation upon this and upon vocabulary. The third class of questions alone are purely psychological, and they lie at the basis of our most exacting speculations. Ques tions of association usually appear as problems connected either with the spontaneous sequence of words in the mind or with their power to suggest other images. Questions of verbal repre sentation are concerned mainly with the nature and degree of word images in the mind. Ques tions of the dependence of ideation upon verbal representation and vocabulary are much more extensive. ranging from relatively simple prob lems of an assoeiational type to complex ques tions of logic. theory of judgment. and the like. Of interest in this connection is the speculation sometimes advanced that if man were isolated he would lose the faculty of language. This is in ferred from the premise that language is solely a means of communication of mind with mind. It is fair to affirm that psychology of recent years has established the fact that a large amount of our reasoning is mediated by language alone. and is made possible only through the abstractions which word. enable. Since this is the case: man could not wholly lose the faculty of language so long as his mind remained rationally active. Need for the so-ealled 'internal speech.' the mental use of words, would persist. forming as it does one of the great utilities of language.