We must next briefly consider the remaining feature in the psychology of talking birds to which Dr. Wilks has drawn attention, namely, that of inventing sounds of their own contrivance to be used as designative of objects and qualities, or expressive of desires—sounds which may be either imitative of the things designated, or wholly arbitrary. And this, I think, is a most important feature; for it serves still more closely to connect the faculty of vocal sign-making in animals with the faculty of speech in man. Thus, turning first to the case of a child beginning to speak, as Dr. Wilks points out—and nearly all writers on the philosophy of language have noticed—“baby talk” is to a large extent onomatopoetic. And although this is in part due to an inheritance of “nursery language,” the very fact that nursery language has come to contain so large an element of onomatopœia is additional proof, were any required, that this kind of word-invention appeals with ready ease to the infant understanding. But, on the other hand, no one can have attended to the early vocabulary of any child without having observed a fertile tendency to the invention of words wholly arbitrary. As this spontaneous invention of arbitrary words by young children will be found of importance in later stages of my exposition, I will conclude the present chapter by presenting evidence to show the extent to which, under favourable circumstances, it may proceed. Meanwhile, however, I desire to point out that all such cases of the invention of arbitrary vocal signs by young children differ from the analogous cases furnished by parrots only in that the former are usually articulate, while the latter are usually not so. But this difference is easily explained when we remember that hereditary tendency makes as strongly in the direction of inarticulate sounds in the case of the bird, as in the case of the infant it makes in the direction of articulate.