136 MENTAL EVOLUTION IN MAN. 



or expressive of desires — sounds which maybe 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 onomatopoeia 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. 



There still remains one feature in the psychology of talk- 

 ing birds to which I must now draw prominent attention. So 

 far as I can ascertain it has not been mentioned by any 

 previous writer, although I should think it is one that can 

 scarcely have escaped the notice of any attentive observer of 

 these animals. I allude to the aptitude which intelligent 

 parrots display of extending their articulate signs from one 

 object, quality, or action, to another which happens to be 



