124 MENTAL EVOLUTION IN MAN. 



We may be sure, however, that words arc never understood 

 unless tones arc Hkewise so, and that understanding of words 

 may be assisted by understanding of the tones in which they 

 are uttered. Therefore, the only method of ascertaining 

 where words as such are first understood, is to find where they 

 are first understood irrespective of the tones in which they are 

 uttered. This criterion — so far, at least, as my evidence goes 

 — excludes all cases of animals obeying commands, answering 

 to their names, &c., with the exception of the higher 

 mammalia. That is to say, while the understanding of 

 certain tones of the human voice extends at least through 

 the entire vertebrated series, * and occurs in infants only a 

 few weeks old ; the understanding of words without the assist- 

 ance of tones appears to occur only in a few of the higher 

 mammalia, and first dawns in the growing child during the 

 second year.t 



The fact that the more intelligent Mammalia are able to 

 understand words irrespective of tones is, as I have said, 

 important ; and therefore I shall devote a few sentences to 

 prove it. 



My friend Professor Gerald Yeo had a terrier, which was 

 taught to keep a morsel of food on its snout till it received 

 the verbal signal " Paid for ; " and it was of no consequence 

 in what tones these words were uttered. For even if they 

 were introduced in an ordinary stream of conversation, the 

 dog distinguished them, and immediately tossed the food into 

 his mouth. Seeing this, I thought it worth while to try 

 whether the animal would be able to distinguish the words 

 "Paid for" from others presenting a close similarity of sound; 



* See Anhiial Intelligence : for Fish, p. 250 ; for Frogs and Toads, p. 225 ; for 

 Snakes, p. 261 ; for Birds and Mammals in various parts of the chapters devoted to 

 these animals. The case quoted on the authority of Bingley regarding the tame 

 bees of Mr. Wildman, which he had taught to obey words of command (p. 189), 

 would, if corroborated, carry the faculty in question into the invertebrated series. 



t Although the ages at which talking proper begins varies much in different 

 children, it may be taken as a universal rule — as stated in the last foot-note — 

 that words, and even sentences, are understood long before they are intelligently 

 articulated ; although, as previously remarked, even before any words are under- 

 stood meaningless syllables may be spontaneously or instinctively articulated. 



