STRUCTURE AND FUNCTIONS OF THE CEREBRUM 157 



of the habitual action. A definite act of inhibition on the part 

 of other associative memories is necessary to prevent the response. 

 All of us have many habits of this sort and they are of the greatest 

 value in our daily lives because on account of them many things 

 that we have to do are more easily done than they would be if 

 the whole mental process upon which the acts depend had to be 

 gone through with at each repetition. 



The tendency to habit formation can be used very effectively 

 in training the child to right actions. It can be used as well in 

 training to right thoughts, since thoughts are associative proc- 

 esses, and these tend to follow the lines laid down by habit. 



Language. Of all the powers of the human mind its power 

 to use language has had as much to do with the progress of the 

 race as any other property it possesses. Language, from the 

 standpoint of cerebral function, is simply a special sort of asso- 

 ciation; the association of arbitrarily selected sounds or written 

 symbols with objects and concepts. Let us, for illustration, con- 

 sider again the case of the child forming the concept mother. Co- 

 incident with the association of her voice, appearance, and other 

 personal attributes into a definite concept is the repeated auditory 

 stimulus of the word mother, heard when she is present or when 

 she is indicated in some way. In course of time this particular 

 succession of syllables is included as part of the concept. Several 

 years later the group of symbols making up the word mother is 

 included in the same concept. Thus language, spoken and writ- 

 ten, becomes indissolubly included in our whole mental equipment. 



It is a curious fact that in man the use of language seems to be 

 not optional, but a necessary factor in his mental development. 

 Two lines of evidence favor this view. The first is the common 

 experience of all of us that we are incapable of thought except 

 in terms of words; coupled with the observation that no race of 

 men exists or is known to have existed without some form of 

 language. The second, and more striking, fact is that certain 

 regions in the association areas of the cerebrum are specially 

 devoted to language associations. Four such regions are known, 

 having been revealed by the physiological effects of their impair- 

 ment through accident or disease. Two of these areas have to 

 do with spoken, and two with written, language. One of the two 

 areas for each form of language is sensory and the other motor. 



