74 K. S. LASHLEY AND S. I. FRANZ 



rately the character of a certain loss. Such a defect might 

 apparently be motor. If this should be so we have reason to 

 believe that a required movement could not be initiated from 

 the cerebrum by any form of stimulus, whether light or sound 

 or touch. If, however, the defect be sensory, let us say visual, 

 the problem changes. A stimulus of that particular kind would 

 not serve to produce a habit of any character, whereas other 

 sensory stimuli (sound, touch, smell, etc.) could be used as the 

 means to produce habits. By changing the conditions both on 

 the sensory and motor sides it is also possible to discover what 

 may be termed an " association" loss, although this is in some 

 particulars more difficult than the sensory and motor losses. 



After a cerebral accident in man there is also the possibility 

 of determining the degree of retention, the characters of the 

 retained habits, and the capability of formation of new habitual 

 modes of reaction, i.e., behavior. In the clinical examinations 

 of man chief, and frequently exclusive, use is made of the speech 

 habits, although the exclusive employment of speech as the 

 mode of reaction has certain disadvantages. They are not 

 always obvious and they appear to be little appreciated. One 

 of these is that an inability may be reported by speech which 

 by other means it is possible to discover does not exist. This 

 fact is recognized in certain well developed cases which in the 

 past have been called hysterical. It is now admitted that in 

 many other individuals similar " hysterical" symptoms may 

 exist without there being easily recognized signs. Diverse 

 mental states, such as dementia, great joy, or even a lack of 

 understanding, may result in variations in speech habits which 

 mask other effects. This being so, it is clear that to accept as 

 final evidence of a defect a negation (by speech) is similar to 

 the conclusion that an animal sees if the eyes are turned towards 

 the stimulating light. The experimental method should be 

 extended and the habit reaction method especially should be 

 applied to the determination of defects in man after cerebral 

 lesions. The limitation of clinical studies on cerebral functions 

 to the consideration of speech reactions as the motor side of 

 learned reactions can in many cases result only in superficial 



