49° POPULAR SCIENCE MONTHLY. 



And if I use an unfamiliar typewriter, I must assume a more attentive 

 attitude to my manipulations, working out some of them deliberately 

 anew; and I am quite likely to find myself intermittently attempting 

 to perform on the new machine a manipulation that is proper only to 

 the more familiar one. The relations are distinctly intensified when 

 the coordination involved is more deep-seated, less consciously realized, 

 more distinctively a function of the automatic centers. Activities 

 guided primarily by the feelings accompanying muscular contractions, 

 in contrast to those guided primarily by vision, furnish the most favor- 

 able instances of what is here involved. A very striking one is found 

 in the attempt to ride a tricycle by one accustomed to the bicycle. The 

 equilibration of the bicycle requires that one lean with the machine, to 

 the right in turning to the right, to the left in turning to the left. 

 This in itself is contrary to the normal walking habit of saving our- 

 selves from falling by shifting to the opposite side, and had itself to be 

 learned with some difficulty, because opposed to another ingrained tend- 

 ency. Seated on a tricycle, the bicyclist unwittingly and in spite of 

 himself maintains the bicycle-balancing habit, and is surprised to find 

 the simple tricycle, which one without any experience with either can 

 guide easily, quite beyond his control. The old habit persists and will 

 not make way at once — though doubtless it would in time — for the new 

 adjustment. What is distinctive of this experience is the strenuous 

 persistence of the motor habit in spite of a considerable and conscious 

 effort to check it — a relation that in turn is significant for the compre- 

 hension of unusual and pronounced lapses. Another example of such 

 conflict of motor impulses may be arranged by attempting to write not 

 by direct visual guidance o'f the pencil, but by following the tracing of 

 the point (with the hand and pencil screened from direct sight) in a 

 mirror or system of mirrors. The new and unusual visual guidance 

 tells one to move the pencil in a given visible direction ; but this direc- 

 tion of seen movement has always meant a certain kind of c felt' move- 

 ment ; and when that type of ' felt ' movement is set into action it 

 proves to be, by the visual standard, completely and variously wrong. 

 The struggle between trying to push the pencil in the direction one 

 sees one ought to go, and also in the direction one feels one ought to 

 move, may become so intense as to be quite agonizing; and the attempt 

 must be abandoned as hopeless. Eemove the mirrors and use the nor- 

 mal visual guidance, or close the eyes and use the normal muscular 

 guidance, and the writing proceeds fluently, with but normal effort and 

 attention. Oppose the two factors of the normal combined and har- 

 monious synthesis, and confusion irresistible— a confusion, not of con- 

 scious intent, but of execution, of deep-seated automatic motor mechan- 

 isms — takes place. Likewise should it be noted that of all these modes 

 of guidance are we normally but vaguely aware; so much is this the 



