20 T. L. Bolton Old Donna L. Withey 



ment. Discrimination is bound up very closely with movement- 

 different movements meaning different things. One object is 

 dift'erent from another because it has something that the other has 

 not and this something invites another or a different movement 

 This is about the point to which we brought our discriminations 

 of pressure — one pressure is different from another because it 

 excites something that the other has left unaff"ected. 



The diff'erence between pressure sense and muscle sense is not 

 one of kind at all. The two are essentially only different aspects 

 of one and the same process, and that is the process of knowing 

 the differences between objects of the world. Tt is not, then, al 

 question whether these objects affect the skin surface, the tendons,! 

 the joints or muscles, and so bring out the reactions upon which] 

 the differences between things must finally rest. The point is 

 whether one object affects one sensitive part to bring out one re- 

 action and another object affects another part or the same part' 

 in a different manner that will bring out a different reaction. Our 

 local signs are just so many points which, when affected, do bring 

 out dift'erent reactions or tendencies to reaction. If one object 

 affects a certain group and another object aft'ects the same group 

 with some additions we say that these two diff"er intensively. 

 When movement is eliminated from the act of discriminating 

 weight, the stinndations which the weight sets up change in dif- 

 ferent directions and shift from one direction to another in suc- 

 cessive trials. xA.s movement is introduced, the stimulations are 

 more likely to vary in a single direction and are greater and more 

 constant in this direction for given amounts of difference in 

 stimuli. Each increased stimidus magnitude seems to add some 

 more of the same kind as that already there — a new point on the 

 scale. When the changes are confined to a single order, finer 

 discriminations may be made. 



The movement of lifting is initiated by a complex mental state 

 which is the result of the peripheral effects of a previous move- 

 ment that has accomplished the lift. When one is about to make 

 a lifting movement, the members that are to do the lifting are 

 adjusted to the positions which they have occupied in previous 

 liftings of weights whose indications are the same as the present 



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