i8 T. L. Bolton and Donna L. Withey 



place in convergence, in lateral deviations, or in accommodation'' 

 of the eyes present a single serial order of change rather than 

 diverse orders. The contractions — the different degrees of con- 

 traction — may be looked upon as giving something more of the 

 same kind or as taking place in the same direction. In. the move- 

 ments of raising the arm or bending the finger, each step in fur- 

 ther contraction may involve the excitation of other muscles and 

 the stimulation of other tendons, joints, and skin areas. In the 

 eye movements the changes are due entirely to the excitation of 

 the muscle sheaths, increased tendinal strain, and the folding and 

 stretching of the skin and other sensitive tissues. But eye move- 

 ments give only space discriminations. Still greater and less , 

 movements must" change the strains and stresses about the eye in 

 a way that is not very different from the changes that are in- 

 duced in the arm muscles by lifting larger and smaller weights. 

 Certain combinations of stimulations mean different amounts of 

 excursion, and other combinations mean different amounts of re- 

 sistance overcome. Discrimination doubtless reduces itself at bot- 

 tom to one and the same process. 



Discrimination must be looked upon as a functional process, a 

 part of life activity. It is the process by which we make accurate 

 adjustment to our environments ; by which we come to know one 

 thing from another. Elementary discrimination is to be found in 

 the instincts. Every instinct is an inchoate discrimination of the 

 object that excites it. When these instinct performances become 

 conscious, as they do for the most part in men, they form per- 

 ceptions, and each perception implies making a distinction 

 between its object and all other objects taken together. Such dis- 

 criminations are perforce qualitative. When two objects are re- 

 acted to differently and the reactions are felt, the objects are felt 

 to be different. No object, then, is known until it has awakened 

 some form of reaction. The develo])mcnt of choices between ob- 

 jects belonging to the same class — those that have heretofore in- 

 vited the same reactions — shows the beginning of what subse- 

 quently becomes quantitative discrimination. The earliest form 

 of this is found in such instincts as the mating of birds and other 

 monogamous animals. In most of these cases the animals are so 



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