MENTAL FUNCTION 413 



(instead of 0.180 second). This indicates the extent to which the inertia 

 of muscle (and nerve?) may be reduced by holding the organ in the 

 utmost tonic readiness. If one has to discriminate between colors in 

 the stimulus, the average reaction-time is over 0.300 second, while recog- 

 nition of a printed letter or short word requires 0.020 second longer. It 

 is found that in general a quantitative choice or judgment and choice 

 (between two stimuli, that is, of the same sort but different intensities) 

 is about 0.060 second. When it has become automatic the discrimina- 

 tion between two colors may require no more than 0.011 second, quality- 

 difference being more quickly perceived than quantity-difference. 



These reactions, it will have been observed, are under conditions 

 which represent the ordinary will-actions of every-day life reduced for 

 exact measurement to their very lowest terms. It has been objected 

 (as by Cattell) that experiments on fragments of actual will-process so 

 small as these have comparatively little practical use, however important 

 they may be theoretically. The movements of every-day life are im- 

 mensely complicated in every way, and fuse together so as to make a 

 medley of activities in muscle and nerve-center far beyond our present 

 power of comprehension or of measurement. Our consciousness derived 

 from them is at least correspondingly complex. 



HABIT AND INSTINCT. An instinct is essentially an hereditary im- 

 pulsive and unstudied habit concerned in the biological interests of the 

 individual or of the race. It is a complex variety of habit which needs 

 but little separate discussion here especially because the many varied 

 instinctive activities have in them only a minimum of attentive con- 

 sciousness. The mechanism by which the instincts are so carefully 

 bequeathed from parent to offspring century after century is part of the 

 vital faculty hidden in the body-protoplasm. Our search must be briefly 

 into the nature of habit, in which instinct partakes. 



Habit is a motion of very general significance in nearly all aspects of 

 the world. It means in the widest usage the adaptation of a material 

 to the activities of that material, and is therefore by no means confined 

 to organisms. Rain-water running down a hill-side gradually forms 

 grooves in the soil and leads to the formation of habitual water-courses. 

 Wild animals make paths through the forest to the ponds and springs. 

 Complicated machines run much better after a certain amount of use 

 has adapted the adjacent moving parts to each other and into a habit 

 of normal usage. In protoplasm, probably the most complex of sub- 

 stances, this universal adaptation is more complicated and consists not 

 only of action but of reaction not possible in inorganic machines. Owing 

 to the extreme plasticity of the material, organisms can work in a host of 

 different ways, each making an impression on the mechanism in propor- 

 tion to the number, the frequency, and the vigor of the activities con- 

 cerned. Thus, right-handedness unfortunately becomes a settled and 

 almost unbreakable habit in most persons' organisms before five years 

 have passed and simply because during the development of voluntary 

 movement the use of the left arm is neglected. What the traces are 



