158 Habituation 



is linked to I, and III to II, and IV to III, so that 

 one follows or accompanies the other with great 

 facility. As they say, "paths of low resistance" are 

 established in the nervous system. The linkage be- 

 comes stronger in proportion to the number of repe- 

 titions, plus in many cases the influence of certain 

 psychological factors, such as the pleasure of suc- 

 cess and the determination to succeed. The path 

 becomes more beaten the more it is trodden. Habitua- 

 tion means the making of paths, the forging of 

 linkages. 



There are habits and habits, differing in com- 

 plexity and in origin. There are simple one-act 

 habits in which the creature learns to associate a par- 

 ticular signal with a particular experience and acts 

 accordingly with ever-increasing facility. At the 

 sound of a particular bell the cat darts upstairs to 

 a room where it is fed ; but that is simpler than what 

 we see when a well-instructed dog obeys the command 

 to go to a certain room and fetch its master's slippers 

 or newspaper or walking-stick. After a few lessons 

 a frog learns to avoid disagreeable objects, such as 

 hairy caterpillars or doped worms; and the habit 

 lasts for a week or more. Habits that are in a line with 

 the creature's everyday behavior are most quickly 

 learned, but the acquisition of very artificial habits 

 is quite common. Triplett divided an aquarium into 

 two with a glass screen, and placed minnows in the 

 one compartment and two perch in the other. For a 

 month the perch continued butting their beads 

 against the glass in obeying the impulse to seize the 



