ACTIVITY IN HIGHER ANIMALS 161 



baby sees the bell, or in other words, the image of the bell 

 is formed upon the sensitive surface of the baby's eyes. 

 This image stimulates sensory nerves by which in turn 

 nervous impulses are conveyed to the brain where the 

 sensory impression is registered and stored as a memory. 

 This is pure memory of the appearance of a certain ob- 

 ject, and can have no meaning in the child's mind. At 

 another time the bell is rung, the child hears it and an- 

 other receptor is stimulated, another set of nervous im- 

 pulses is aroused, and in an entirely different part of the 

 brain a memory is registered, this being a memory of a 

 certain sound. Still later the child gets its hands upon 

 the bell and receives a series of sensations of touch which 

 are registered as memories in a still different part of the 

 brain. Thus the child has three separate and distinct 

 memories, all relating to the same object. By some pro- 

 cess within the brain which we do not at all understand, 

 these three related memories are associated. In other 

 words, the child perceives that they all belong together. 

 Thus it forms what we call an idea, which is a memory 

 of the bell as a whole. We must remember that the be- 

 ginning of this process in a baby is on a very small scale 

 and is probably not carried on very efficiently, so that it 

 may take the child some time to form satisfactory associa- 

 tions. We all know from our own observation, however, 

 that at a very early age the normal infant is found to be 

 equipped with a considerable range of very useful 

 associated memories. 



The Control of Activity in the Higher Animals. 

 (a) Reflex. — From what has been said in the paragraphs 

 above it should be clear that the activities of any animal 

 whose brain has the properties of memory and association 

 may be governed in at least two distinct ways. In the 

 first place, much of the activity may be purely reflex. 

 By this is meant that sensory stimulation may lead at 

 once and automatically to certain definite movements. 

 More of our own motions than we realize are of this 



