PROBLEMS FOR SOLUTION. 359 



action of external forces, such as seeing a light, 

 may be marked on the same paper by one of the 

 electrical signals. 



Here, then, there seems to be data for observations 

 as to the production of co-ordination by external 

 forces. 



To give an example in detail. Take a healthy 

 active infant, six months old. Adapt the motor 

 gauntlet to its hand, and make connections with 

 the other part of the apparatus. Take tracings 

 of the movements, and enumerate them and their 

 combinations. 



Now show the child an orange; let the light 

 reflected by the orange fall well within its field 

 of vision. Note the time of showing the orange 

 upon the tracing, by means of one of the electrical 

 signals. The co-ordinated movements of the infant's 

 fingers, wrist, and elbow are indicated by the 

 recording points. If all the fingers flex together 

 the combination of that special set of movements 

 will be recorded by the enumerator for that special 

 combination of finger movements. Kepeating the 

 experiment several times, we shall find out whether 

 this special combination of movements occurs more 

 frequently and certainly upon the stimulus of being 

 shown the orange, than it does in simple spon- 

 taneous movements of the fingers. A nurse would 

 say the child's attention is attracted by the orange 

 when it sees it If after many such trials on many 

 days the special movements of the hands occur with 

 greater certainty and quickness on seeing the orange, 

 the nurse would say that the infant has learnt to 



