J.— PSYCHOLOGY. 185 



(Yerkes noted that his chimpanzee would frequently laugh in response to 

 favourite foods.) 



(ii) The next occurrence of laughter was in response to laughter of 

 mother or father at ten weeks, followed by laughter even at a smile 

 (eighteen weeks). 



(iii) The third occurrence was caused by tickling, also at ten weeks. 



(iv) The fourth type is laughter at the sight of a bright or pleasing 

 object (twelve weeks). 



(v) Next we come to laughter at a simple shock or surprise (eighteen 

 weeks). Thus B laughed (three times) when I tore a newspaper — a sound 

 which had previously caused an apparent start of fear. By this age (four 

 months) laughter was very frequent. (Gesell found that 85 per cent, of 

 the babies he tested could laugh at the age of four months.) 



(vi) Mere repetition of a stimulus, or our imitating actions of B seemed 

 to be enough to cause laughter at about six months. The comic efEect of 

 mere repetition remains long in operation ; a comedian says ' Now we 

 shan't be long,' and no one takes any notice. He says it again and people 

 smile ; again, and there is a roar of laughter. It is the six-months-old 

 baby reaction. 



(vii) The next cause of laughter in B (seven months) was the unfamiliar 

 and unusual in the midst of the familiar — a ' shock ' of a mere intellectual 

 surprise, e.g. my falsetto voice, or the sight of his mother in a paper cocked 

 hat. 



(viii) At seven months there were also suggestions of laughter at mere 

 recognition, but of this I was not certain. 



(ix) Between eight months and twelve months another cause of 

 laughter appeared — the successful accomplishment of some new activity, 

 e.g. standing alone. 



(x) The sight of the mild discomfiture of another is a well-known cause 

 of laughter. McDougall, indeed, bases his theory of laughter on this 

 phenomenon, suggesting that we laugh in order to avoid the contrary 

 feeling of sympathy which would prove too exhausting if too frequently 

 experienced. 



It is notable that as many as eight or nine different causes of laughter 

 were observed in B before anything of the nature of this last type was 

 seen. Only in the seventeenth month did I note laughter of this type in B, 

 who gave loud roars of laughter when his mother tumbled down a grass 

 bank. It must be admitted, however, that occasions on which B would 

 have an opportunity of seeing such slight discomfiture of others were rare. 

 Possibly, therefore, the date of this type of laughter response should be 

 considerably earlier. A sufficient number of examples of earlier kinds 

 of laughter have, however, been given to indicate how very varied the 

 original causes of laughter are and how the earliest appearances depend 

 on the joj^ul satisfaction of elementary needs. 



The fundamental nature of thought processes is another problem on 

 which I believe the study of early child psychology will ultimately throw 

 a flood of light. The intimate association of thought with language enables 

 one to obtain material with relative ease. Far more difficult, however, is 

 the interpretation of the words spoken by the child. We must throughout 



