THE ART OF SCIENTIFIC INVESTIGATION 



Similarly in three of the anecdotes given at the beginning of 

 this chapter, the observation was followed by an intuition. 



Scientific observation 



We have seen how unreliable an observer's report of a complex 

 situation often is. Indeed, it is very difficult to observe and 

 describe accurately even simple phenomena. Scientific experi- 

 ments isolate certain events which are observed by the aid of 

 appropriate techniques and instruments which have been 

 developed because they are relatively free from error and have 

 been found to give reproducible results which are in accord 

 with the general body of scientific knowledge. Claude Bernard 

 distinguished two types of observation : (a) spontaneous or 

 passive observations which are unexpected; and (b) induced or 

 active observations which are deliberately sought, usually on 

 account of an hypothesis. It is the former in which we are 

 chiefly interested here. 



Eflfective spontaneous observation involves firstly noticing 

 some object or event. The thing noticed will only become 

 significant if the mind of the observer either consciously or 

 unconsciously relates it to some relevant knowledge or past 

 experience, or if in pondering on it subsequently he arrives at 

 some hypothesis. In the last section attention was called to the 

 fact that the mind is particularly sensitive to changes or differ- 

 ences. This is of use in scientific observation, but what is more 

 important and more difficult is to observe (in this instance mainly 

 a mental process) resemblances or correlations between things 

 that on the surface appeared quite unrelated. The quotation 

 from Trotter at the beginning of this chapter refers to this 

 point. It required the genius of Benjamin Franklin to see the 

 relationship between frictional electricity and lightning. Recently 

 veterinarians have recognised a disease of dogs which is manifest 

 by encephalitis and hardening of the foot pads. Many cases of 

 the disease have probably been seen in the past without anyone 

 having noticed the surprising association of the encephalitis with 

 the hard pads. 



One cannot observe everything closely, therefore one must 

 discriminate and try to select the significant. When practising 

 a branch of science, the " trained " observer deUberately looks 



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