OBSERVATION 



observations. False observations may be due to illusions, where 

 the senses give wrong information to the mind, or the errors may 

 have their origin in the mind. 



Illustrations of optical illusions can be provided from various 

 geometrical figures (see, for example, George*^) and by distor- 

 tions caused by the refraction of light when it passes through 

 water, glass or heated air. Remarkable demonstrations of the 

 unreliability of visual observations are provided by the tricks 

 of " magicians " and conjurors. Another illustration of false 

 information arising from the sense organs is provided by placing 

 one hand in hot water and one in cold for a few moments and 

 then plunging them both into tepid water. A curious fallacy of 

 this nature was recorded by the ancient Greek historian, 

 Herodotus : 



" The water of this stream is lukewarm at early dawn. At the 

 time when the market fills it is much cooler; by noon it has 

 grown quite cold; at this time therefore they water their gardens. 

 As the afternoon advances, the coldness goes off, till, about 

 sunset the water is once more lukewarm." 



In all probability the temperature of the water remained constant 

 and the change noticed was due to the difference between water 

 and atmospheric temperatures as the latter changed. Fallacious 

 observations of a similar type can be shown to arise from illu- 

 sions associated with sound. 



The second class of error in registering and reporting observa- 

 tion has its origin in the mind itself Many of these errors can 

 be attributed to the fact that the mind has a trick of unconsciously 

 filling in gaps according to past experience, knowledge and con- 

 scious expectations. Goethe has said : 



" We see only what we know." 



" We are prone to see what lies behind our eyes rather than what 

 appears before them," an old saying goes. An illustration of this 

 is seen in the cinema film depicting a lion chasing a negro. The 

 camera shows now the lion pursuing, now the man fleeing, and 

 after several repetitions of this we finally see the lion leap on 

 something in the long grass. Even though the lion and the man 

 may have at no time appeared on the screen together, most 

 people in the audience are convinced they actually saw the lion 



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