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DISCUSSION 



Best: Dr. Welford, is there any evidence that the younger people 

 became bored during your experiments ? Is the falling off due not to lack 

 of ability but to the fact that they got tired of trying? 



Welford: It is possible that the youngest subjects in a few experiments 

 might have got a little bored, but that could not be said of the older, so 

 that any decline with age could hardly have been due to boredom. 

 Equally, however, it would be unsafe to argue that where an improve- 

 ment occurs with age, there are certain capacities which mature in 

 middle life rather than early on. 



Tunbridge: In reference to Kay's (1954) work don't you think that the 

 age difference could be very largely attributed to changes in eyesight? 

 You are testing alignment and your change begins to become apparent 

 at ages when you would get marked changes in vision and in the power 

 to accommodate. Surely you ought to split the sample on their visual 

 acuity and powers of adaptation ? A similar problem has arisen in testing 

 for dark adaptation in the determination of vitamin A deficiency. It 

 was found that the tests were quite unreliable after the age of 40, although 

 they were reliable in the younger age groups. 



