METHODOLOGICAL PROBLEMS IN THE STUDY 



OF CHANGES IN HUMAN PERFORMANCE 



WITH AGE 



A. T. Welford 



The Psychological Laboratory, Cambridge 



It is relatively easy in principle to obtain information about 

 changes of performance with age, but to gain an understanding 

 of the nature and causes of these changes is a matter of un- 

 usual difficulty. This is due partly to problems inherent in all 

 psychological research and partly to certain of these being 

 intensified when age changes are studied. We shall not here be 

 concerned with large-scale fact-finding investigations such as 

 surveys of the numbers of men in different industries or on 

 various grades of work. These have been used in the attempt 

 to study human capacity in relation to age and, when carried 

 on by personal enquiry rather than by circulated question- 

 naires, are of value as indicators of issues for more intensive 

 study and as checks on theories formulated by such study. 

 They are, however, ill-adapted to provide a thorough under- 

 standing of changes of performance with age leading to 

 theoretical explanations or detailed solutions of practical 

 problems — their use for these purposes is not impossible but 

 tends to be extremely laborious and expensive. The reason is 

 that surveys which are easy to make are so only because they 

 deal with whole industries or factories or with classes of work 

 such as skilled, semi-skilled and unskilled, whereas the dif- 

 ferences of human demand are between individual operations, 

 of which many making a variety of different demands are 

 usually included in the larger groupings. We shall instead 

 concentrate on the methods of more intensive studies consist- 

 ing firstly of experiments, usually conducted in a laboratory, 

 and secondly of studies of actual work in industry either by 



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