150 A. T. Welford 



means of factory records or by direct observation and measure- 

 ment of industrial performance. 



Four topics will especially be considered : 



(1) The relative merits of these different sources of data. 



(2) Problems arising from the complexity of the human 

 "mechanism". 



(3) Questions of motivation — are younger and older sub- 

 jects equally willing to try their best? 



(4) Certain other problems arising from the need to com- 

 pare subjects of different ages or test the same individ- 

 uals more than once. 



(1) Experiments and Industrial Studies 



Experiments are well recognized as probably the most 

 powerful tool we possess for the study of human performance. 

 They essentially use tasks specially constructed to bring out 

 some particular aspect of performance, such as speed or 

 accuracy of movement or ability to perform one or other type 

 of intellectual operation. The task may take any of an almost 

 infinite variety of forms from drawing lines on paper or sorting 

 a pack of cards to simulations of high-grade skills such as 

 flying an aircraft or driving a car which involve substantial 

 and elaborate apparatus. Whether simple or complex they 

 aim at obtaining a sample of the subject's performance under 

 controlled conditions where a precise record can be taken for 

 subsequent analysis. 



One important limitation of experiments is that it is seldom 

 possible to continue them for a long time — usually a few hours 

 is the maximum and in most cases about half an hour is all 

 that can reasonably be demanded of a subject. This gives 

 rise to two opposing objections. The first is that if older 

 people are less resistant to fatigue than younger, they might 

 be able to maintain a performance for a short period at a 

 level which would be impossible over a longer working spell, 

 and the experiment would thus unduly favour older people. 



