214 General Discussion 



Bartlett: For the most part, our initial work was carried out with 

 skills that involved the notion of tracking. You have an object which is 

 moving in a given direction, and its movement either has to be pro- 

 gressively followed or controlled in some way. Then there was an ex:- 

 tension from this, and the things that I have spoken of have been tried 

 out with a considerable variety of bodily skills, with a good many mental 

 skills involving memory and anticipation processes proper, and they 

 have also been taken into the factory and applied to repetitive activities 

 such as are involved in assembly work and conveyor belt work. The 

 same features have occurred over and over again. The thing which is 

 variable is the interval between a movement that is required to locate 

 something in one position, let us say, and then take it from that position 

 to another. The same thing occurs in connection with a lot of skills in 

 games, which we have studied. It also occurs in a good many operative 

 procedures in the laboratory, where what you have got to do is to locate 

 a particular tiling that you want to do something about and then move 

 it into a given position in relation to something else. A skilled process 

 always involves a sequence of movements, mental or physical, inter- 

 spersed with changes of direction, and it is the halts between changes 

 of direction that are the most unstable feature; it is these which are 

 most affected when what we call tiredness or fatigue sets in, which 

 are most influenced by drugs, and which become more marked with 

 increasing age. 



Franklin: Is there any difference between the sexes? 



Bartlett: None at all, as far as we know, but most of these experiments 

 have been done with men in the factory and in the laboratory. But 

 wherever we have had older women they have shown the same character- 

 istics, and there doesn't seem to be any important difference at all. 



Lewis: Have any of these studies been carried out on people whose 

 mental powers were obviously failing — perhaps in the early stage of 

 dementia? 



Bartlett: No, we try to keep away from that as far as possible and to 

 have a range of people who would satisfy the requirements of normal 

 mentality. We have kept off people with special disabilities because we 

 think that complicates the picture at this stage. I think it possible that 

 you would have these things happening, but a good many other things 

 superimposed on them as well. 



Lewis: I was wondering whether, since these are central happenings, 

 they would be more evident in people with dementia. 



Bartlett: Yes, it could be, but I don't know about that. 



Franklin: How far does the ageing of the eye come into this? 



Bartlett: Since we have tried to keep to people with normal eyesight, 

 we have no evidence that anytliing very much is dependent upon visual 

 responses as such, except that the optimum distance of the signal for 

 action from the viewing point will tend to go a bit further away. 



Shock: Do you think that the way to look for age changes is in an 

 activity that is well practised in the individual, one that he has done 

 repeatedly? Or are you more likely to see age differences when you pre- 

 sent him with an entirely new activity? 



