Psychological Aspects of Ageing 211 



this is defined in tlie nsiial way as the interval which elapses 

 lietween the appearance of a stimulus or signal for movement 

 and the lieginnino- of the movement), but the resting; time, 

 or recovery time, between an adjustment which is in one 

 direction and an immediately following adjustment in a 

 different direction (Leonard, 1953). This has since been 

 confirmed in many other experiments, and, recently, in an 

 analysis of time-motion study films. It is the stationary items 

 in apparently continuous movement series that are most 

 liable to change. They are the constituents that are most 

 readily accelerated or decelerated. They tend to be drawn 

 out under the influence of certain drugs, of fatigue, and, almost 

 certainly, of increasing age. 



The interesting thing is that these stationary constituents 

 in a flow of movements, or of ideas, occur almost always, 

 perhaps always, where something specific about signals for 

 action has to be perceived, such as the shape, size, colour, 

 disposition and number of objects; or where, in what is 

 usually called "mental" skill, there is a shift from one topic 

 to another, or some new consideration has to be brought into 

 a process of thinking. This is to say that the most variable 

 elements in skill, and the ones that are most likely to be 

 affected adversely with increasing age, unless precautions are 

 taken, are just those that most indubitably demand central, 

 neurological activity and control. 



To have demonstrated an increasing importance of halts in 

 a flow of movements, or ideas, with increasing age is a step 

 in advance. But by itself it is not much of a step, and when 

 we try to go further we are at once brought up against diffi- 

 culties of interpretation which can be resolved only by more 

 experimentation. 



There is considerable evidence now that older people — I 

 mean broadly from the middle forties upwards — tend to look 

 both at what they are doing and at the signals for what they 

 are to do, in most kinds of bodily skill, when accurate and 

 rapid work is required, far more than younger people (Szafran, 

 1951). It may even be the case in general that increasing 



