Speed and accuracy of movement and their changes with age

An experiment on the speed and accuracy of movement is reported in which subjects tapped to-and-fro with a pencil between two targets drawn on paper. The time taken was found to vary approximately, as in previous studies, with the logarithm of the ratio between the distance apart of the targets and their width. However, when speed was related to the actual scatters of shots on the targets instead of to the target widths, the results showed systematic and consistent departures from a linear relationship with the logarithm of the ratio between distance apart and the width of scatter. Two modifications to the formulation are discussed, one of which takes account of possible tremor effects, and the other of the possibility that visual control when ‘homing’ on a target may be slower than the control of movement designed to cover a given distance. Both modifications gave good fits to the observed results, but the second is preferred on grounds of consistency with the findings of other studies. The general pattern of results was followed for subjects in each decade of age from the twenties to the seventies. Performance improved in certain ways from the twenties to the thirties and forties, and thereafter declined with age.