Speed and Load Stress in a Sensori-Motor Skill

Experimental psychology has long been dominated by the proposition that a knowledge of sensory thresholds would provide a framework for the study of human behaviour. Some serious shortcomings of the traditional psychophysical methods for ascertaining these thresholds have been pointed out by Bartlett (1947), who stressed the fact that the discrete stimulus-response situation of psycho physical experiments can provide little information about the sensory processes involved in life, where the subject is dealing always with a series of stimuli. At the same time, psychology has been equally guilty of failing to recognize that under natural conditions perception of a single series of stimuli is not much more than a theoretical possibility. In fact, behaviour must be determined by the percep tion not only of concurrent series of stimuli in different sensory modes, but also of concurrent, but not necessarily related, series of stimuli in the same mode. Particularly one cannot assume that any one sensory threshold determines the framework of behaviour without taking into account the operation of the other thresholds which are almost certain to be present.