Speed and Load Stress as Determinants of Performance in a Time Sharing Task

The effects of speed and load stress were investigated in a task where operators responded to moving visual stimuli that entered critical zones in each of three visual displays. As expected, increases in either speed or load stress resulted in significantly poorer performance. More importantly, the effects of speed stress were made apparent by a speed by load stress interaction. At the lowest level of load stress where the operator was only required to attend to one display, increases in speed stress did not have any apparent effect. However, as load stress increased to two displays and especially to three displays, increases in speed stress had a significant negative impact on performance. Data concerning the timing of these responses further supported this analysis. It appears that future generalizations about the effects of speed stress must consider the level of load stress present in the task.