The effect of isoluminant and isochromatic stimuli on latency and amplitude of saccades

When two stimuli are presented in different positions successively at short time intervals saccadic eye movements are usually directed at intermediate positions. This phenomenon of "averaging" of saccadic eye movements has been studied in responses to double-step target displacements in different stimulus conditions. In these conditions isoluminant and isochromatic stimuli were used with variable contrast and at different background luminances. Although the critical duration of temporal summation differed considerably in these stimulus conditions the duration of the phenomenon of "averaging" remained the same in all conditions. This indicates that temporal properties of the sensory system are not the prime cause of "averaging". Moreover, the onset time of "averaging" relative to the second target displacement turned out to be highly correlated with the mean latency of saccades in the different conditions. The implications of the results for models of oculomotor control are discussed.