The Visual Stimulus for Saccadic Eye Movements in Human Observers

Three experiments are reported in which the salience of visual stimuli is assessed by finding which of two competing peripheral stimuli elicit a saccade when both are presented simultaneously with the use of a paradigm due to Lévy-Schoen. The first experiment shows how salience is affected by position in the visual field. A strong effect of retinal eccentricity is found which is compared with the cortical magnification factor. Additionally directional biases occur. The second experiment shows that temporal change appears to be significant in eliciting a saccade rather than any specific properties related to movement. The third experiment shows that contour at high spatial frequencies does not affect salience. An area of 4 cycles deg-1 high-contrast square-wave grating possesses the same salience as an equivalent area with identical, constant, space average luminance. Taken together, the results suggest that salience might be accountable for in terms of the activation of transient channels in the visual system.