Stimulus properties and saccade metrics: When local features are more critical than global features.

Abstract

One major issue in the field of vision is how stimulus properties contribute to determine where the eyes move. Here, we examined the role of local versus global visual features in the computation of saccade metrics in the light of the well-known tendency for saccade to vary with the size of the stimuli. We used a saccade-target task in which we varied the properties of a visual distractor simultaneously displayed with the target stimulus. Both the size and the luminance contrast of the distractor were varied but the number of elementary features that composed the distractor was held constant. Our results showed that under such controls mean saccades' landing position remained unaffected by stimulus size irrespective of the level of luminance contrast. These findings suggest that the local visual features of a stimulus may be more critical than global features to specify a particular location to look at. These results are consistent with the notion that local features contribute to determine the amplitude and the width of the neuronal activity patterns associated with the visual stimulation and hence the computation of saccade metrics.