SACCADIC INHIBITION IN COMPLEX VISUAL TASKS

Several gaze contingent studies that used a fixed delay between physical eye movements and a display change documented a dip in the fixation duration distributions (e.g., Blanchard et al. 1984; McConkie et al. 1985; van Diepen et al. 1995). In a study by van Diepen et al. (1995), a moving mask paradigm was employed in which subjects searched line drawings of everyday scenes for non-objects. The appearance of the mask was delayed relative to the end of a saccade (beginning of fixation) by 17, 46, 76 or 121 msec. All fixation duration distributions in the masking conditions exhibited a dip with longer masking delays resulting in the dip occurring at longer fixation durations. In contrast, a no-mask condition did not produce a dip. Similar effects in reading were reported by Blanchard et al. (1984), and McConkie et al. (1985). In both these studies the text was masked at a fixed delay from the end of the saccade, and the fixation duration distributions exhibited dips. McConkie et al. (1992) interpreted these dips as reflecting a disruption to automatic, parallel encoding or registration processes that are time locked to the onset of the visual pattern on the retina. Processing disruption causes an eye movement disruption after a constant transmission delay in the neural system.