Surprise, surprise: Two distinct components in the visually evoked distractor effect

Abstract

The distractor effect is an inhibition of saccades shortly after a sudden visual event. It has been explained both as an oculomotor reflex and as a manifestation of the orienting response. To clarify which explanation is more appropriate, we investigated a possible habituation of this effect. Visual and auditory distractors were presented at gaze-contingent intervals during the perception of meaningful pictures. Both reflexlike and modifiable components were present in the visual distractor effect, with latencies of about 110 and 180 ms, respectively. The influence of visual and auditory distractors on saccades preceded the earliest changes in cortical ERPs. Only for long-term habituation in the visual modality was a correlation with ERPs (N1) found.

On the control of visual fixation durations in free viewing of complex images

“…2b, gaps in the fixation distributions represent the distractor influence. The timing of this inhibition is in line with previous reports (Graupner et al, 2007;Reingold & Stampe, 2004). The distribution of fixation durations can be characterized by three clusters: First, fixations that are terminated within 100 ms after the distractor onset compose the unaffected cluster, since there is not enough time for distractors to influence the fixation.…”

“…Sokolov, 1963). The latter view is supported by the fact that gaze-contingent distractors of different modalities have revealed habituation-like processes in eye movements and in cortical event-related potentials (ERPs; Graupner, Velichkovsky, Pannasch, & Marx, 2007;Pannasch et al, 2001;). …”

“…In addition, the use of paintings allowed us to directly compare our results with those of previous work (Graupner et al, 2007;. Stimuli were displayed with a size of 1,024 × 768 pixels.…”

“…To alternatively examine the distractor effect with respect to the different distractor latencies and durations, baseline fixation durations were subtracted from the fixation durations of the distractor conditions; the resulting difference values represent the prolongation of the fixation due to the shown distractor (Graupner et al, 2007). Additionally, distractor fixations were classified as either ambient or focal on the basis of the preceding saccade amplitude (Pannasch & Velichkovsky, 2009).…”

“…This presentation interval was selected in accordance with previous work (cf. Graupner et al, 2007;Pannasch & Velichkovsky, 2009) in order to ensure that distractors did not become predictable and to acquire enough unaffected fixations to create a baseline. Distractors were triggered by the fixation onset, with an onset latency of either 100 or 200 ms; they remained visible for 100, 200, or 300 ms and were centered on the coordinates of the actual fixation.…”