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Sebastian Pannasch, Boris Velichkovsky; Testing processing mode within single visual fixations: Saccadic modulation of the distractor effect. Journal of Vision 2009;9(8):435. doi: 10.1167/9.8.435.
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In view of a variety of everyday tasks, it is highly implausible that all visual fixations fulfil the same role. Earlier we demonstrated that a combination of fixation duration and amplitude of related saccades strongly correlates with the probability of correct recognition of objects and events both in static and in dynamic scenes (Velichkovsky, Joos, Helmert, & Pannasch, 2005; Velichkovsky, Rothert, Kopf, Dornhoefer, & Joos, 2002). It has been variously reported that the presentation of sudden (visual) distractors influences not only the saccadic latency (e.g. Walker, Deubel, Schneider, & Findlay, 1997) but also the fixation duration in free visual exploration (e.g. Graupner, Velichkovsky, Pannasch, & Marx, 2007). In three experiments we investigated the amount of the distractor effect in relation to amplitudes of the preceding saccade. In Experiment 1, it is shown that retinotopically identical visual events occurring 100 ms after the onset of a fixation have significantly less influence on fixation duration if the amplitude of the previous saccade exceeds the parafoveal range (set on 5 deg of arc). Experiment 2 demonstrates that this difference diminishes for distractors of obvious biological value such as expanding motion patterns. In Experiment 3, we show that saccade amplitudes influence visual but not acoustic or haptic distractor effects. These results suggest an explanation in terms of a shifting balance of at least two modes of visual processing during a free viewing of meaningful visual images.
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