Distractor filtering in the visual attention domain: evidence for habituation of attentional capture.

In everyday life, we are constantly surrounded by a huge amount of information.Since our attentional resources are limited, we need to select just the stimuli that we want to process. Despite our voluntary attempt to select a precise information, it often occurs that a salient stimulus or event automatically captures our attention, regardless its irrelevance. The fact that we are immediately and unintentionally attracted by sudden visual onsets provides a clear advantage for our survival. However, in spite of that, the possibility to counteract visual distraction is fundamental for an efficient interaction with the environment, particularly when a salient but irrelevant stimulation repeatedly affects our visual system. And then, how can we resist from being continuously distracted by irrelevant repetitive onsets? The current work is aimed to explore the mechanisms that we use to filter irrelevant information, with a focus on habituation, an ancestral form of learning that has recently been associated to the decrement of attentional capture observed in several studies. This experience-dependent learning process is defined as a behavioral response decrement that results from repeated stimulation and that does not involve sensory or motor fatigue. I will first provide the reader with a general introduction (Chapter 1) concerning the visual attention field, with a particular emphasis on attentional capture and the filtering of irrelevant information. I will then (Chapter 2) try to disentangle the two main accounts concerning the nature of the distractor filtering, the first claiming that filtering is accomplished to shield target processing from interference (top-down inhibitory control hypothesis), and the second stating that the passive exposure to a repeating visual onset is sufficient to trigger learning-dependent mechanisms to filter the unwanted stimulation (habituation hypothesis). After providing strong evidence in favor of the latter account, I will then examine (Chapter 3) to what extent the filtering of irrelevant information that we achieve through the mechanisms underlying habituation is affected by contextual cues, showing that this kind of filtering is context-dependent. Finally (Chapter 4), motivated by the existence of a strong functional and anatomical link between attention and the oculomotor system, I will explore whether habituation affects also the oculomotor capture triggered by an onset distractor, showing that the execution of reflexive saccades is subject to habituation, while the programming component is not. Taken together, the results of the present work give a strong contribution to the attentional capture field in showing that both attentional and oculomotor capture are subject to habituation, that this form of learning is context-specific and that it occurs also when we are passively exposed to a visual irrelevant stimulus.