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Attention searches nonuniformly in space and in time

Difficult search tasks are known to involve attentional resources, but the spatiotemporal behavior of attention remains unknown. Are multiple search targets processed in sequence or in parallel ? We developed an innovative methodology to solve this notoriously difficult problem. Observers performed a difficult search task during which two probes were flashed at varying delays. Performance in reporting probes at each location was considered a measure of attentional deployment. By solving a second-degree equation, we determined the probability of probe report at the most and least attended probe locations on each trial. Because these values differed significantly, we conclude that attention was focused on one stimulus or subgroup of stimuli at a time, and not divided uniformly among all search stimuli. Furthermore, this deployment was modulated periodically over time at ∼7 Hz. These results provide evidence for a nonuniform spatiotemporal deployment of attention during difficult search. .

Figure : Les performances d’identification de deux stimuli-sondes, flashés à des délais variables au cours d’une recherche visuelle, ont permis la résolution d’une équation du second degré déterminant la probabilité d’identifier correctement ces stimuli à la position la plus attendue (P1) et la moins attendue (P2) de l’espace visuel. Ces valeurs différaient significativement (différence supérieure à zéro) et variaient au cours du temps. Au cours de la recherche visuelle, l’attention se focalisait sur un stimulus (ou groupe de stimuli) à la fois, et n’était pas divisée uniformément sur tous les stimuli.

© Laura Dugué. Douglas McLelland. Mathilde Lajous. Rufin VanRullen

Mise à jour 17/12/2015