Hold it there! Dynamic adjustment of fixation duration in visual search tasks

Eileen Kowler made very relevant contributions to our understanding of the fine-grain details of oculomotor performance in visual search tasks. She showed that saccadic timing could be strategically adjusted during search, considering aspects like fixation content or available visual information (Wu & Kowler, 2013). Following her steps, in this article we present additional results that support the idea of a dynamic adjustment of fixation durations. In three different experiments we registered eye movements while participants performed different visual search tasks. In two of the experiments only one visual search display was used, which was presented in all trials. In the third experiment half of the displays were repeated over trials. Eye movements in the three tasks showed similar patterns. In all experiments the number of fixations needed to find the target decreased significantly over repetitions. Interestingly, fixation durations differed depending on whether the fixation was on the target item or on other elements. Moreover, display repetition also had an effect on oculomotor performance: the duration of search fixations increased over repetitions while that of target fixations decreased. Amplitudes for search saccades also decreased over repetitions, while fixation locations gradually got closer to the target. These results provide interesting insights regarding oculomotor scanning strategies during search.