M Pilar Aivar¹, Laura Cepero¹, Miguel A Vadillo¹, Victoria Plaza¹; ¹Universidad Autónoma de Madrid

The proposal of the functional viewing field (FVF) has highlighted the relevance of studying eye movements to better characterize visual search processes (Hulleman & Olivers, 2017; Wolfe, 2021). Still, it is often assumed that the FVF has both a constant size and a constant processing time (Shi, Zang & Geyer, 2017). Very few studies have investigated whether fixation durations vary during visual search depending on the repetition of the display or the kind of element that is fixated. Here, we present the results of three experiments in which we recorded eye movements while participants performed different types of visual search tasks. In all experiments some aspects of the visual search display were repeated over trials while other aspects were irrelevant to the task. In the first study we used a comparative visual search paradigm: participants had to find the only item that differed between both sides of the screen. Display configurations were repeated during the experiment. In the second study we employed a repeated search paradigm, presenting different targets but the same search display in all trials. In the third study we employed a contextual cueing paradigm, manipulating the number of relevant and irrelevant distractors. Half of the configurations were repeated, intermixed with newly generated configurations. Eye movements in these three tasks showed interesting 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 had an effect on fixation durations: search fixations increased duration while target fixations decreased duration over repetitions. These results suggest a dynamic adjustment of fixation duration which might be related to the size of the FVF and provide some insights regarding oculomotor scanning strategies during search.

Acknowledgements: Research supported by grants PID2020-118583GB-I00 and PID2021-125162NB-I00.