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Abstract

While eye movement behaviour in well-constrained laboratory studies is very well understood, we know much less about eye movements under naturalistic conditions. Here, we created a benchmark dataset for naturalistic free-viewing, aiming to investigate differences in saccade, fixation and pupil size metrics between indoor and outdoor environments. Using a head-mounted wearable eye tracker (Tobii Glasses Pro 3), participants engaged in a naturalistic free-viewing task (Kay et al., 2023).They viewed six diverse indoor and outdoor scenes while withholding information about the nature of the experiment from the participants (n=18, 13 female; mean age 24.2 years). For each scene, we recorded eye movements during a 4- minute measurement interval while the light metrics of the scenes were concurrently recorded using a spectroradiometer. After each measurement, we also asked participants to rate the scene in terms of its beauty, brightness, and complexity, and rate their sleepiness. Light levels of indoor scenes were significantly lower (520.14±351.16 photopic lux) than those of outdoor scenes (9437.56±8822.15 ). Pupil size was substantially larger in indoor (2.88±0.71 mm) compared to outdoor conditions (2.07±0.32 mm). We found no significant differences in any of the eye movement metrics. In an exploratory analysis, we found a complex landscape of correlations between various eye movement, pupil and light metrics. We found no significant differences in naturalistic free- viewing of quantitatively and qualitatively different outdoor and indoor scenes. Our data set can serve as a benchmark for future eye movement studies.