Regulation of eye movements and pupil size in natural scenes

The human visual environment is complex in its spatial, temporal, and spectral properties and, consequently, in the way it activates retinal photoreceptors. While laboratory studies have advanced our understanding of eye movements, how visual behavior unfolds in naturalistic settings remains less well characterized. In this study, we recorded eye movements and pupil size while participants viewed indoor and outdoor scenes under naturalistic conditions while remaining unaware of the eye-movement recordings. During the initial phase of viewing, saccade frequency, amplitude, and peak velocity were higher indoors and were accompanied by larger pupil size. Saccade metrics converged after this early exploration phase, whereas pupil size remained consistently larger indoors. Over the full viewing period, indoor and outdoor conditions exhibited distinct correlations between eye-movement metrics and subjective scene ratings. By minimizing task constraints and participant awareness of eye tracking while maintaining a controlled workflow, this study provides a dataset that reflects natural viewing behavior with reduced confounds. These findings suggest that eye-movement dynamics are particularly sensitive during initial scene exploration, whereas pupil size reflects persistent environmental differences. The present dataset offers a useful reference point for future research on eye movements in real-world contexts.