Abstract
Eye tracking studies suggest that refixations, fixations to locations previously visited, serve to recover information lost or missed during earlier exploration of a visual scene. These studies have largely ignored the role of precursor fixations, previous fixations on locations the eyes return to later. We consider the possibility that preparations to return later are already made during precursor fixations. This would mark precursor fixations as a special category of fixations, i.e., distinct in neural activity from other fixation categories such as refixations and fixations to locations visited only once. To capture the neural signals associated with fixation categories, we analyzed EEG and eye movement recorded simultaneously in a free-viewing contour search task. We developed a methodological pipeline involving regression-based deconvolution modeling, allowing our analyses to account for overlapping EEG responses due to the saccade sequence and other oculomotor covariates. We found that precursor fixations were preceded by the largest saccades among the fixation categories. Independently of the effect of saccade length, EEG amplitude was enhanced in precursor fixations compared to the other fixation categories 200-400 ms after fixation onsets, most noticeably over the occipital areas. We concluded that precursor fixations play a pivotal role in visual perception, marking the continuous occurrence of transitions between exploratory and exploitative modes of eye movement in natural viewing behavior.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
We have included a more detailed description of the eye-tracking study that considers precursor fixations ("to-be-revisited fixations" in their terminology) by Zhang et al. (2022). In the previous version, this excellent study was mentioned only briefly at the end of the Discussion because it was published just before our first submission a year ago and we inserted it at the last moment. Now we have given it more space.
