Doğukan Nami Öztaş¹ (), Li L-Miao², Nihan Alp¹, Bilge Sayim²; ¹Sabanci University, Istanbul, ²École Normale Supérieure, PSL University, CNRS

In redundancy masking (RM), the number of items in repeating patterns is underreported. For example, three identical peripheral items are often reported as two. RM is associated with a radial spatial compression (the perceived radial extent of stimuli is reduced) and an inflated item-to-item spacing (the perceived distance between items is increased). Here, we hypothesized that RM would improve feature discrimination of the perceived items. In two experiments, we presented arrays of 3-5 identical, radially arranged bars with uniform spacing, randomly to the left or right of fixation. Observers reported the number of bars they perceived. In Experiment 1, a foveal probe containing the reported number of bars was presented, and observers adjusted both perceived width and spacing to match the presented array. In Experiment 2, a single-bar probe was presented, and observers adjusted its perceived width. Participants reported fewer items than presented, showing strong RM in both experiments. In Experiment 1, when the number of bars was underreported (RM-trials), observers reported wider –and more accurate– bar width, and larger –but less accurate– spacing than in No-RM-trials (correct number reports). In RM-trials, the reported horizontal extent of the arrays was reduced, showing radial compression of visual space. Importantly, perceived density was similar in RM-trials and No-RM-trials, and close to the presented stimulus density. In Experiment 2, the reported width difference between RM- and No-RM trials was reduced compared to Experiment 1, but still closer to the correct width in RM-trials. Together, our findings indicate that RM may enhance feature perception, possibly directly linked to spatial compression and accurate density perception observed under RM. It seems that RM preserves global density perception by jointly compressing space and the number of items. We suggest that RM is a mechanism by which the visual system compresses information while preserving critical stimulus features.

Acknowledgements: This study was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under the Grant Number 122N748.