Guiping Zheng¹ (), Rong Jiang¹, Ke Zhou², Shuai Chang³, Xinping Yu³, Liqin Zhou², Ming Meng¹; ¹Philosophy and Social Science Laboratory of Reading and Development in Children and Adolescents (South China Normal University), School of Psychology, South China Normal University, Guangzhou 510631, China., ²Beijing Key Laboratory of Applied Experimental Psychology, National Demonstration Center for Experimental Psychology Education (Beijing Normal University), Faculty of Psychology, Beijing Normal University, Beijing 100875, China., ³State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou 510060, China.

The Multiple Object Tracking (MOT) paradigm is widely used to explore the allocation and deployment of attention to multiple moving objects in dynamic scenes. Albeit extensive, previous research has led to conflicting views regarding the initial processing stage at which attentional modulation influences MOT — specifically, whether it occurs in early visual regions or at later processing stages. To address this question, we employed a dichoptic MOT paradigm, where 0 to 4 tracking targets and 4 distractors were presented to one eye, and the remaining targets (totaling 4) and another 4 distractors to the other eye. In a switch condition, the retinal projection of target stimuli swapped once between eyes, while in a non-switch control condition, targets presentation remained within the same eye, and visual perception maintained consistent across both conditions. In Experiment 1, such interocular target switching significantly impaired tracking performance when stimuli moved rapidly, revealing a monocular advantage for MOT. Experiment 2 examined whether this effect extended to distractor switching and found no significant results, suggesting that the monocular advantage might be specific to target switching. In Experiments 3a-3c, we introduced jittering of stimulus contrast to control for dichoptic contrast sensitivity differences, and further investigated how different proportions of the target allocation between the two eyes affected the magnitude of the monocular advantage. We found the monocular advantage was amplified when targets were equally distributed between the two eyes, with tracking accuracy in the switch condition decreasing by over 40% compared to the non-switch condition. These findings suggest that attentional modulation in MOT occurs at an early stage of visual processing, i.e. at or before monocular processing in the primary visual area (V1), and may involve subcortical structures, such as the lateral geniculate nucleus (LGN), which are mostly monocular.

Acknowledgements: This work is supported by (1) the National Nature Science Foundation of China (Grant No. 31871136), (2) the Science and Technology Ministry of China (Grant No. 2021ZD0204200), and (3) the Sino-German Center for Research Promotion (Grant No. M-0705).