Object groups mutually bias each other’s perceived average size, as evidenced by neural and behavioural data

The human visual system simultaneously computes summary statistics of object features, such as average size, across groups of objects. Evidence suggests that summary statistics across groups of objects (ensembles) are not independent but influence one another. We investigated whether an ensemble’s average size affects the perceived average size of another ensemble, and whether such changes are reflected in altered activation patterns in the visual cortex.

Distractor ensembles’ average sizes altered the perceived average size of target ensembles in a contrast-like manner: Large distractor ensembles decreased the target ensembles’ perceived average sizes; conversely, smaller distractor ensembles increased target ensembles’ perceived average sizes. These contrast effects were reflected in more activated voxels in retinotopic regions when target ensembles were perceived as larger. Distractor ensembles’ voxel counts were similarly modulated by target ensembles’ average size, suggesting their perceived average size was also altered.

Additionally, individual differences in the magnitude of the ensemble-size contrast effect covaried with activation in higher-level regions, including the left intraparietal sulcus (IPS) and middle temporal gyrus (MTG). Together, these findings suggest that ensemble summary statistics are contrasted, resulting in changes in perceived size and altered retinotopic activation pattern, with involvement of a network including left IPS and left MTG. Open access publication funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 491111487.

GRF gratefully acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) (Project-ID 431549029—SFB 1451). The funders have/had no role in the decision to publish or the preparation of the manuscript. We are grateful to our colleagues from the Institute of Neuroscience and Medicine for many valuable discussions.

This work was supported by Forschungszentrum Jülich GmbH. Besides, GRF gratefully acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) (Project-ID 431549029—SFB 1451). Cognitive Neuroscience, Institute of Neuroscience and Medicine (INM-3), Forschungszentrum Jülich GmbH, Leo-Brand-Str. 5, 52425, Jülich, Germany Elif Memis, Gereon R.

Fink & Ralph Weidner Department of Neurology, University Hospital Cologne, Cologne University, Kerpener Str. 62, 50937, Köln, Germany The authors declare no competing interests. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.