December 2022
Volume 22, Issue 14
Open Access
Vision Sciences Society Annual Meeting Abstract  |   December 2022
Stimulus size modulates idiosyncratic neural face identity discrimination
Author Affiliations
  • Lisa Stacchi
    University of Fribourg
  • Roberto Caldara
    University of Fribourg
Journal of Vision December 2022, Vol.22, 3473. doi:
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      Lisa Stacchi, Roberto Caldara; Stimulus size modulates idiosyncratic neural face identity discrimination. Journal of Vision 2022;22(14):3473.

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      © ARVO (1962-2015); The Authors (2016-present)

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Human observers show reliable individual differences in neural identity discrimination (FID) across viewing positions when faces are covering the visual angle typical of natural social interactions (80-100cm - ~12°-14°). These distinct patterns of neural responses directly relate to observers’ idiosyncratic fixation strategies. Although these individual differences are a unique source of information, they can also be difficult to take into considerations when it is not possible to test a high number of conditions. To address this potential issue, we explored whether reducing stimulus size would help decrease such inter-individual variations. We parametrically manipulated the size of face stimuli (3°, 5°, 6.7°, 8.5°, and 12°) as well as the fixation location (left eye, right eye, just below the nasion, nose, and mouth) while recording electrophysiological responses. Same identity faces were presented at a constant frequency rate with the periodically interleaving of different face identities to trigger an objective and implicit index of neural FID. Our data obtained from thirty-five healthy young Caucasian adults show the presence of robust and consistent individual differences in neural face identity discrimination across viewing positions for all sizes. Nevertheless, FID was optimal for a larger number of observers when faces subtended 6.7° of visual angle and fixation was just below the nasion. This condition is the most suited to reduce the natural variations in neural FID patterns observed across observers. Crucially, this observation establishes an important benchmark for future FID studies where it is not possible to assess and control the idiosyncrasies of each participant.


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