Does radial bias contribute to fast saccades toward faces in the periphery?

Saccadic choice studies have shown that humans initiate faster saccades toward faces than other visual categories. Here, we tested whether the saccadic advantage for faces observed in past studies is partly due to stimuli being typically presented along the horizontal meridian (HM). Our previous work suggests that the radial bias along the HM facilitates access to the horizontal structure of faces, which optimally drives human face-specialized processing. We expected to corroborate the saccadic advantage for faces along the HM, where the radial bias facilitates access to horizontal content, and to observe a reduction of this advantage along the vertical meridian (VM), especially in participants showing a strong horizontal tuning for face recognition. Fifty participants performed a saccadic choice task targeting faces or vehicles presented at 15° eccentricity along the HM and VM. We also assessed the strength of the radial bias and the horizontal tuning for face identity recognition in each individual. As expected, saccades were faster and more accurate toward faces than vehicles; they were also faster along the HM than the VM. Contrary to our hypothesis, the saccadic face advantage did not differ between meridians, suggesting the robustness of face saccadic advantage. However, the saccadic face advantage along the VM correlated with the strength of the horizontal tuning of face identity recognition. Additionally, the radial bias predicted saccade latency toward faces along the HM. These findings indicate that low-level radial biases and high-level face-specialized mechanisms independently contribute to distinct functional aspects of the ultra-fast saccadic responses toward faces.