Abstract
In peripheral vision, humans have a better sensitivity to radial orientations (pointing towards the fovea) than to tangential ones (orthogonal to the fovea). We reasoned that due to these radial biases, objects perceived in peripheral vision may be encoded as if they were ‘filtered’ in the radial direction. Following this reasoning, humans should be better at identifying the face of their conspecifics along the horizontal meridian. These locations would facilitate the encoding of horizontal orientation, which is known to convey the most useful information for the recognition of face identity in foveal vision. To test this hypothesis, we instructed participants to recognize upright and inverted faces appearing briefly either at the fovea, or at 8° of eccentricity along the horizontal or vertical meridian. We measured face recognition as a function of stimulus visibility by parametrically scrambling stimulus phase. We then compared the psychometric functions for upright and inverted faces. A shift between the two functions, i.e. the face inversion effect, was taken here as a marker of the ‘specificity’ of face identity processing. We found a significant inversion effect along the horizontal meridian. This effect was comparable to that of the fovea, suggesting the engagement of face-specialized mechanisms at both locations. However, the inversion effect strongly reduced in magnitude when faces were presented on the vertical meridian, suggesting that the face processing system was disrupted through the reduction in the horizontal information most diagnostic to identity encoding. This result supports the hypothesis that radial biases in peripheral vision modulate the encoding of face identity cues by limiting access to oriented content.