The impact on emotion classification performance and gaze behavior of foveal versus extrafoveal processing of facial features.

Abstract

At normal interpersonal distances all features of a face cannot fall within one's fovea simultaneously. Given that certain facial features are differentially informative of different emotions, does the ability to identify facially expressed emotions vary according to the feature fixated and do saccades preferentially seek diagnostic features? Previous findings are equivocal. We presented faces for a brief time, insufficient for a saccade, at a spatial position that guaranteed that a given feature-an eye, cheek, the central brow, or mouth-fell at the fovea. Across two experiments, observers were more accurate and faster at discriminating angry expressions when the high spatial-frequency information of the brow was projected to their fovea than when one or other cheek or eye was. Performance in classifying fear and happiness (Experiment 1) was not influenced by whether the most informative features (eyes and mouth, respectively) were projected foveally or extrafoveally. Observers more accurately distinguished between fearful and surprised expressions (Experiment 2) when the mouth was projected to the fovea. Reflexive first saccades tended towards the left and center of the face rather than preferentially targeting emotion-distinguishing features. These results reflect the integration of task-relevant information across the face constrained by the differences between foveal and extrafoveal processing (Peterson & Eckstein, 2012).

Foveal processing of emotion-informative facial features

“…L. Smith & Merlusca, 2014)? We also here extend our previous work (Atkinson & Smithson, 2020) by examining the direction and paths of reflexive first saccades triggered by the onset of the briefly presented face, to further test the hypothesis that those saccades target emotion-informative facial features. Although we found no support for this hypothesis in our previous study, additional tests of this hypothesis with different combinations of emotions are warranted.…”

“…Yet, in the context of the brief-fixation paradigm, our previous study (Atkinson & Smithson, 2020) did not find any evidence to indicate that reflexive first saccades preferentially target emotion-distinguishing facial features. Although we replicated the key finding of more upward saccades from enforced fixation on the mouth than downward saccades from enforced fixation on the eyes, the modulation of this effect by the expressed emotion was evident in our first experiment, in which angry, fearful, happy and neutral faces were used (the effect was evident for angry and neutral faces, less so for fearful faces, and not at all for happy faces), but not in our second experiment, in which angry, fearful, surprised and neutral faces were used.…”

“…In this experiment, we used the same modified version of Gamer and Büchel's (2009) brief-fixation paradigm used by Atkinson and Smithson (2020), here with angry, fearful surprised and sad expressions, to test two hypotheses: (1) A single fixation on an emotiondistinguishing facial feature will enhance emotion identification performance compared to when another part of the face is fixated (and thus the emotion-informative feature is projected to extrafoveal retina). (2) Under these task conditions, observers' reflexive first saccades from initial fixation on the face will preferentially target emotion-distinguishing facial features when those features are not already fixated.…”

“…In this study, we investigate the differential contributions of foveal and extrafoveal visual processing of facial features to the identification of facially expressed emotions (see also e.g., Atkinson & Smithson, 2020). The fovea, a small region of the retina that corresponds to the central 1.7° of the visual field (Wandell, 1995), is preferentially specialized for processing fine spatial detail.…”

“…In a previous study, we showed that emotion classification performance varies according to which emotion-informative facial feature is fixated (Atkinson & Smithson, 2020). In that study, we used a slightly modified version of a 'brief-fixation paradigm' developed by Gamer and Büchel (2009), in which faces were presented for 80 ms, a time insufficient for a saccade, at a spatial position that guaranteed that a given feature -the left or right eye, the left or right cheek, the central brow, or mouth -fell at the fovea.…”