Biais perceptif et oculomoteur lors de la perception des visages : effets du vieillissement

Abstract : Previous studies demonstrated a left perceptual bias while looking at faces, observers using mainly information from the left side of a face (from the observer point of view) to make a judgment task. Such a bias is consistent with right hemisphere dominance for face processing and has been sometimes linked to a left gaze bias, i.e. more and longer fixations on the left side of the face (Butler et al., 2005; Megreya & Havard, 2011). In the course of aging, the left perceptual bias is still observed, but seems to require a longer exposure duration to faces (Butler & Harvey, 2008; Coolican et al., 2008). Here, in several experiments we recorded eye-movements during a gender judgment task, using normal and chimeric faces (made from two different half-faces of a male and a female) presented at the top, bottom, left or right relative to the central fixation point or at the center. Young and older participants performed the judgment task by remaining fixated on the fixation point or after executing one, two or three saccades. Even if young participants presented an overall left perceptual bias, it was not the case for older participants. Moreover, the perceptual bias depended on face position (a proximity bias was observed for lateral positions) and the number of allowed saccades (the perceptual bias was present when a saccade was executed). An important inter-individual variability was also observed. Indeed, some participants presented a left perceptual bias, while others presented a right perceptual bias or none at all. The gaze bias was also function of face position and is steady while growing older. This gaze bias seems to depend on the combination of two effects: the center-of-gravity effect (Bindemann et al., 2009) and the range effect (Kapoula, 1985). The saccade landing position was located around the center of the face, slightly oriented toward the initial fixation position. No apparent link between gaze and perceptual biases was found in any experiments, for both groups, meaning that a perceptual bias was not systematically coupled to saccades made toward the side of the face which was used to perform the gender judgment. Those results challenge the overall explanation put forward for those two biases that is the right hemisphere dominance for face processing.
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Hélène Samson. Biais perceptif et oculomoteur lors de la perception des visages : effets du vieillissement. Psychologie. Université René Descartes - Paris V, 2014. Français. ⟨NNT : 2014PA05H104⟩. ⟨tel-01067946⟩

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