Thesis defence : Olivier CLERC

From birth, infants are exposed to talking faces. Newborns will have to learn to process the information from them to be able to properly interact with their social partners. Face processing and language processing therefore develop quickly during infants’ first year of life. However, many infants have an exposure bias, whether for faces or for language: they are almost exclusively exposed to faces of their own type and to their native language. A consequence of this exposure bias is that infants will develop finer discrimination skills to process native stimuli than non-native stimuli. In the scientific literature, this phenomenon called perceptual narrowing has been highlighted many times in the context of language development and in the context of the development of face processing. The similar developmental trajectory of these two cognitive systems during the first year of life suggests interactions between these two systems. However, these interactions have not been investigated in detail.The aim of this thesis was to study the interactions between language and face processing during the first year of life.In a first study, we wanted to study the impact of face’s familiarity (established on race) on a phonemic matching task, on 3- and 9- month-old infants. 3-month-old infants do not seem to match a vowel with a corresponding speaker's video if the speaker is not of their own race. The results of this study indicate that from 3 months, infants process the audio-visual signal differently depending on the race of the face that produces it. In a second study, we wanted to evaluate the impact of face’s familiarity on the perception of the McGurk effect, on 6-, 9- and 12-month-old infants. Moreover, we wanted to see the robustness of this effect by studying it cross-culturally (in France and in Japan). We show that the sensitivity to this audio-visual illusion seems to be dependent on the race of the face. Moreover, our results and the japanese’s results differ, showing that sensitivity to the McGurk effect may be conditioned by the culture in which infants grow up. In a third study, we were interested in the impact of associations between face types and language types on the visual attention of 6-, 9- and 12-month-old infants. This study shows that at 3 months, some associations of languages and faces seem expected by infants and are consequently looked at longer. These associations are considered congruent since they do not disrupt the type of associations infants usually encounter in their environment. In a fourth study, we tested the impact of these associations on other-race face recognition by 9- and 12-month-old infants. We found that congruent associations help the recognition of individuals, while incongruent associations disturb the recognition of individuals.These studies support the idea that close interactions exist between language processing and face processing during infancy. Moreover, we show new perceptual narrowing’s consequences in infants under 9 months. We also show a new experimental way to modulate the impact of the perceptual narrowing. This thesis broadens our knowledge of perceptual narrowing and helps us to refine its definition.

Encadrement :
- Directeur de thèse : Olivier PASCALIS - olivier.pascalisuniv-grenoble-alpes.fr (olivier[dot]pascalis[at]univ-grenoble-alpes[dot]fr)
- Codirecteur : Hélène LOEVENBRUCK -helene.loevenbruckuniv-grenoble-alpes.fr (helene[dot]loevenbruck[at]univ-grenoble-alpes[dot]fr)

Keywords of the thesis: Face, Effect of another type, inter-linguistic, Infant, Perceptual narrowing

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