Human infants must rapidly develop the ability to perceive conspecifics across the senses to engage in social interaction. In this concert of the senses, olfaction is an early-maturing sense and primary medium of social communication from birth onwards. In contrast, human vision is poor at birth and follows a protracted development over the first year of life. Yet, infants already categorize a variety of visual stimuli as faces at a few months of age. Does olfaction foster face categorization in the developing visual system? In this talk, I will address this issue through a series of experiments using scalp electroencephalography (EEG), and demonstrate that one of the most relevant social odors for young infants, the mother’s body odor, shapes face categorization in their brain. I will show that maternal odor enhances face-selective neural activity over the right occipital cortex at 4 months, this effect being absent for nonface objects, except for objects that can be perceived as faces (eliciting face pareidolia in adults). I will also illustrate how the facilitating effect of maternal odor gradually declines between 4 and 12 months as face categorization becomes more efficient by itself. Finally, I will reveal that the odor effect fades in the 4-month-old brain when face categorization is made less demanding for the young visual system. Altogether, these findings will disclose how the developing brain builds upon the first odor learned during mother-infant interactions to apprehend the social environment in the less mature sense of vision, in direct relationship with the ability to reach efficient categorization from the sole visual input.

This work was financially supported by the “Conseil Régional Bourgogne Franche-Comté” (PARI grant), the FEDER (European Funding for Regional Economic Development), the French “Investissements d’Avenir” program, project ISITE-BFC (contract ANR-15-IDEX-0003), and the French National Research Agency (contract ANR-19-CE28-0009).