How Does Paternal Odor Influence Perception of Fearful and Happy Faces in Infancy?

Social odor plays an important role for various facets of early development, including communication and social processing. Previous research focusing on maternal odor has shown that smelling the mother can influence face processing in general as well as emotion processing more specifically. However, it is unclear to what extent these effects are specific to maternal odor or can also be found for other familiar social odors. To address this question, we investigated the impact of the father's odor on emotional face processing in 7-month-old infants (age at appointment 1: 209 ± 6 days [mean ± SD], range: 199-225 days; age at appointment 2: 217 ± 6 days, range: 206-231 days; gender: 15 girls and 15 boys). We recorded the infant's EEG response to female and male happy and fearful faces while infants were exposed to either their father's odor or the odor of a different infant's father. Analysis of the frontocentral Nc amplitude revealed an enhanced response to fearful compared to happy male faces only when infants smelled their own father but not when they smelled an unfamiliar father. In contrast, emotion processing at the occipital N290 was not affected by the presence of paternal odor, suggesting an impact of social odor on attention allocation rather than structural face processing. Interestingly, all effects were specific to male faces, pointing to a gender-specific impact of social odor. Our findings therefore provide first evidence for an influence of the father's odor on face processing, specifically male faces, in infancy.