Masked or not, I smile to you: Exploring full-term and preterm infants' social smiles to adults wearing a protective facemask.

The early emergence of social smiles is an important milestone of infants' socio-emotional development. Our aim was to assess how the use of protective facemasks by adults affects the display of social smiles in preterm (PT) and full-term (FT) infants at 3 months (corrected age for prematurity). We enrolled 30 FT and 30 PT infants (gestational age ≤ 32 weeks). Infants' social smiles displays were assessed at 2-3-month-age (corrected) across a three-episode (masked mother; unmasked mother; masked adult female stranger) videotaped interactive task. During each episode, the adult was instructed to maintain specific facial expressions (happy-smiling, sad-frowning, neutral-unresponsive) for 15 second windows and then instructed to interact spontaneously for 45 s (of which the first 15 s were coded). FT and PT infants did not differ in the display of social smiles. In both groups, social smiles were mostly exhibited in response to happy/smiling and spontaneously interacting partners. Overall, no effect of wearing a protective facemask emerged. The use of protective facemasks did not result in a lower display of social smiles. The findings suggest that FT and PT might be equally sensitive to their adult interactive partners in terms of social smiles displays at 2-3-month-age.