Adults with siblings like children’s faces more than those without

• Examine likeability towards infant & child faces by adults with vs. without siblings.
• Having siblings extend the influence of the baby schema from infants to children.
• Having siblings leads adults to like child faces more than those without siblings.
• Adults show stronger likeability when the face's age is closer to their siblings.
• Innate releasing mechanisms and postnatal experience both affect baby schema.

Humans cross-culturally find infant faces both cute and highly likeable. Their so-called “baby schema” features have clear adaptive value by likely serving as an innate releasing mechanism that elicits caretaking behaviors from adults. However, we do not know whether experience with young children during social development might act to further facilitate this. Here we investigated the potential impact of having siblings on adult likeability judgments of children’s faces. In this study, 73 adult men and women (40 with siblings and 33 without) were shown 148 different face pictures of young children (1 month to 6.5 years) and judged them for likeability. Results showed that both groups found faces of infants (<7 months) as equally likeable. However, for faces more than 7 months of age, whereas the no-sibling group showed a reduced liking for faces with increasing age, the sibling group found faces of all ages as equally likeable. Furthermore, for adults with siblings, the closer in age they were to their siblings, the stronger their likeability was for young children’s faces. Our results are the first to show that having siblings can extend the influence of baby schema to children as well as infants.