1. Babies are born with limited abilities to engage with the world and their behavioral repertoire skews toward the negative and involuntary. It takes weeks before babies first smile unambiguously, marking the beginning of their engagement with the social world.
2. The origins and meaning of smiles remain mysterious despite extensive research. Smiles are often associated with light, warmth, and attention-grabbing qualities. A smile involves the contraction of specific muscles and genuine smiles include eye crinkles.
3. The authenticity of facial expressions, including smiles, is still debated. Facial expressions may not solely reflect internal emotions but can be tools for influencing others. Smiles during activities can be more social responses than direct reflections of happiness.
4. Smiling is a universal human behavior, but there is variability in who smiles and when. Women tend to smile more than men, and smilingness varies across countries based on migration history. Smiling behaviors have also changed across history, becoming more acceptable and associated with play and pleasure.
5. The evolution of smiling and laughing suggests a continuum of integrating signals. Smiles and laughter have origins in primate displays associated with submissiveness and playfulness. Laugh-like vocalizations have been observed in other mammals and birds, indicating a common trait across species.
6. The nature and power of smiles remain intriguing. Smiles can activate reward centers in the brain and elicit positive responses from others, even in babies. Smiles may serve as a means for babies to solicit care and protection when they are most vulnerable.
