Can we observe spontaneous smiles in 1-year-olds?

Five infants were observed longitudinally. In over 30 h of observations, seven spontaneous smiles and one spontaneous laugh were found. All smiles were observed in infants between the ages of 10 and 15 months. These data indicate that spontaneous smiles do not disappear at 2 months of age and they still exist at over 15 months. This disproves some emotional expression theories, where spontaneous smiles are considered to be precursor to and replaced by social smiles. Our data suggest that those theories must be revised and provide new perspectives on this field of studies.