In natural settings, human infants tend to prefer infants to older children. Some laboratory-based studies reported that infants also show preference for adults, as much as for the age-mates. We showed that infants looked at infants longer than at children and that they showed banging behaviors more frequently while looking at infants and at adults than while looking at children. Our study suggested different cognitive basis for the infants' preference for infants and for adults: infants' preference for infants might be explained as a combination of the preference for babyish characteristics (same as adults) and the perceptual preference for similar others. On the other hand, the preference for adults might reflect the infants' daily learning through experience. Infants might prefer adults as familiar others.