This is certainly the most familiar marker of childhood. It is widely known that children are physically short relative to the population at large. This aspect of childhood is often the only basis for a clinician's diagnosis. While many children have IQs with or even above the norm, almost all will manifest knowledge deficits. Anyone who has known a real child has experienced the frustration of trying to discuss any topic that requires some general knowledge.
Children seem to have little knowledge about the world they live in.
Perhaps it is because of this ignorance, but the sad fact that most children have few friends who are not, themselves, children. This last identifying feature is perhaps the most unexpected. Recent years have seen a flurry of theory and speculation from a number of perspectives. Some of the most prominent are reviewed below. Sociological Model Emile Durkind was perhaps the first to speculate about sociological causes of childhood.