Dentition mammals the infants have a set of teeth that fall out and are replaced by adult teeth. These are called deciduous teeth, primary teeth, baby teeth or milk teeth. Animals that have two sets of teeth, one followed by the other, are said to be diphyodont. Normally the dental formula for milk teeth is the same as for adult teeth except that the molars are missing. Because mammal teeth are specialised for different functions, many mammal groups have lost teeth not needed in their adaptation. Tooth form has also undergone evolutionary modification as a result of natural selection for specialised
Language acquisition by deaf children but do not use sign language have better communication outcomes and social well-being than Deaf children who use sign language. The general stages of language acquisition are the same whether the language is spoken or signed. There are certain unique features of sign language acquisition due to the visual/manual modality and these differences can help to distinguish between universal aspects of language acquisition and aspects that may be affected by early experience. The very earliest linguistic tasks facing newborns are perceptual. Babies need to determine what basic linguistic elements are used in their native language to create words (their phonetic