<P> After increasing until a certain point, overextensions diminish over time as the child receives corrective feedback . This feedback most often comes from parents and teachers, who help the child revise his or her word meaning boundaries . However, parents can also unintentionally prolong the use of overextensions . Parents often respond to overextensions with acceptance, and the use of joint labeling (e.g. referring to both wolves and dogs as puppies) reinforces overextended language . </P> <P> Underextension, which is roughly the opposite of overextension, occurs when a child acquires a word for a particular thing and fails to extend it to other objects in the same category, using the word in a highly restricted and individualistic way . For example, a child may learn the word flower in connection with a rose but fail to extend its meaning to other types of flowers . Although research more commonly addresses the underextension of nouns, this error can also apply to verbs . For example, a child might underextend the verb sit and only use it with reference to the family dog's sitting but no one else's . </P> <P> Underextension is generally thought to be less common, or perhaps just less noticeable, than overextension, but according to Margaret Harris, recent research shows an increasing number of reports of underextension . According to Harris, there are two different kinds of underextension . The first is "context bound", in which a child produces a word only in a limited and specific context . An example is when a child only uses the word duck when hitting a toy duck off the bathtub and chuff - chuff only when pushing a toy train . </P> <P> The second type of early underextension involves restricting a word to a particular referent instead of a particular situation . This kind of underextension is not context - bound but contextually flexible, and suggests that children are using words in a genuinely referential way . Harris mentions examples of this type of underextension from her own research, such as the use of the word clock only to refer to wall clocks and light only to refer to ceiling lights with a shade . </P>

Describe and give examples of underextension and overextension