How do underextension and overextension differ?

How do underextension and overextension differ?

• A. Overextension applies to too many referents
• B. Underextension restricts a word’s usage to a narrow referent; overextension applies a word to too many referents.
• C. Underextension broadens a word's meaning
• D. They both refer to syntax development

Answer: (B)

The main idea here is how toddlers map words to meanings can be either too narrow or too broad. Underextension happens when a child uses a word for a very limited set of items—often just the one example they know. For instance, only using the word “dog” for their family pet and not recognizing other dogs as dogs. Overextension is the opposite: a word is applied to many different things, like calling all four‑legged animals “dog” or every vehicle a “car.” These patterns show the same underlying process—building categories as words are learned—but one narrows the reference, while the other broadens it. That contrast—underextension restricting usage to a narrow referent and overextension applying a word to too many referents—is the best description.

The main idea here is how toddlers map words to meanings can be either too narrow or too broad. Underextension happens when a child uses a word for a very limited set of items—often just the one example they know. For instance, only using the word “dog” for their family pet and not recognizing other dogs as dogs. Overextension is the opposite: a word is applied to many different things, like calling all four‑legged animals “dog” or every vehicle a “car.” These patterns show the same underlying process—building categories as words are learned—but one narrows the reference, while the other broadens it. That contrast—underextension restricting usage to a narrow referent and overextension applying a word to too many referents—is the best description.