Negative raising

The phenomenon that a negation in the matrix clause of a sentence is interpreted in negating the complement clause.

Example
The negation in the matrix clause (ia) is interpreted in negating the complement clause, which makes (ia) equivalent to (ib):

(i)	a	I don't think he'll come b	I think he won't come

The phenomenon owes its name to the early transformational analysis as an instance of movement (Lakoff 1970): the negation is raised out of its embedded clause to a position in the matrix clause. It is also called neg-raising. Examples of predicates that allow negative raising are believe, want, seem, suppose, likely, ought to, but not know, for instance. Negative raising has later received a pragmatic explanation. The â€˜displacedâ€™ interpretation of the negation results from a strengthening of the unlikely wide interpretation of (ia) to the more likely narrow interpretation that corresponds to (ib). See Horn (1989) for an extensive overview.

Links
Utrecht Lexicon of Linguistics