Abstract This paper decribes cyclical changes in negative and wh-constructions as a change from Spec(ifier) to Head. It accounts for this change through an economy principle that says 'if possible, be a head'. The changes examined all show a tendency towards heads and head-checking but execute this in slightly different ways. In addition, innovations introduce new specifiers, and prescriptive rules retain them, counteracting the effects of economy. Changes from Head to Head and from Spec to Spec also occur. These proceed typically towards positions higher in the tree and can be explained via a 'merge over move' economy principle. The change involving heads I'll look at is the change of to from preposition to complementizer, and the changes involving specifiers involve French negatives and English relatives. Thus, certain instances of grammaticalization can be accounted for in structural terms.