An investigation of the morphosyntax of number and degree expressions with noun and adjective phrases indicates that the point of variation determining the syntax of number expressions with NPs also determines the syntax of degree expressions with APs. Yet, cross-linguistically, the syntax of number and degree is shown to be independent of any overt morphology. Hence, even where a syntactic parameter can readily be tied to the morphosyntax of functional heads, overt morphology does not exert any necessary effect on the setting of the parameter. A related, acquisitional investigation of the phenomenon of Noun-drop in Spanish is also reported, though the results are less clear-cut.
In one domain, however, an important link is demonstrated between parametric syntax and overt morphology. Languages are shown to permit complex predicate constructions of the type exemplified by the English resultative, if and only if they freely permit the formation of novel Noun-Noun compounds. Moreover, the age when a child acquiring English first produces complex predicates such as verb-particle combinations, is predicted with remarkable accuracy by the age when the child first produces novel Noun-Noun compounds. The complex-predicate/compounding connection is argued to follow from properties of the syntax-semantics interface; a formalization is provided within a neo-Davidsonian framework. The relevant parameter is shown to be independent of any single lexical item. The findings from complex predicates and number/degree expressions, taken together, indicate that points of parametric variation in syntax are not necessarily tied either to overt morphology or to a specific lexical item.