The influence of cognitive and conceptual development on language development has been studied most extensively for the acquisition of the lexicon. There is, for example, a large body of research describing the acquisition of object names, and also of temporal adverbials like before and after. Relational terms like verbs, which not only encode semantic content but also establish a grammatical and logical relationship between their arguments, have only recently been explored in greater depth (see Merriman & Tomasello 1995 for a discussion of this negligence). Even less research has been carried out on the relationship between conceptual development and grammatical development. One of the few exceptions is work on the acquisition of temporal morphology. This has been seen as an ideal testing ground because there are clearly a number of cognitive prerequisites for encoding temporally remote events - most saliently, the ability to remember them.

This chapter starts out by discussing two approaches which claim that cognitive or conceptual development are the driving forces behind language development. It will be argued that neither of them can explain grammatical development as we see it in crosslinguistic data on the acquisition of tense and aspect marking. A third approach to the acquisition of grammatical morphemes is thus needed - one that takes into account the different and additional requirements placed on the acquisition process by the semantic and morphosyntactic structure of the specific language being learned.