ABSTRACT
During the first years of their lives, children learning their mother tongue are exposed to a huge number of well-formed sentences, but they are provided with very little "negative" information, i.e., information about what sound sequences are not well-formed (cf. Braine 1971). This fact can help us to gain some insights into the workings of children's language acquisition capacity. In Dell (1981) I discussed some of its implications concerning the way optional phonological rules are acquired. 1 These had to do with the manner in which the language acquisition device (henceforth LAD)
. evaluates alternative hypotheses concerning the structural description of such rules, and their relative ordering in the grammar. In this article I extend my argument to the acquisition of exceptions and I furthermore suggest that under certain assumptions about the way the LAD stores primary linguistic data, some gaps in these data are undetectable for it.
