Gram - SEAS

3.2 Some background assumptions about change 45
subsystems of a language as "contact-induced," and to other changes as "natural"
(Thomason and Kaufman 1988) or "evolutive" (Paul 1920; Andersen 1973).
3.2.3 Th e question of genetic endowment
Although the model in Figure 3.1 does not force the issue, it was designed
to characterize a grammar of relatively fixed structure at any one period, and
uniformity of input. Such assumptions, as we have seen, are challenged by the
study of grammaticalization (and of sociolinguistics). The model does crucially
claim that there are universal laws of some kind, but, as a model, it does not specify
what kinds of laws they are. Andersen speaks of them as: "the properties of [the
learner's] constitution that completely determine the nature of linguistic structure,
and hence the relation between a grammar and its output" (Andersen 1973: 776).
The key phrase here is "completely determine." The hypothesis is that human
beings are born with a set of constraints on what possible language structures can
be, and ways in which they can vary.
Refinement of this hypothesis has been the major focus of much recent generative
theory. One widely accepted model that has been proposed is that all human beings
are genetically endowed with Universal Grammar (UG) (see, e.g., Chomsky 1981).
This UG is conceived as consisting of two components: unchanging "principles"
that characterize the fundamental structure of language and restrict the class of
attainable grammars, and "parameters" that define the space of possible variation
and are fixed by experience. Ditl"erences between languages across geographic
and social space or across time are conceived as being the result of different settings
of the parameters in the process of language acquisition. Lightfoot (1991)
elaborated on the idea of principles and parameters for change, and argued that
changes from one generation to another are the result of the fact that different
learners select different possibilities from among a restricted set of structures that
are genetically encoded. Specifically, he hypothesized that children contribute to
language learning (and hence to change) at least a "disposition to learn." This
disposition was conceived as a selective one: "an organism experiences the surrounding
environment and selects relevant stimuli according to criteria that are
already present internally" (1991: 2). Such a selective disposition was contrasted
to an "instructive" one, which is essentially flexible and modifiable by outside
stimuli. In this account of motivations for language change, the child is conceived
as an LAD (language acquisition device), a processor of systems, a kind of passive
logic machine with a very rich language-specific genetic endowment.
In recent years the doctrine of innateness (nativism) has come under attack
from several quarters. Sampson (1997) surveys critically the entire range of
evidence that has been put forward for innateness. Tomasello (1999) presents