the 1960s. Creoles fro mall over the world are often found to have gra m matical devices not traceable to any of the
parent languages of the pidgin.^47 Thus, Bickerton's argument goes, Creole grammar must have come from the
children's expectations of “what a language has to look like”—i.e. Universal Grammar—and they build these
expectations into their linguistic output. The children's parents, on the other hand, do not learn the Creole; they
continue to speak the pidgin, because they are past the critical period. (See also the papers in DeGraff 1999.)
The case of creolization differs fro mho me sign in so me i mportant ways. First, Creoles are full languages, with full
grammar. By contrast, home sign systems are quite rudimentary, comparable with the language competence of two-
and-a-half- to three-year-olds. One possible reason for this is that Creoles have some raw material to work with: the
antecedent pidgin. Another possible reason is that there is a sizeable community of children“working on the creole
together”; by contrast, home sign children are working in isolation, in the sense that they are teaching their parents
rather than the other way around. This is a point where one might be inclined to look for an“emergent system
dynamics”effect in language learning, of the sort alluded to in section 4.5: the syste mcannot be developed by an
individual alone, without a surrounding community that is co-developing it.
- Thefinal case, documented by Kegl et al. (1999), combines elements of the previous two. In the 1980s a
school for the deaf was instituted in Nicaragua, bringing together a community of individuals whose only
communication system up that pointwas through home signs. Withina fewyears, thiscommunitywas found
to be speaking a brand new sign language of altogether expectable sort, without any formal instruction in
sign.Over theensuingtenyears, thelanguage has developedfurther elaborationsinitsgrammatical structure;
these are used by recent learners but not by earlier learners (evidently because the latter have passed beyond
thecriticalperiod).Besidesofferingthewonderofa wholelanguagecoming outofnowhere,NicaraguanSign
Language sheds some light on questions about creole. Evidently a community is necessary for language
creation, but a common stock of pre-existing raw material is not.
Elman et al. (1996), in reference to the home sign, creolization, Nicaraguan Sign Language material, respond as
follows:
100 PSYCHOLOGICAL AND BIOLOGICAL FOUNDATIONS
(^47) This point has beencontroversial.However, Roberts (1998) , through a painstaking examinationofwritten documents from the periodof emergence of HawaiianCreole (c
. 1900–20), argues in detail that none of the sources fro mwhich the Creole putatively borrowed gra m matical features in fact can have served the purpose.