A few linguists took up Weinreich's challenge and quickly found it to be inadequate. Some of the failures had been anticipated by Weinreich himself, as described above. found an extreme example of divergent incidence in a study of two dialects of
Swiss German, Luzerner and Appenzeller, which evolved independently of each other. Although each dialect had the same set of eleven short vowel phonemes, only one pair ( ~ ) was shown to have a common parent vowel in earlier stages of German. The remaining phonetic similarities between the Luzerner and Appenzeller phoneme sets were fortuitous results of multiple mergers and splits that each dialect underwent separately. , examining and , noted the need for refinements in the original proposal; different researchers did not seem to agree on definitions, disciplines of study, or objects of inquiry. The research and debate concluded that multiple dialects could not be described by a common grammar, at least not under structuralist theory. That is, it would be unfeasible to construct a single grammar for multiple dialects unless their differences were very minor or if it incorporated only a small number of dialects. Related to Weinreich's proposal were efforts in both American dialectology and
generative phonology to construct an "overall system" that represented the underlying representation for all dialects of English. An example of this was the
diaphonemic analysis, made by , that presumably all American varieties could fit. Six of the nine simple vowels in this diasystem are common across most dialects: occurs in
pit, in
pet, in
pat, in
putt, in
put, and in
pot. The other three are found in specific dialects or dialect groups: represents the vowel of
road in
New England varieties; represents a vowel that often appears in stressed syllables in words like
just (when it means 'only'); and represents the vowel of
pot in Southern British and New England dialects. These nine simple vowels can then be combined with any of three offglides () to make 36 possible complex nuclei. This system was popular amongst American linguists (despite criticism, particularly from
Hans Kurath) until demonstrated its inadequacy. The most salient criticism of these broad diasystems was the issue of how
cognitively real they are. That is, whether speakers actually have competence in using or understanding the grammatical nuances of multiple varieties. In certain sociolinguistic circumstances, speakers' linguistic repertoire contains multiple varieties. For example, argues that
Modern Literary Arabic is a diasystem of various interference phenomena occurring when speakers of different
Arabic varieties attempt to speak or read
Literary Arabic. More concretely,
Peter Trudgill put forth what he considered to be a cognitively real diasystem in , a book-length sociolinguistic study of
Norwich. As a critic of Weinreich's original proposal, he approached the concept as a generativist, putting forth a series of rules that could generate any possible output reflected in the diversity and variability of sociologically conditioned linguistic variables. Because most speakers of Norwich could vary their pronunciation of each variable depending on the circumstances in which they are speaking, the diasystem's rules reflected speakers' actual linguistic abilities. Cognitively real diasystems are not limited to humans. For example,
crows are able to distinguish between different calls that prompt others to disperse, assemble, or rescue; these calls show regional variation so that French crows do not understand recorded American calls. Although captive birds show difficulty understanding the calls of birds from nearby regions, those allowed to migrate are able to understand calls from both, suggesting that they have mentally constructed a diasystem that enables them to understand both call systems. Still, these sorts of "idiosyncratic" grammars differ in degree from broader diasystems, which are much less likely to be part of speakers'
linguistic competence. Even Trudgill has argued against their cognitive reality, deeming the concept of a broad diasystem to be a "theoretical dead-end." Although the concept did not withstand scrutiny by research linguists, it nevertheless triggered a surge of academic work that used it in applied linguistics (e.g. for
ESL education materials, composition texts for native speakers, basic linguistics texts, and in the application of linguistics to literary criticism). Diasystemic representations are also possible in dictionaries. For example, the
Macquarie Dictionary reflects the pronunciation of four phonetically distinct sociolects of
Australian English. Because these sociolects are the same phonemically, readers (at least, those from Australia) can interpret the system as representing their own accent. ==See also==