note that controlling for dialect is largely unimportant for eliciting identifications when vowels are placed between consonants, possibly because the /CVC/ structure often forms lexical items that can aid in identification; identifying vowels in isolation, which don't often carry such lexical information, must be matched to the listener's set of vowel prototypes with less deviation than in consonantal contexts. In the first chapter of , Peter Trudgill makes the case that these semantic contexts form the basis of intelligibility across varieties and that the process is irregular and ad hoc rather than the result of any sort of rule-governed passive polylectal competence. argues that a child's language acquisition process includes developing the ability to accommodate for the different varieties they are exposed to (including ones they would not actually employ) and the social significance of their use. point out that there may be critical periods for this similar to those for language learning. This competence in multiple varieties is arguably the primary vehicle of linguistic change. John Wells argues that going past the common core creates difficulties that add greater complexity and falsely assume a shared underlying form in all accents: "Only by making the diaphonemic representation a rather remote, underlying form, linked to actual surface representations in given accents by a long chain of rules–only in this way could we resolve the obvious difficulties of the taxonomic diaphoneme." Wells gives the example of straight, late and wait, which rhyme in most English varieties but, because some dialects make phonemic contrasts with the vowels of these words (specifically, in parts of the north of England), a panlectal transcription would have to encode this contrast despite it being absent for most speakers, making such a system "a linguist's construct" and not part of the grammar present in any native speaker's mind (which is what adherents of such a system attempt to achieve). argues that such constructs are appropriate but only when they are removed before the final formulation of grammatical analysis. Wells puts even more weight on the phonotactic difference between rhotic and non-rhotic accents—the former have an underlying in words like derby and star while the latter, arguably, do not—and to the unstressed vowel of happy, which aligns phonetically with the vowel of in some varieties and that of in others. Hans Kurath, particularly prominent in comparative analysis of British and American regional features, makes the case that the systematic