Diphthongisation of variable vowels in the language of middle and younger generation of Eastern Aukštaitians of Vilnius.

Separate geographical ranges of diphthongisation of the Baltic sounds *ā, *ē, i.e. their turning into uɔ·/uo, iẹ·/ie, are scattered all over the area of the Lithuanian language, e.g. they are localised in the area of Western Zemaitian, Southern Aukštaitian, Ciskädi (Latvia). The aforementioned vowels are also diphthongised in the eastern and south-eastern local dialects of Eastern Aukštaitian of Vilnius. This phenomenon is quite extensively described on the basis of the traditional-static picture of the Eastern Aukštaitian subdialect of Vilnius (corresponding to the so-called NORM criterion); however, until now it has not been studied from the dynamic point of view, i.e. whether diphthongisation survives in the semi-dialectal or non-dialectal language of the representatives of the subdialect, the language of different generations, etc. The material for the investigation was collected from 21 locations of the "Atlas of the Lithuanian Language", which are situated in Švenčionys and Ignalina districts. During the investigation diphthongisation realised in the speech of the younger (under 30 years of age) and middle (between the ages of 31 and 50 years) generation is compared with the data obtained when studying the speech of the older (from 51 years of age) generation. It was established in the course of the study that from the geographical point of view the prevalence of diphthongisation is gradually decreasing. Also, the correlation between diphthongisation and the age of the informants was established: diphthongisation in the speech of the informants of the middle and especially younger generation is smaller than that in the speech of the representatives of the older generation. This enables us to rule out the possibility of diphthongisation as a result of Baltic-Slavic bilingualism: diphthongisation was determined by the internal development of the system of vocalism of the speakers of the subdialect of Vilnius. Diphthongisation can be attributed to distinctive dialectal features, which are avoided when speaking in a non-dialectal way. The investigation also showed that the maintenance of the Baltic vowels *ā, *ē, in an unstressed position is to be attributed to the fading features of the subdialect, which enable the informant who speaks in semi-dialect or non-dialect to be identified as a representative of the subdialect of Vilnius