This chapter reports on trends of continuity and divergence within the heritage generations examined and between heritage and homeland varieties. It discusses the degrees of similarities between the varieties in terms of (a) rates of use of innovative forms and (b) conditioning factors in the constraint hierarchy. The three variables examined are voice onset time (VOT, n=8,909), case-marking on nouns and pronouns (CASE, n=9,661), and variable presence of subject pronouns (PRODROP, n=9,190), each in three or more languages. The similarity in rates and conditioning effects across generations for (PRODROP), examined in seven languages, particularly contrasts with findings for this variable in experimental paradigms. Similarly, findings of little simplification or overgeneralization of the case system in three languages stands in contrast to the outcomes of several previous studies. (VOT) shows a drift toward (but not arriving at) English-like values for only some of the languages examined. For each variable, models are presented and interpreted; a table then details which aspects of the analysis contribute to the interpretation of stability and of each type of variation.

This chapter draws cross-linguistic comparisons among the patterns reported in Chapter 5 for three linguistic variables that occur in at least three languages in the project: (VOT), (CASE), and (PRODROP). Conditioning factors, both linguistic and social, are discussed. Collapsing across rate and constraint hierarchy for each variable, we note any indication of change in either. Half the context we examine exhibit stability. Of the eight that indicate difference, half of these can be attributed to English (including both convergence and divergence). With few differences between homeland and heritage speakers to work with, we find few generalizations about what parts of the language, or which languages, change. We do see more change in one morphosyntactic variable, (CASE), than in the phonetic variable (VOT), but less in the other morphosyntactic variable (PRODROP).

This chapter discusses null-subject clauses, those that do not have the subject in the nominative case. Viewing Slavic languages in their totality, there is a range of null subjects from grammatically obligatory to optional (the presence of the subject signifies emphasis or juxtaposition) to pragmatically motivated. If we view the pro-drop feature as a continuum, as suggested by Pešková, from pro-drop in West Slavic and South Slavic to partially pro-drop in East Slavic (more so in Ukrainian, less so in Russian), then we could correlate a construction of the type (i) Uk. Hru-ACC zakinčeno-ppl ‘Game over (finished)’ with the pro-drop languages, and a construction of the type (d) Rus.-Uk. Udarilo-pastNEU gromom-INSTR ‘Hit by lightning (thunder)’ with partially pro-drop languages. In addition, Russian has a propensity to form infinitive constructions that are absent in other languages.

This chapter elaborates on two case studies in structural variation to illustrate how the comparison of closely related grammatical systems fuels research questions on general theoretical issues. Our first case study regards subject clitics in central Romance dialects. Subject clitics have been studied extensively over recent decades, but they still raise several questions concerning the nature of null subject languages. Analogously, there is a huge literature on the selection of perfective auxiliaries – the second case study in our chapter – and, as in the case of subject clitics, lesser-known non-standard dialects display a kaleidoscope of auxiliation options whose rationalization poses fascinating analytical challenges and yields insights into basic issues of linguistic theory. The core question raised by our case studies concerns the modelling of linguistic diversity: do the above phenomena result from a finite set of discrete parameters or emerge from random language-specific options? We argue that the otherwise ‘hyperastronomical’ number of possible grammars is aptly constrained by syntactic factors, although inflexional morphology – which syntax cannot control entirely – may have a role in the realization of specific auxiliary or subject clitic forms in each dialect and for each person.