2.1 Turbidity Theory

Turbidity Theory (Goldrick 2001; van Oostendorp 2008) is an optimality theoretic approach to faithfulness based on containment, which assumes as input-output relationship whereby the former – the input – is contained in the latter – the output.⁷ Crucially, since all the input elements are argued to be always contained in the output, this theory does not allow deletion, which is rather understood as a case of underparsing: the element is not integrated in the prosodic structure, and is thus unpronounced. Technically, this is formalized as a violation of the PARSE constraint (“every phonological element needs to be parsed in the prosodic structure”). Besides, every prosodic position is supposed not to be empty, i.e. it has to be filled with melodic elements. This is forced by the FILL constraint (“syllable positions are filled with segmental material”).

In Turbidity Theory, PARSE and FILL roughly correspond to PRONOUNCE and PROJECT, which point at the two different relations a segment can entertain with a skeletal slot. Basically, this results from splitting the classic autosegmental association relation – if a segment is associated to a skeletal slot, the skeletal slot is also associated to that segment – in two independent relations. The projection relation encodes the (lexically established) association between a phonological element and its skeletal slot. This relation is enforced by the PROJECT constraint (“Assign a violation mark for every projected element that does not correspond to any pronunciation”), and is graphically represented by an arrow pointing from the skeletal slot to the phonological element. The other relation is pronunciation, which ensures the phonetic realization of a given phonological element. This is enforced by the PRONOUNCE constraint (“Assign a violation mark for every pronounced element that does not correspond to any projection”), and is graphically represented by an arrow pointing from the element to the skeletal slot. This is illustrated in (1), where representations are given that show either only the projection relation (1a.), or both the projection and pronunciation relation (1b.).⁸ As established by Turbidity Theory, the phonological element of the latter is faithfully pronounced whereas that of the former does not receive any phonetic interpretation. In other words, a. represents an instance of phonetic emptiness.

Despite the difference in phonetic interpretation, (1a.) and (1b.) are representationally identical, and they thus display the same phonological behavior. This is not the case for representations showing (some degree of) phonological emptiness (e.g. a skeletal slot that projects no phonological element): they are acoustically identical to phonetically empty representations, but they are representationally different and thus display a different phonological behavior. In other words, phonetically empty representations pattern with phonologically empty representations at the level of phonetic interpretation, but with phonologically contentful representations at the level of phonological behavior. As we show below, by allowing for this refinement of the zero morpheme typology, Turbidity Theory help us in better understanding the syncretism patterns characterizing the verbal inflection and adjectival concord of Dutch dialects.

2.2 Verbal inflection

The high degree of variation displayed by the inflectional systems of Dutch dialects proves to be a challenging ground for testing typological generalizations and fine-grained theoretical hypotheses regarding the morphosyntax and its interface with phonology (Ackema & Neeleman 2003; Baerman, Brown & Corbett 2005; Van Oostendorp 2005; 2008; Bennis & MacLean 2006; Aalberse 2007; Aalberse & Don 2009; 2011).

The observed synchronic microvariation results from a diachronic process of deflection that has affected all Germanic language varieties in the course of millennia: while in older stages they displayed a rich inflectional system, the amount of distinctions conveyed by verb-final morphemes has been generally reduced (an extreme case is represented by Afrikaans, whose finite verbs display no inflectional marker at all). This process affected the varieties spoken in the Netherlands and in the northern part of Belgium (Flanders) to a different extent, resulting in a set of inflectional systems ranging from 4 to 1 affixes. As discussed in Bennis & MacLean (2006; henceforth B&M), out of the 253 dialects, more than a half (147 dialects) display (5 different) 3-affixes systems. The dialects spoken along the north-eastern (Groningen and Friesland) and south-eastern (Limburg) borders show 4-affixes systems (19 dialects), unlike the dialects spoken in West- and East-Flanders, Lower Saxony and the River area, where (3 different) 2-affixes systems can be found (86 dialects). Finally, a 1-suffix system can only be found in Beekbergen (Gelderland).⁹ The latter system is assumed to display a zero morpheme.¹⁰ A list of the present-tense inflectional paradigms drawn by B&M¹¹ from the SAND (Barbiers et al. 2005; 2008) is given in Table 1.

Some generalizations that seem to hold for the whole set of dialects have been proposed by B&M, according to whom a) all the 4-affixes systems display a -st PRS.2SG verbal ending and a du/dich 2SG pronoun¹³ and b) the PRS.3SG verbal ending is spelled out by -t. Interestingly, though, there are dialects with a 4-suffixes system that seem to violate a). The variety spoken in Bree, for instance, displays a PRS.2SG -s ending, rather than the expected -st. Similarly, there are dialects, such as the 3-affixes ones spoken in Limburg and the majority (12 out of 17) of the ones spoken in South-East Limburg and in the River area, in which the PRS.3SG affix is -Ø, contradicting b).

As shown by Goeman (1999), many Dutch dialects show an optional process of word final t-deletion, which is particularly productive in the Betuwe region.¹⁴ This process is conditioned by the morphological category of the relevant form, as -t deletes more frequently along the following scale: (regular) SUP < N < PST.PTCP < PRS.3SG < PRS.2SG < PST.¹⁵ Together with the presence of the du/dich 2SG pronoun, which otherwise occurs only in varieties displaying the -st PRS.2SG inflectional ending, the morphological properties of t-deletion suggest that what surfaces in Bree as -s might underlyingly be -st.¹⁶ In other words, the 3-ways distinction in the verbal paradigm of Limburg dialects (PRS.1,3SG ⇒ -Ø, PRS.2SG ⇒ -s, PRS.1,2,3PL ⇒ -en) derives from an underlying 4-way distinction (PRS.1SG ⇒ -Ø, PRS.2SG ⇒ -st, PRS.3SG ⇒ -t, PRS.1,2,3PL ⇒ -en) by means of word-final -t deletion. The -st ⇔ du/dich correlation, thus, can be maintained. Furthermore, note that the varieties displaying an -s PRS.2SG inflectional ending show a “preference for applying t-deletion” (B&M fn 21), and are geographically adjacent to the ones displaying -st.

The properties of t-deletion can also provide some support for the generalization according to which the PRS.3SG marker is -t in the whole Dutch-speaking area (B&M; see also Aalberse & Don 2009). Indeed, if we extend the -t deletion account to the varieties showing only the -Ø ending, such as the Beekbergen and Limburg dialects referred to above, the PRS.3SG ⇒ -t generalization holds without exceptions (notice that the dialect of Beekbergen is spoken in a “strong t-deletion area”; B&M: fn 22). The 3SG ending of these dialects, thus, can be considered a morpheme whose underlying phonological content does not make it to the surface. We conclude, then, that together with the PRS.2SG -st ending, the PRS.3SG ending of the dialects just mentioned represents an instance of a phonetically empty morpheme: there is some morphosyntactic content that is spelled out by a phonological exponent – -t – that receives no phonetic interpretation. This is represented in (2). As shown, the verbal root is underlyingly followed by the expected markers (-st and -t), whose coronal stop, though, lacks the pronunciation relation:

Besides the optionality of t-deletion, the presence of -t in the underlying representation of the relevant endings is betrayed by the activation of progressive voicing assimilation:

As shown in (3), the word-initial fricative of the preposition – /van/ – gets devoiced – [fan] – even if the preceding verbal form – [kom] – does not overtly end in a voiceless consonant. It is interesting to note that, in the 19th century, dialects showing a particularly productive t-deletion process, such as the ones spoken in Betuwe, displayed compensatory lengthening (Goeman 2007: 73):

In the forms given in (4), the length of the word-final consonant of the PRS.3SG forms can be argued to result from a process of progressive place/manner assimilation (similarly to what happens in the forms in (1)): /p-t/ > [pː] and /v-t/ > [fː]. The processes in (3) and (4) are shown in (5), where progressive assimilation of /t/ voicelessness (5a) and compensatory lengthening of /p/ (5b) are represented by the rightward arrow. Letting aside the details of the assimilation process (see Cavirani & van Oostendorp 2017 for a proposal in terms of voicing licensing), note that, despite it being silent (i.e. lack of the pronunciation relation), -t is still part of the phonological representation, and is thus allowed to interact with adjacent segments. In (5a), it ‘suppresses’ /v/ voicing, which hence surfaces as [f]. In (5b), it is still projected by its skeletal slot, which is though spelled-out by the preceding /p/.

(5)	a.	Progressive assimilation
	b.	Compensatory lengthening

Besides the PRS.3SG and PRS.2SG ending, the PRS.1SG inflectional marker also shows interesting properties. Even if there is no trace of the marker itself in the acoustic signal, the phonological behavior of adjacent segments suggests that this inflectional marker is actually equipped with some phonological content. This is supported by the observation that the 1SG inflectional marker can prevent word-final devoicing to apply: whereas word-final devoicing applies systematically throughout the whole Dutch speaking area, if we focus on PRS.1SG forms and their diatopic distribution in the SAND, MAND and GTRP atlases, many exceptions can be found (van Marle & Zonneveld 1980; Zonneveld 1982; Goeman 1999; 2007; van Oostendorp 2005; Cavirani & Van Oostendorp 2017). An example of this exceptional behaviour is represented by the dialect of Tilligte, in which word-final fricatives resist devoicing only when (following long vowels and) occurring root-finally in PRS.1SG verbs.

Apparently, when we look at the forms for ‘faith’ and ‘I believe’, nothing follows the root-final segment. However, whereas the former undergoes devoicing – [ɣeløːf] -, the latter keeps its underlying voicing specification – [ɣeløːv]. Given that devoicing applies regularly in word-final position also in this variety, we are lead to conclude that the fricative of the PRS.1SG form does not really occupy the word-final position, and that it is indeed followed by a phonetically empty PRS.1SG ending that, as in the case of those for PRS.3SG and PRS.2SG, is equipped with morphosyntactic and phonological content. The PRS.1SG marker of the Tilligte dialect would thus be represented as in (7a), where it is compared with a fully pronounced PRS.1SG marker (7b) (see Cavirani & van Oostendorp 2017: 114 for further discussion):

(7)	a.	phonetically empty PRS.1SG
	b.	fully pronounced PRS.1SG

Something similar can be observed in the Stellingwerven dialect (Eastern Friesland), in which, besides to fricatives (preceded by a long vowel), devoicing optionally applies to coronal stops only when they occur in the apparently word-final position of PRS.1SG verbs:

As shown in (8), whereas devoicing obligatorily applies to the word-final coronal segment of nouns – /huːd/ > [huːt ] ‘hat’ -, it is not obligatory in PRS.1SG verbs – /bʌd/ > [bʌt/bʌd] ‘I bet’. We conclude that the PRS.1SG marker in the Stellingwerven dialect is represented as in (7a).¹⁷ PRS.1SG-final stops resist devoicing also in Limburg and South-Brabant dialects. As for the former, Goossens (1977) reports forms such as ix heb ‘I have’, where the bilabial stop keeps its underlying voicing specification (cfr. hebben ‘to have’). As for South-Brabant dialects, see for instance De Vriendt & Goyvaerts (1989), who report the case of the Brussels dialect, where velar stops resist devoicing (when following a nasal segment), as in ik bring ‘I bring’ (cfr. brengen ‘to bring’). More recently, Van Oostendorp (2005) proposes that the root-final velar stop does not belong to the underlying representation, which should actually end with a velar nasal. The stop, thus, would result from a process of epenthesis that applies in word-final position. Crucially, k-epenthesis applies only to singular nouns (/puliŋ/ ‘eel’ > [puliŋk]), and not to PRS.1SG verbs (/ik ziŋ-Ø/ ‘I sing’ > [ik siŋ]), no matter if the velar nasal is not followed by any audible segment in both cases:

The facts in (9) are represented in (10), which shows the contrast between the phonologically empty noun marker and the phonetically empty PRS.1SG marker. As discussed above, only the latter triggers k-epenthesis. We argue that this is due to the fact that the velar nasal is a complex segment, which need to be licensed by a following non-empty nucleus, as the PRS.1SG marker in (10b). Since noun markers are apparently phonologically empty, they cannot license such a complex structure, which needs to be supported by two skeletal positions. This is represented in (10a) as the spreading to and pronunciation by a following skeletal slot of nasal’s velarity, symbolized by k (see Ulfsbjorninn & Larouchi 2016 for similar ideas).

(10)	a.	k-epenthesis
	b.	no k-epenthesis

In the same dialect, voiced coronal stops undergo a process of intervocalic weakening – bieden ‘to offer’ > biejen -, which applies also in 1SG, no matter if no audible vocalic segment follows the stop – ik biej (*ik biet). As shown in (11), the PRS.1SG of ‘to dress’, which shows d-weakening – [klej] -, contrasts with PRS.3SG, which instead shows final devoicing – [klɪt]:

As in the case of the dialects of Stellingwerf and Tilligte, the presence of a vocalic PRS.1SG ending can be thus argued for despite its phonetic absence (as in (7a)).

In Standard Dutch, word-final devoicing applies systematically to all the forms displaying the right structural description, PRS.1SG verbs included (e.g. ik schaad ‘I damage’ > [ɪk sxat]). PRS.1SG verbs, though, display another interesting property. Whereas word-final nasals can be deleted when they occur after /ə/ in prepositions, adjectives, nouns and infinitival endings, they resist deletion when they represent the root-final segment of PRS.1SG forms (Zonneveld 1982; van Hout & van de Velde 2000):

In Standard Dutch, too, the PRS.1SG ending seems to be endowed with some minimal amount of phonological content that prevents root-final segment from occurring in word-final position, in spite of its phonetic emptiness. As a consequence, the nasal cannot be unpronunced (see Cavirani & van Oostendorp 2017 for a formalization of the various degrees of phonological emptiness and the related phonological activity).

2.3 Adjectival concord

When occurring in predicative constructions, Dutch adjectives show no inflectional ending. When used attributively, though, they agree with the noun phrase they modify.

In Standard Dutch, we can identify two inflectional ending, -/ə/ and -Ø, which are selected according to the semantic, syntactic and phonological properties of the relevant noun phrase (Broekhuis 2014). When adjectives modify common gender nouns (i.e. de-words, as in (13a)), they always get the -/ə/ ending, no matter if the noun is singular or plural, definite or indefinite. The (in)definiteness parameter matters, though, if the noun is neuter (i.e. a het-word, as in (13b)), for if indefinite and singular, adjectives take the -Ø ending:

Beside these syntactic restrictions, the selection of the inflectional ending is conditioned by phonological constraints.¹⁸ This is shown in (14), where the syntactic conditions would require -/ə/ to appear on both the adjectives preceding the nouns:

The relevant phonological factors conditioning the apparent failure of agreement on the rightmost adjectives in (14) concern the root-final segment, as the -/ə/ ending is absent when adjectives end in the long vowels /a/, /o/, /i/, or in /ə/ and /ən/:¹⁹

The difference between /a/, /o/ and /i/, and /e/, /y/ and /u/ is arguably due to the prosodic structure of the words containing them: whereas the forms ending in /e/, /y/ and /u/ are stress-final, the ones ending in /a/, /o/ and /i/ are paroxitones. The -/ə/ ending thus only appears if the stem-final vowel is stressed.

Let us stress here that, by allowing for phonological structure not to necessarily reach the phonetic surface, we could think of the spell-out generalization in (16) as exceptionless:

When syntactically licensed, the -/ə/ ending undergoes Vocabulary Insertion. Its pronunciation, though, is phonology’s business: if phonologically licensed, it gets phonetically interpreted, otherwise it stays silent. More precisely, assuming that a) roots universally end in a nucleus (represented by ‘V’; Lowenstamm 1996; 2008) and b) -/ə/ is a floating vowel, we derive the fact that this ending can only be pronounced if licensed by a nuclear position, namely if it can land on the empty nucleus following a root-final consonant (including the glide of forms such as vrij- ‘free’). This is shown in (17), where the failure of /ə/ integration in the phonological structure is represented by the barred line in (17a). This contrast with (17b), where /ə/ docks on the word-final empty V and is therefore integrated in the phonological structure and pronounced.

(17a) thus represents a case of apparently zero morpheme. Abiding by the Vocabulary Insertion rule given in (16), /ə/ enters the derivation, but it fails to be integrated in the structure and gets no phonetic interpretation. Note that this is slightly different from the cases of phonetic emptiness discussed in section 2.2, represented as in (7a). In those cases, the phonological element – /ə/ – is integrated in/part of the phonological structure, i.e. it displays the projection relation. What makes it phonetically empty is the absence of the pronunciation relation. In contrast, in (17a), the schwa has no projection relation (by virtue of it being a floating element), and cannot be pronounced by the word-final empty V, as the latter is already pronouncing the root-final /i/. As a consequence, the schwa keeps on floating. We maintain that a similar analysis holds for adjectives ending in -/ən/ (e.g. opən ‘open’). As discussed above, the root final nasal of adjectives can be left unpronounced (see ex. (12)). We argued that this does not happen to PRS.1SG verbs because the latter are followed by a phonetically empty morpheme (7a). Given what we have just said about adjective concord (e.g. (16)), the question is then how is it possible that there is nasal deletion in this case, while we would expect there to be a schwa that expresses the agreement relation. Put differently, how do the representations of the verbal form and the attributive adjective differ? Building on the hypothesis that the “ideal” Dutch word consist of exactly one trochaic foot (Kooij & van Oostendorp 2003), and on the observation reported above that -/ə/ only appears if the stem-final vowel is stressed, we argue that the floating /ə/ of attributive adjectives fails in being integrated in the word-final empty V slot of /opənV/ because that would create an illicit metrical structure (a dactyl). In other words, a constraint on the metrical structure would make the word-final empty V unavailable to host the floating /ə/, which would keep on floating (as in (17a)). As a consequence, the nasal occurs in word-final position and it can be left unpronounced. This would not happen in PRS.1SG verbs, as in this case /ə/ is not a floating element: as shown in (7a), it comes with its skeletal slot. This means that, when it enters the derivation at Lexical Insertion, /ə/ is already integrated in the phonological representation: it displays the projection relation, which cannot be deleted by the metrical constraint favoring trochaic feet.²⁰ Thus, despite being unpronounced (no pronunciation relation), the PRS.1SG marker prevents /n/ from occurring in word-final position. As a consequence, the latter cannot be left unpronounced.

Moving south to the Dutch-speaking Belgium, the set of adjectival inflectional endings becomes much richer. Taeldeman (1980) identifies four inflectional endings: -/ən/_M, -/ə/_F, -Ø_N and -/ə/_PL. However, even if adjectives agreeing with neuter nouns systematically display the -Ø ending, “synchronically […] there remain indications of a historical -ə” (Taeldeman 1980: 225 fn. 3). For instance, in Flanders and in the northern half of Antwerp, adjectives ending in a long vowel followed by /d/ show no ending when occurring in predicative constructions. As a consequence, the voiced coronal undergoes devoicing: /d/ > [t]. When occurring in attributive constructions, no ending apparently follows the root-final consonant either. However, rather than undergoing devoicing, the coronal consonant turns into a glide:

As in the case of the PRS.1SG ending in Brussels Dutch (see (11)), the root-final coronal behaves as if it were intervocalic, as shown by the fact that the root-final /d/ shows the same behavior in masculine, feminine and plural adjectives, as well as in infinitives and comparatives, whose inflectional endings display an audible vowel:

We take these facts as evidence of -Ø_N actually being a vocalic ending, crucially different from the (absence of any) ending in predicatively used neuter adjectives. This is represented in (20), where the representations are given of ‘dead’ in predicative position (20a) and of ‘dead’ agreeing with N (20b) and F/PL (20c) nouns in attributive position.

Turbidity Theory allows for the formalization of the difference between the forms in (20): at Vocabulary Insertion, when ‘dead’ occurs in predicative position, no segment is inserted, and the word-final nucleus stays phonologically and phonetically empty. As a consequence, the root-final stop gets devoiced. When ‘dead’ occurs in attributive position and agrees with a N noun, a floating /ə/ is inserted and integrated in the word-final empty nucleus. By virtue of it being integrated in the phonological structure, the phonological process of intervocalic weakening can apply to the root-final stop, which turns into a glide. However, since it lacks the pronunciation relation, /ə/ does not make it to the phonetic modules and is thus inaudible. If the attributive ‘dead’ agrees with a F/PL noun, though, /ə/ enjoys both a projection and a pronunciation relation. As a consequence, it triggers intervocalic weakening and is audible.²¹

A similar approach also holds for the Limburg dialects data shown below. In these dialects, feminine, plural and neuter attributive adjectives all lack the schwa ending. Nevertheless, feminine and plural adjectives contrast with neuter adjectives (Van Oostendorp 2005; Hermans 2009). Given the absence of any ending, the contrast needs to be expressed in another way: the tonal profile. As shown in (21), whereas neuter adjectives display Accent 1, feminine, schwa-less adjectives display Accent 2, namely the same tonal profile of masculine adjectives, which crucially end in schwa²²:

Interestingly, the same tonal contrast can be observed in feminine adjectives when occurring in predicative vs attributive position: gríís ‘grey.PRED’ vs gríìs ‘grey.ATTR.F’. According to Hermans (2009: 363), “the forms where the accent alternates […] are morphologically complex [and] have lost an old schwa”. Note that “this morphological bifurcation occurs in all major categories. In adjectives, the empty morpheme presumably marks the feminine gender in attributive position, because in this position all adjective have Accent 1, provided their stem ends in a voiced consonant. In verbs, the empty vowel presumably marks the present tense in strong verbs, because all strong verbs have Accent 1 in the present tense, provided, of course, their stem ends in a voiced consonant and no other overt suffix follows. Finally, in nouns it denotes class membership.”

Limburg dialects, thus, can be argued to resort to a (set of) phonologically empty vocalic morpheme(s), etymologically corresponding to /ə/, and representationally similar to the ones given in (20b).