Polar (yes/no) questions are prototypical cases of Dutch V1-clauses. Although it is usually the V1-order that occurs in written texts, it is possible in speech to mark a polar question with a typical rising intonation; cf. Haan (2002), Haan & Van Heuven (2003), Barbiers (2007:103), Van Heuven & De Clercq (2017) and the references cited there.

Polar V1-questions are usually less marked than polar V2-questions. The primeless examples in (57) are more neutral than the primed examples in that the latter imply a certain expectation on the part of the speaker, or express (lack of) confidence in the truth of the proposition expressed by the clause; cf. Droste (1972). In other words, polar V2-questions have a similar function as the tag-questions in the English translations in the primed examples (which find their Dutch equivalent in the optional particle hè). We will ignore polar V2-clauses in the following.

An important question is whether the clause-initial position in polar V1-clauses is really empty or whether this position is occupied by some phonetically empty polarity operator: [CP OPpolar heeft [TP Peter dat boek gelezen theeft]]? The latter option is advocated in Barbiers (2007/2013) on the basis of the left-dislocation examples in (58). The (a)-examples show that in declarative clauses left dislocation is possible with a resumptive pronoun in the middle field or in the clause-initial position. The (b)-examples, on the other hand, show that the resumptive pronoun cannot occur in the clause-initial position in yes/no questions, which would follow if the first position in polar questions were filled by an empty operator.

The evaluation of this argument is complicated by the fact, indicated by the number sign, that examples such as (58b') are acceptable when pronounced with the intonation contour typical of polar V2-clauses such as (56c), which is somewhat easier to obtain if we add the modal particle toch; Dat boek, dat heeft Peter toch gelezen? This means that we have to assume the two structures in (59): the polar V1-construction in (59a) does not allow movement of the resumptive pronoun into the clause-initial position, since this position is already occupied by the phonetically empty polar operator; the polar V2-construction in (59b) does allow movement.

Since the grammatical and ungrammatical version of (58b') can only be distinguished on the basis of their intonation contour, it would be desirable to provide additional, independent evidence for the hypothesis that polar V1-structures have a phonetically empty operator in the clause-initial position. Such evidence can be provided by the following constructions with the negative polarity phrase ook maar ietsanything. Example (60a) shows that such phrases cannot occur in positive declarative clauses: as their name implies, they typically occur in the context of sentence negation, which is expressed in (60b) by the negation on the subject niemandnobody.

However, negative polarity ook maar-phrases are not only licensed by a negative operator: example (61a) shows that they can also occur in polar questions. This is easily explained if we assume that empty polar operators can also license ook maar-phrases. The fact that the corresponding polar V2-clause in (61b) does not allow an ook maar-phrase is consistent with Barbiers’ claim that such clauses are declarative and thus do not have an empty polar operator. For completeness, note that negation and the polar operator are only two specific cases of a larger set of so-called affective operators that license negative polarity items; cf. Klima (1964), Progovac (1994), Haegeman (1995: §2), and Van der Wouden (1997: Part II) for further discussion.

The discussion above has provided empirical support for the claim that polar V1-clauses have a phonetically empty polar operator in initial position, and thus are only apparent exceptions to the claim that clause-initial positions of main clauses must be filled by some syntactic constituent.