Syntactic Ambiguity

Syntactic ambiguity occurs when there are many LFs that correspond to the same sentence. This may be the result of scope, movement or binding, and the level at which the ambiguity is localized can involve full sentences or phrases. Here are some examples of purportedly syntactic ambiguities.

3.2.1 Phrasal

A phrase can be ambiguous by failing to exhibit the relevant scopal relations. The classic example:

اقتباس :: superfluous hair remover

can mean the same as ‘hair remover that is superfluous’ or ‘remover of hair that is superfluous’. The ambiguity results from the lack of representation of scope in the English sentence, since it is unclear if the noun ‘hair remover’ is modified by ‘superfluous’ in its specifier or if the adjective ‘superfluous hair’ is the specifier of the noun ‘remover’. In current syntax, the phrase would be associated with two different possible trees which grouped the terms appropriately.
Similarly, a phrase can be ambiguous between an adjunct and an argument:
[list="margin-top: 0.5em; color: rgb(26, 26, 26); font-family: serif; font-size: 16.5px; line-height: 21px; background-color: rgb(255, 255, 255);"]
[*]John floated the boat between the rocks.

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‘between the rocks’ can modify the event of floating, saying where it happened and thus acts as an adjunct. It can also act as an argument of ‘float’, specifying where the resulting location of the boat on account of the floating. It can also act as an adjunct modifying ‘the boat’, helping to specify which boat it is. All of these are readings of (1) and in each case we find ‘between the rocks’ playing very different roles. Assuming these roles are dictated by their point in LF, we get three very different LFs that correspond to (1).
Thematic assignments can be similarly ambiguous at the level of LF with deleted phrases:
[list=2]
[*]The chicken is ready to eat.

[/list]
(2) can mean that the chicken is ready to be fed or to be fed to someone depending on the thematic assignment. In current semantic theory, this is because ‘the chicken’ is assigned agent on one reading and patient on another. Arguably, this is a syntactic phenomenon assuming principles that align thematic role and syntactic position (see Baker 1988, 1997; Williams 1994; and Grimshaw 1990). They result in a clear ambiguity that we may term ‘thematic ambiguity’ for present purposes.
Multiple connectives present similar ambiguities. The following ambiguity, for example, is borne directly out of failure to tell which connective has widest scope:
[list=3]
[*]He got drunk and fired or divorced.

[/list]
We teach our students in propositional logic to disambiguate these with brackets but we are not so lucky when it comes to the orthographic and phonetic groupings in natural language.
An interesting case is the semantics of modals. At least some modal auxiliaries and adverbs seem to allow for distinct senses such as metaphysical, deontic, doxastic and perhaps practical. Consider
[list=4]
[*]John ought to be at home by now.

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(4) can mean that John’s presence at home is, given everything we know, guaranteed. It might mean that, though we have no idea where he is, he is under the obligation to be at home. Similarly:
[list=5]
[*]The coin might come up heads.

[/list]
(5) means that there is an open metaphysical possibility in which the coin comes up heads. It also means that everything we know doesn’t tell us that the coin won’t come up heads. On the latter reading, for example, we can utter (5) truly even if we know that the coin is weighted, but we aren’t sure in which way.
Similarly:
[list=6]
[*]You must eat a piece of cake.

[/list]
(6) can express a moral imperative: you are obliged morally to eat a piece of cake. It can express a practical obligation: given your tastes you’d be remiss if you didn’t eat a piece. Though this would rarely make sense, (6) can suggest a doxastic certainty: everything we know entails that you won’t fail to eat the cake.
The multiplicity of interpretation in these modals is pretty clear. One particularly controversial case involves imperative vs epistemic interpretations of ‘must’ as in ‘He must be here’. However, whether or not it is a lexical or structural ambiguity (or best treated as a case of univocality with indexicality) is a source of some controversy (see Drubig 2001, Other Internet Resources). In the semantics literature, views on which modalities are treated indexically rather than as cases of ambiguity pretty much dominate all contemporary thinking, as we shall see in section 6.3.

3.2.1 Quantifier and Operator Scope

Finally, and of much interest to philosophers and logicians, there are scopal ambiguities involving operators and quantifiers. The classic case is:
[list=7]
[*]Every woman squeezed a man.

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(7) can express
[list=8]
[*][∀x:Wx][∃y:My](x squeezed y)

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(In regimented English: For every womani there is at least one man that shei squeezed.)
Or
[list=9]
[*][∃y:My][∀x:Wx](x squeezed y)

[/list]
(In regimented English: There is at least one mani who is such that every womanj squeezed himi.)
These ambiguities can be very difficult to hear in some cases. For example:
[list=10]
[*]Someone dies in a car accident every 5 minutes.

[/list]
No one is tempted to hear the reading of (10) that involves an unlucky man who dies over and over again in a car accident. Thus, our best theory may determine an ambiguity that is never actually expressed by a sincere utterance of the ambiguous sentence. If we were able to revive people frequently, we would presumably start to consider the currently disprefered reading of (10) more seriously when (10) was uttered.
Operators have scopal interactions with quantifiers as well. The semantics of modal auxiliaries, adverbs, temporal modifiers and tense are the subject of much concern but one thing is clear: they have interactive effects.
Modal and temporal fallacies abound if we aren’t careful about scope:

(P1)

John is a bachelor.

(P2)

[size]All bachelors are necessarily unmarried.[/size]

(C)

[size]Therefore John is necessarily unmarried.[/size]
If we allow ‘necessarily’ to have ‘bachelors’ etc. within its scope, P2 is true but the conclusion is not entailed. If the modal is interpreted narrowly, the conclusion follows but P2 is false and so is the conclusion.
There is a great deal of controversy over how scope is to be handled. Orthodoxy suggests movement of quantifiers at LF where quantifier scope is made explicit and unambiguous. May (1985) is often cited as the canonical source for this—but it is worth nothing that in that work May treats the LF as underdetermining semantic scopal relations. The situation is less clear with temporal and modal (and other) operators: many semantic theories treat tense and temporal adverbs as quantifiers, while some treat modal expression in this manner. Other treat them as the operators or adverbs they appear to be. One respectable semantic tradition sees (P2) as ambiguous, for example, between:
[list=11]
[*][∀w][∀x:Bachelor(w,x)](Unmarried(x,w))

[/list]
(In regimented English: Every world is such that every bachelor at that world is unmarried at that world.)
And
[list=12]
[*][∀x:Bachelor(w,x)][∀w′](Unmarried (x,w′))

[/list]
(In regimented English: Every bachelor at a world is such that at every world he is a bachelor.)
On the first reading, the world-quantifier takes wide scope. On the second, the bachelor-quantifier takes wide scope and the world variable is unbound. On the operator treatment, we dispose of quantification over worlds and let the predicates be interpreted relative to the operators, perhaps as a matter of movement, perhaps by other semantic means.
Negation has similarly been argued to present interesting scope ambiguities (see Russell (1905) for an early example of a philosophical use of this type of ambiguity). The following, according to Russell, is ambiguous:
[list=13]
[*]The present king of France is not bald.

[/list]
As is:
[list=14]
[*]All that glitters is not gold.

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(13) and (14) seem to be ambiguous between a negation that scopes over the sentence as a whole and one that scopes under the determiner phrase and over the predicate (though see Strawson (1950) ).
Long story short, of great interest to philosophers are these sorts of scope worries as many an argument has been accused of looking convincing because of a scope ambiguity (the causal argument for God’s existence, the ontological argument). The development of logics capable of handling multiple quantification was an achievement in part because they could sort out just this sort of linguistic pitfall.
One final note: even in the domain of scopal ambiguities, there are controversies about whether to treat these apparent ambiguities as ambiguities. Pietroski and Hornstein (2002) argue that many of these cases aren’t ambiguities at all and prefer a pragmatic explanation of the multiple readings.

3.2.2 Pronouns

Bound and unbound readings of pronouns give rise to similar problems, though whether this is a semantic, syntactic or pragmatic ambiguity has been the source of heated debate. If I tell you ‘everyone loves his mother’, the sentence may be interpreted with ‘his’ being co-indexed with ‘everyone’ and yielding different mothers (potentially) for different values of ‘everyone’ or it could be interpreted deictically saying that everyone loves that [appropriate demonstration] guy’s mother. Static semantics usually treats the distinction between bound and free pronouns as a fundamental ambiguity; dynamic semantics relegates the distinction to an ambiguity in variable choice (see Heim 1982, 1983, and Kamp 1981).
The phenomenon is subject to syntactic constraints. We have a good idea of the conditions under which we can fail to get bound readings, as characterized by binding theory. Thus, we know that binding is impossible in cross-over cases and cases where pronouns are ‘too close’ to their binder (known more formally as principle B of binding theory):
[list=15]
[*]?His1 mother loves John1.

[*]*He1 loves John1.

[*]*John1 loves him1.

[/list]
However, the impossibility of these readings simply puts constraints on sentence interpretation. It doesn’t resolve the ambiguity in sentences where violations of binding theory do not occur. We thus seem to have ambiguity that depends on certain structural features of the sentence. This claim, however, is somewhat controversial.

» Syntactic Categories and Semantic Types
» Ambiguity
» Pragmatic Ambiguity
» Detecting Ambiguity
» . What (Linguistic) Ambiguity Isn’t

Syntactic Ambiguity

3.2.1 Phrasal

3.2.1 Quantifier and Operator Scope

3.2.2 Pronouns

Syntactic Ambiguity :: تعاليق

Syntactic Ambiguity

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