Syntactic ambiguity
Syntactic ambiguity, also known as structural ambiguity, amphiboly, or amphibology, is characterized by the potential for a sentence to yield multiple interpretations due to its ambiguous syntax. This form of ambiguity is not derived from the varied meanings of individual words but rather from the relationships among words and clauses within a sentence, concealing interpretations beneath the word order. Consequently, a sentence presents as syntactically ambiguous when it permits reasonable derivation of several possible grammatical structures by an observer.
In jurisprudence, the interpretation of syntactically ambiguous phrases in statutory texts or contracts may be done by courts. Occasionally, claims based on highly improbable interpretations of such ambiguities are dismissed as being frivolous litigation and without merit. The term parse forest refers to the collection of all possible syntactic structures, known as parse trees, that can represent the ambiguous sentence's meanings. The task of clarifying which meaning is actually intended from among the possibilities is known as syntactic disambiguation.
Different forms
Globally ambiguous
A globally ambiguous sentence is one that has at least two distinct interpretations and where reading the entire sentence does not resolve the ambiguity. Globally ambiguous sentences exist where no feature of the representation distinguishes the possible distinct interpretations. Global ambiguities are often unnoticed because readers tend to choose the interpretation they understand to be more probable. One example of a global ambiguity is "The woman held the baby in the green blanket." In this example, the baby, incidentally wrapped in the green blanket, is being held by the woman, or the woman is using the green blanket as an instrument to hold the baby, or the woman is wrapped in the green blanket and holding the baby.Locally ambiguous
A locally ambiguous sentence is a sentence that contains an ambiguous phrase but has only one interpretation. The ambiguity in a locally ambiguous sentence briefly stays and is resolved, i.e., disambiguated, by the end of the speech. Sometimes, local ambiguities can result in garden-path sentences, in which a structurally correct sentence is difficult to interpret because one interpretation of the ambiguous region is not the one that makes most sense.Examples
Aristotle writes about an influence of ambiguities on arguments and also about this influence depending on either combination or division of words:In headlines
Newspaper headlines are written in a telegraphic style which often omits the copula, creating syntactic ambiguity. A common form is the garden-path type. The name crash blossoms was proposed for these ambiguous headlines by Danny Bloom in the Testy Copy Editors discussion group in August 2009. He based this on the headline "Violinist linked to JAL crash blossoms" that Mike O'Connell had posted, asking what such a headline could be called. The Columbia Journalism Review regularly reprints such headlines in its "The Lower Case" column, and has collected them in the anthologies "Squad Helps Dog Bite Victim" and "Red Tape Holds Up New Bridge". Language Log also has an extensive archive of crash blossoms, for example "Infant Pulled from Wrecked Car Involved in Short Police Pursuit".Many purported crash blossoms are apocryphal or recycled. One celebrated one from World War I is "French push bottles up German rear"; life imitated art in the Second World War headline "Eighth Army Push Bottles Up Germans".
In humour and advertising
Syntactic or structural ambiguities are frequently found in humour and advertising. One enduring joke using an ambiguous modifier is a quip spoken by Groucho Marx in the 1930 film Animal Crackers: "I shot an elephant in my pajamas. How he got into my pajamas I don't know." Another sentence, which emerged from early 1960s machine translation research, is "Time flies like an arrow; fruit flies like a banana".Significantly enough, structural ambiguities may also be intentionally created when one understands the kinds of syntactic structures that will lead to ambiguity; however, for the respective interpretations to work, they must be compatible with semantic and pragmatic contextual factors.
Syntactic and semantic ambiguity
In syntactic ambiguity, the same sequence of words is interpreted as having different syntactic structures. In contrast, in semantic ambiguity the structure remains the same, but the individual words are interpreted differently. Controlled natural languages are often designed to be unambiguous so that they can be parsed into a logical form.Kantian
employs the term "amphiboly" in a sense of his own, as he has done in the case of other philosophical words. He means it as a confusion of pure understanding with perceived experience, and an attribution to the latter of what belongs only to the former.Models
Competition-based model
Competition-based models hold that differing syntactic analyses rival each other when syntactic ambiguities are resolved. If probability and language constraints offer similar support for each one, especially strong competition occurs. On the other hand, when constraints support one analysis over the other, competition is weak and processing is easy. After van Gompel et al.'s experiments, the reanalysis model has become favoured over competition-based models. Convincing evidence against competition-based models includes the fact that globally ambiguous sentences are easier to process than disambiguated sentences, showing that the analyses do not compete against each other in the former. Plausibility tends to strengthen one analysis and eliminate rivalry. However, the model has not been completely rejected. Some theories claim that competition makes processing difficult, if only briefly.Reanalysis model
According to the reanalysis model, processing is hard once the reader has realised that their analysis is false and he or she must then return and recheck the structure. Most reanalysis models, like the unrestricted race model, work in series, which implies that only one analysis can be supported at a time.Consider the following statements:
- "The dog of the woman that had the parasol was brown."
- "The woman with the dog that had the parasol was brown."
- "The dog with the woman that had the parasol was brown."
Unrestricted race model
The unrestricted race model states that analysis is affected before the introduction of ambiguity and affects which meaning is used before multiple analyses can be introduced. Gompel and Pickering plainly refer to the unrestricted race model as a two-stage reanalysis model. Unlike constraint-based theories, only one analysis can be made at any one time. Thus, reanalysis may sometimes be necessary if information following the first analysis proves it wrong.However, the name "unrestricted race" comes directly from its properties taken from the constraint-based models. As in constraint-based theories, any source of information can support the different analyses of an ambiguous structure; thus the name. In the model, the other possible structures of an ambiguous sentence compete in a race, with the structure that is constructed fastest being used. The more such an analysis is supported, and the stronger the support is, the more likely this one will be made first.
Consider the following statements:
- "The maid of the princess who scratched herself in public was terribly humiliated."
- "The son of the princess who scratched himself in public was terribly humiliated."
- "The son of the princess who scratched herself in public was terribly humiliated."
This is called the underspecification account as readers do not stick to a meaning when not provided with clarifying words. The reader understands someone scratched herself but does not seek to determine whether it was the maid or the princess. This is also known as the "good-enough" approach to understanding language.