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.Billot, Sylvie, and Bernard Lang. "The structure of shared forests in ambiguous parsing." Proceedings of the 27th annual meeting on Association for Computational Linguistics. Association for Computational Linguistics, 1989.Kurohashi, Sadao, and Makoto Nagao. "Building a Japanese parsed corpus while improving the parsing system." Proceedings of The 1st International Conference on Language Resources & Evaluation. 1998. The task of clarifying which meaning is actually intended from among the possibilities is known as syntactic disambiguation.MacDonald, Maryellen C., Neal J. Pearlmutter, and Mark S. Seidenberg. "The lexical nature of syntactic ambiguity resolution ." Psychological review 101.4 (1994): 676.
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 (e.g., word order and/or grammatical inflection) 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 sentence. 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 "The duke yet lives that Henry shall depose." — Henry VI (1.4.30), by William Shakespeare Henry will depose the duke. The duke will depose Henry. Amphiboly occurs frequently in poetry, sometimes owing to the alteration of the natural order of words for metrical reasons.
"" — Edward II by Christopher Marlowe Isabella of France and Roger Mortimer, 1st Earl of March supposedly plotted to murder Edward II of England in such a way as not to draw blame on themselves, sending this order in Latin which changes meaning depending on where the comma is placed. Do not be afraid to kill Edward; it is good. (either killing Edward or not being afraid to kill him is good) Do not kill Edward; it is good to fear. (The act of killing Edward is good to fear)
"I'm glad I'm a man, and so is Lola" from the song "Lola" by the Kinks (written by Ray Davies) Lola and I are both glad I'm a man. I'm glad I'm a man, and Lola is also a man. I'm glad I'm a man, and Lola is also glad to be a man.
"John saw the man on the mountain with a telescope." John, using a telescope, saw a man on a mountain. John saw a man on a mountain which had a telescope on it. John saw a man on a mountain who had a telescope. John, on a mountain and using a telescope, saw a man. John, on a mountain, saw a man who had a telescope.
"The word of the Lord came to Zechariah, son of Berekiah, son of Iddo, the prophet." – Zechariah 1:7 (King James Version) ... the prophet Zechariah, who was the son of Berekiah, who was the son of Iddo ... Zechariah, who was the son of the prophet Berekiah, who was the son of Iddo ... Zechariah, who was the son of Berekiah, who was the son of the prophet Iddo ... the prophet Zechariah, who was the son of Berekiah and Iddo ... Zechariah, who was the son of Berekiah and Iddo, the prophet
Lesbian Vampire Killers, the title of a 2009 comedy-horror film Lesbians who kill vampires. Killers of lesbian vampires. Lesbian vampires that are killers.
"The Purple People Eater", a 1958 novelty song by Sheb Wooley A purple creature that eats people. A creature that eats purple people. (This interpretation is confirmed in the lyrics, although whether the creature itself is also purple is never made clear.)
"British Left Waffles on Falkland Islands", a 1982 headline in The Guardianheadline, The Guardian, April 28, 1982, as quoted by Gloria Cooper, "Mailbag", Barron's, February 19, 2001 The left-leaning British political party is indecisive about Falkland Island policy. British people are responsible for leaving waffles (the breakfast item) on the Falkland Islands.
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 often written in headlinese, a compressed register that frequently omits function words such as the copula. This omission can create syntactic ambiguity, often in the form of garden-path sentences, in which an initial interpretation turns out to be incorrect. The term crash blossom was coined by Dan Bloom in the Testy Copy Editors discussion group to describe such headlines. The name comes from the headline "Violinist linked to JAL crash blossoms" which initially appears to describe a Japan Air Lines plane crash involving "blossoms", rather than a violinist whose career blossomed after being linked to the crash.Ben Zimmer, "On Language: Crash Blossoms", New York Times Magazine, January 27, 2010 online text
The Columbia Journalism Review has reprinted crash blossom headlines in the column "The Lower Case" and has published anthologies of them called "Squad Helps Dog Bite Victim"Gloria Cooper, ed., Squad Helps Dog Bite Victim, and other flubs from the nation's press, Dolphin Books, 1980, and "Red Tape Holds Up New Bridge".Gloria Cooper, Red tape holds up new bridge, and more flubs from the nation's press, Perigee Books, 1987. The Language Log blog has an extensive archive of crash blossoms, including:
"Woman burned as a baby tracks down nurse who cared for her" – Chicago Tribune, 2015 "Knife crime: St John Ambulance to teach teens to help stab victims" – BBC News, 2021 "Driving waste and recycling innovation for the world" – ad for University of New South Wales, 2019 "German factory orders slide unexpectedly" – The Guardian, 2015
Many purported crash blossoms are apocryphal or recycled.1997 Headlines at Snopes.com. One celebrated example from World War I is "French push bottles up German rear", which was echoed in the Second World War headline "Eighth Army Push Bottles Up Germans".Fritz Spiegl, What The Papers Didn't Mean to Say Scouse Press, Liverpool, 1965
In humour and advertising 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.Layman E. Allen "Some Uses of Symbolic Logic in Law Practice" 1962J M.U.L.L. 119, at 120;L.E. Allen & M.E. Caldwell "Modern Logic and Judicial Decision Making: A Sketch of One View" in H.W. Baade (ed.) "Jurimetrics" Basic Books Inc., New York, USA, 1963, 213, at 228 Controlled natural languages are often designed to be unambiguous so that they can be parsed into a logical form.
Kantian Immanuel Kant 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.adapted from Garden, Francis A Dictionary of English Philosophical Terms (1878)
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 (2005), 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 (clearer) 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 (with respect to the already adopted syntactic structure) and they 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."
Research supports the reanalysis model as the most likely reason for why interpreting these ambiguous sentences is hard. Results of many experiments tracking the eye-movements of subjects have demonstrated that it is just as hard to process a persistently ambiguous sentence (1) as an unambiguous sentence (2 and 3) because information before the ambiguity only weakly leans towards each possible syntax.
Unrestricted race model
The unrestricted race model states that analysis is affected before the introduction of ambiguity and affects which meaning is used (based on probability) 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: