In linguistics, a yes–no question, formally known as a polar question or a general question  is a question whose expected answer is either "yes" or "no". Formally, they present an exclusive disjunction, a pair of alternatives of which only one is acceptable. In English, such questions can be formed in both positive and negative forms (e.g. "Will you be here tomorrow?" and "Won't you be here tomorrow?").
Yes–no questions are in contrast with non-polar wh-questions, with the five Ws, which do not necessarily present a range of alternative answers, or necessarily restrict that range to two alternatives. (Questions beginning with "which", for example, often presuppose a set of several alternatives, from which one is to be drawn.)
How such questions are posed
Yes–no questions are formed in various ways in various languages. In English, a special word order (verb–subject–object) is used to form yes–no questions. In the Greenlandic language, yes–no questions are formed with a special verb morphology. In Latin, yes–no questions are indicated by the addition of a special grammatical particle or an enclitic. In some languages, such as in Modern Greek, Portuguese, and the Jakaltek language, the only way to distinguish a yes–no question from a simple declarative statement is the rising question intonation used when saying the question. (Such questions are labelled declarative questions and are also available as an option in those languages that have other ways of asking yes–no questions.)
In Latin, the enclitic particle -ne (sometimes just "-n" in Old Latin) can be added to the emphatic word to turn a declarative statement into a yes–no question. It usually forms a neutral yes–no question, implying neither answer (except where the context makes it clear what the answer must be). For example:
- Tu id veritus es.
- "You feared that."
- Tu-nē id veritus es?
- "Did you fear that?"
In Esperanto, the word ĉu added to the beginning of a statement makes it a polar question.
- Vi estas blua.
- "You are blue."
- Ĉu vi estas blua?
- "Are you blue?"
Yes–no questions are also formed in Latin with nonne to imply that the interrogator thinks the answer to be the affirmative and with num to imply that the interrogator thinks the answer to be the negative. For examples:
num negāre audēs?
("You dare not deny, do you?")
Mithridātēs nōnne ad Cn. Pompeium lēgātum mīsit?
("Didn't Mithridates send an ambassador to Gneaus Pompey?")
In many Germanic languages, yes-no questions are formed using subject inversion. In Dutch:
- Ik ben een jongen
- "I am a boy"
- Ben ik een jongen?
- "Am I a boy?"
There is an ambiguity in English as to whether certain questions actually are yes–no questions in the first place. Syntactically identical questions can be semantically different. It can be seen by considering the following ambiguous example:
- Did John play chess or checkers?
The question could be a yes–no question or could be a choice question (also called alternative question). It could be asking the yes–no question of whether John played either of the games, to which the answer is yes or no; or it could be asking the choice question (which does not have a yes–no response) of which of the two games John played (with the presupposition that he played one or the other), to which the answer is the name of the game. Another such ambiguous question is "Would you like an apple or an orange?" to which the responses can be "An apple", "An orange", "Yes", and "No", depending from whether the question is seen as a choice question or a yes–no question. (The "yes." answer involves a further ambiguity, discussed below.)
A related ambiguity is questions with the form of yes–no questions but intended not to be. They are a class of questions that encompass indirect speech acts. The question "Can you reach the mustard?" is an example. In form and semantics, it is a straightforward yes–no question, which can be answered either "Yes, I can" or "No, I cannot". There is, however, an indirect speech act (which Clark calls an elective construal) that can optionally be inferred from the question, namely "please pass the mustard". Such indirect speech acts flout Grice's maxim of manner. The inference on the part of the listener is optional, one that can legitimately remain untaken.
Clark describes one study where a researcher telephoned fifty restaurants around Palo Alto, California, asking without embellishment the question "Do you accept credit cards?" The three forms of reply given were:
- "Yes, we do." – The respondent assumed a straightforward yes–no question, taking the form of the question at face value.
- "Yes, we accept Mastercard and Visa." – The respondent assumed a straightforward yes–no question but provided additional information, either as explanation ("The answer is 'yes' because we accept these two.") or as anticipation or inference of a further request as to what credit cards are accepted.
- "We accept Mastercard and Visa." – The respondent not only took the question to be the indirect speech act but also assumed that the question was not a yes–no question, despite its form and so did not provide a yes–no answer at all.
Another part of the same study was the question "Do you have a price on a fifth of Jim Beam?" Out of 100 merchants, 40 answered "Yes". A non-response bias forced researchers to disregard the survey question asking tobacconists "Do you have Prince Albert?" as although the researchers' intent was to observe whether the merchants specified that they offered the tobacco brand as packaged in a can and/or a pouch, the merchants frequently hung up the phone, presumably because they believed themselves to be the victims of a popular prank call.
According to Grimes, the answer "yes" asserts a positive answer and the answer "no" asserts a negative answer, irrespective of the form of the question. However, simple "yes" or "no" word sentence answers to yes–no questions can be ambiguous in English. For example, a "yes" response to the question "You don't beat your wife?" could mean either "yes, I don't beat my wife" or "yes, I do beat my wife" depending from whether the respondent is replying with the truth-value of the situation or to the polarity used in the question. The ambiguity does not exist in languages that employ echo answers. In the Welsh language, for example, the response "ydw" ("I am") has no such ambiguity when it is used to reply to a question.
Other languages also do not follow the custom, given by Grimes, with respect to the answers "yes" and "no". In New Guinea Pidgin, Polish and Huichol, the answer given has the logical polarity implied by the form of the question. "Bai Renjinal i ranewe, o nogat?", a positive form of a question translated as "Will Reginald escape?", is answered "yes" (agreement, he will escape) or "nogat" (disagreement, he will not escape). Phrased negatively, however, as "Bai Rejinal i no ranewe, o nogat?" ("Won't Reginald escape?") the senses of the answers take the opposite polarity to English, following instead the polarity of the question. An answer of "yes" is agreement that he will not escape, and a response of "nogayt" is disagreement, a statement that he will escape.
A further ambiguity with yes–no questions, in addition to that of polarity, is the ambiguity of whether an exclusive or inclusive disjunction is meant by the word "or", as it can represent either. Conventionally, in English yes–no questions the "or" represents an exclusive disjunction. However, as with the "Would you like an apple or an orange?" question mentioned earlier, to which one possible answer, as a yes–no question, is "yes.", yes–no questions can also be taken to be inclusive disjunctions. The informativeness of the "or" in the question is low, especially if the second alternative in the question is "something" or "things". The "exclusive" and "inclusive" can be determined often in spoken language (the speaker will often lower their pitch at the end of an "exclusive" question, as opposed to raising it at the end of an "inclusive" question), but it is a frequent source of humour for computer scientists and others familiar with Boolean logic, who will give responses such as "yes" to questions such as "Would you like chicken or roast beef for dinner?". However, the ambiguity is not confined to humour. The apple-or-orange question may be legitimately asking whether either is wanted, for example, and "Would you like an apple or something?" is indeed expecting either "yes" or "no" as a proper answer rather than the answer "Something" that an exclusive disjunction would be requesting.
This ambiguity does not exist only in English. It exists in West Greenlandic Kalaallisut, for example. The question "Maniitsu-mi Nuum-mi=luunniit najugaqar-pa" ("Does he live in Maniitsoq or Nuuk?") is ambiguous as to whether exclusive or inclusive disjunction is meant. Commonly, this is clarified either by intonation (if the question is spoken) or the inclusion of an explicit question-word such as "sumi" ("where").
Yes–no questions are believed to carry some suggestibility load. For instance, in response to yes-no questions, children tend to display a compliance tendency: they comply with the structure of the question, negative or positive, by responding in the same way.
For example, if preschoolers are asked, "Is this book big?", they will tend to respond "Yes, it is". But if they are asked, "Is this book not big?" they are more likely to say, "No, it is not".
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