PERSPECTIVE The logic of indirect speech Steven Pinker*†, Martin A. Nowak‡, and James J. Lee* *Department of Psychology, and ‡Program for Evolutionary Dynamics, Departments of Mathematics and Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138 Edited by Jeremy Nathans, Johns Hopkins University School of Medicine, Baltimore, MD, and approved December 11, 2007 (received for review July 31, 2007) When people speak, they often insinuate their intent indirectly rather than stating it as a bald proposition. Examples include sexual come-ons, veiled threats, polite requests, and concealed bribes. We propose a three-part theory of indirect speech, based on the idea that human communication involves a mixture of cooperation and conflict. First, indirect requests allow for plausible deniability, in which a cooperative listener can accept the request, but an uncooperative one cannot react adversarially to it. This intuition is sup- ported by a game-theoretic model that predicts the costs and benefits to a speaker of direct and indirect requests. Second, language has two functions: to convey information and to negotiate the type of relationship holding between speaker and hearer (in particu- lar, dominance, communality, or reciprocity). The emotional costs of a mismatch in the assumed relationship type can create a need for plausible deniability and, thereby, select for indirectness even when there are no tangible costs. Third, people perceive language as a digital medium, which allows a sentence to generate common knowledge, to propagate a message with high fidelity, and to serve as a reference point in coordination games. This feature makes an indirect request qualitatively different from a direct one even when the speaker and listener can infer each other’s intentions with high confidence. eople often don’t blurt out what cesses by which speakers veil their human communication. In cases of pure they mean in so many words but requests and hearers recover them have cooperation, one expects maximally effi- veil their intentions in innuendo, been well documented (1–3). However, cient conspiratorial whispers; in cases of euphemism, or doublespeak. Here the reason people engage in these maneu- pure conflict, one expects a shouting P vers in the first place (as opposed to say- are some familiar examples: match (8). The complex, coded communi- ing what they mean clearly and succinctly) que´s that characterize human language Y Would you like to come up and see is still largely unexplained. In this Perspec- bespeak a mixture of cooperation and my etchings? [a sexual come-on] tive, we apply ideas from the analysis of Y If you could pass the guacamole, that conflict. This conclusion is reinforced by signaling in evolutionary biology and from considering that most of the practical ap- would be awesome. [a polite request] evolutionary game theory to illuminate Y Nice store you got there. Would be a plications of indirect speech (diplomacy, possible advantages of indirect speech (4). extortion, bribery, and sexual harassment) real shame if something happened to Existing theories of indirect speech are take place in arenas of conflict. it. [a threat] based on the premise that human conver- Indirect speech takes many forms, in- Y We’re counting on you to show lead- sation is an exercise in pure cooperation, cluding gestures of sympathy and defer- ership in our Campaign for the Fu- in which conversational partners work ture. [a solicitation for a donation] together toward a common goal—the effi- ence (termed ‘‘positive politeness’’ and Y Gee, officer, is there some way we cient exchange of information, in the in- ‘‘negative politeness’’ in Politeness The- could take care of the ticket here? [a fluential theory of H. P. Grice (5), or the ory). The phenomenon we address here is bribe] maintenance of ‘‘face’’ (esteem and auton- sometimes called ‘‘off-record indirect omy) in Penelope Brown and Stephen speech acts.’’ We propose a theory in This phenomenon poses a theoretical puz- Levinson’s Politeness Theory (1). Yet a three parts, which apply to interactions zle. Indirect speech is inefficient, vulnera- fundamental insight from evolutionary with successively more subtle cost–benefit ble to being misunderstood, and seemingly biology is that most social relationships structures (4). The first part is the logic of unnecessary (because only a naı¨f could involve combinations of cooperation and plausible deniability. In a simple case like fail to see past the literal meaning). Yet conflict (6, 7). This insight applies to com- bribing a police officer, the appeal of a politeness and other forms of indirectness munication among organisms no less than veiled bribe is intuitively clear: If some in speech appear to be universal or nearly to physical actions, and indeed animal officers are corrupt and would accept the so (1). We all play this game and may be signaling has been found to involve ex- bribe, but others are honest and might offended at those who don’t, setting the ploitative manipulation as well as the co- arrest the driver for bribery, an indirect stage for the hypocrisy and taboo in social operative exchange of information (8). In bribe can be detected by the corrupt cop life that are ubiquitously decried, yet ubiq- the human case, one has to think only of while not being blatant enough for the uitously obeyed. threats (the proverbial ‘‘offer you can’t honest cop to prove it beyond a reason- Indirect speech also has considerable refuse’’), dangerous secrets (hence the able doubt. A simple game-theoretic practical importance. It figures in the de- need for witness protection programs), model can delineate the circumstances in sign of computer language understanding contaminating leakage (such in blind ref- systems, which need to be programmed which indirect speech is an optimal solu- ereeing, sealed bids, and clinical trials), tion to this problem. not to take indirect requests, such as ‘‘Can and incriminating questions (for which youtellme...’’or‘‘Doyouknow...,’’ one answer might be damaging, the other literally. It is also a major bone of conten- a lie, and a refusal to answer a de facto Author contributions: S.P. and M.A.N. designed research; tion in the framing and interpretation of confession that those are the respondent’s J.J.L. performed research; J.J.L. analyzed data; and S.P. diplomatic agreements, and in the prose- two options) (ref. 9; see also Gerd Giger- wrote the paper. cution of bribery, extortion, and sexual enzer’s Law of Indispensable Ignor- The authors declare no conflict of interest. harassment. ance, www.edge.org/q2004/page2.html# This article is a PNAS Direct Submission. For 50 years, indirect speech has been gigerenzer). The very existence of indi- †To whom correspondence should be addressed. E-mail: intensively studied by linguists, philoso- rectness in language suggests that such [email protected]. phers, and psycholinguists, and the pro- adversarial dynamics might be in play in © 2008 by The National Academy of Sciences of the USA www.pnas.org͞cgi͞doi͞10.1073͞pnas.0707192105 PNAS ͉ January 22, 2008 ͉ vol. 105 ͉ no. 3 ͉ 833–838 Downloaded by guest on October 1, 2021 The second part of theory extends the would be to take care of it here’’). Sup- cide how to react to the proposition; this game-theoretic logic to social situations in pose he knows that the officer can recog- tendency can be captured by a decision which there are no fines or other tangible nize it as an intended bribe, and that the function, L, which monotonically relates costs and benefits, such as a diner without officer knows that he couldn’t make a the directness of the proposition to the a restaurant reservation who bribes a mai- bribery charge stick in court because the probability that the officer will treat it as tre d’ for a quick table, or a person who ambiguous wording would prevent a pros- an attempted bribe and act accordingly. tenders a sexual invitation to a friend af- ecutor from proving his guilt beyond a Putting these together, the expected cost ter a dinner. Unlike the driver and the reasonable doubt. The driver now has a to a driver facing a corrupt cop is yc ϭ officer, the speaker would incur no finan- third option: c0 p ϩ c1(1 Ϫ p); the cost when facing an cial or judicial penalty were the hearer to honest cop is yh ϭ c2 p ϩ c1(1 Ϫ p); alto- turn down a blatant proposition, so the Dishonest Honest gether, the driver’s expected cost is y ϭ officer officer question here is why speakers still resort qyh ϩ (1 Ϫ q)yc. to innuendo. Don’t Traffic Traffic Now, if the corrupt and honest cops The third part addresses scenarios in bribe ticket ticket share a single linear decision function which people use indirect speech even L and hence have the same p for any when the degree of uncertainty about the Bribe Go free Arrest for proposition, the optimal level of direct- other’s intentions is low—either because bribery ness will simply be determined by the variance among listeners’ values is low (so Implicate Go free Traffic fraction of honest officers. If q Ͼ (c1 speakers’ confidence in their values is bribe ticket Ϫ c0)/(c2 Ϫ c0), then the optimum high), or because the listener is astute strategy for the driver is not to make enough to understand the intent of a ϭ The payoffs in this third row com- any bribing attempt at all: d 0. If the speaker’s innuendo with high confidence. bine the very large advantage of brib- fraction of honest officers is less than Why, in such cases, is a thinly veiled prop- ing a dishonest cop with the relatively this critical value, then the optimum osition still more acceptable than a naked small penalty of failing to bribe an strategy for the driver is to make the one? The answer must pertain to some honest one.