Why cheap and ambiguous signals may serve diplomacy better than credible commitments. Commentary by Olivier Morin on Blumstein et al. (The Peacock’s Tale)

By Peter Turchin February 28, 2012 No Comments

In this interesting paper, Blumstein et al. argue for a view of diplomacy based on credible commitments, honest signals, and the prevention of misunderstandings caused by cultural distance. They hope to enlighten politicians with lessons drawn from evolutionary biology (though one might note that credible commitment was explored by Clausewitz before Darwin, and costly signalling is found in Thomas Schelling before Amos Zahavi). This comment challenges two points made by their article.

First, I argue that misdirection, ambiguity and provocation are worthy tools in a politician’s toolbox. Yes, such strategies may lead to military escalation — but sometimes that is precisely the point. I shall illustrate this with the story of the Ems dispatch, one of the most famous episodes of diplomatic signalling. Second, I will argue that Blumstein et al. misuse the notion of costly signalling, as used in economics and evolutionary biology (Zahavi, 1977). A costly signal in the strict sense is so costly to produce that the fact of producing it provides a credible information. Peacock’s tails and nuclear tests are costly signals sensu stricto. Threats, promises, symbolic gestures, and most other diplomatic moves are not costly in that sense. As a result, their informational value is different.

The Ems dispatch

In the summer of 1870, Chancellor Bismarck made a diplomatic move that would eventually make him the unifier of Germany and the victor of the Franco-Prussian war (Howard 2001). The move began when he encouraged a cousin of the King of Prussia to become candidate for the throne of Spain. A Hohenzollern in Madrid — that would mean an encirclement of France by friends of Prussia, a notoriously hostile power. Bismarck knew this. He knew this may cause violent reactions from the French, even a war in which Paris would play the part of the aggressor. Such a war would fit well into Bismarck’s plans for national unification.

Yet Napoleon III deftly defused the crisis. He uncovered Bismarck’s plan and managed to have the Hohenzollern claim to the Spanish throne withdrawn, with the agreement of the King of Prussia. A French agent went to Ems-Baden to seal the deal with the King. Bismarck, seeing his plan unravelling under his eyes, refused to be present at the meeting, and threatened to resign if the meeting took place. All in vain.

On the thirteenth of July, on the promenade of Ems, the King had a tense but courteous talk with the French ambassador. He confirmed the withdrawal of the Hohenzollern candidacy. Unbeknownst to Napoleon III, the French secretary of State had ordered the ambassador to take a hard line. The ambassador tried to push his advantage and obtain a commitment for the future. The King politely declined, and telegraphed Bismarck that the incident was over. The Chancellor did not react. He was nowhere to be found.

Bismarck was busy exploiting a mistake in the ambassador’s strategy. The King had satisfied one French request, but not the other. Bismarck cut and rephrased the King’s telegram to showcase the King’s refusal. His version of the Ems telegram, sent to major French and German newspapers, depicts a harsh and bitter encounter. Nationalists on both sides further distorted the message. The dispatch humiliated Prussia, whose King had been harassed with an arrogant ultimatum. It incensed the French, who declared war on Prussia less than a week later. Bismarck had won his first move.

The Chancellor’s tactics may interest Daniel Blumstein and his coauthors, since it turns most of their advice on its head. Bismarck did not pay attention to Blumstein et al.’s lessons 1 and 4. He produced few signals, most of them deceptive. He did not intend to resign if the Ems meeting took place. The Ems dispatch itself was a deliberately distorted signal.

Oblivious to Blumstein et al.’s lessons 2 and 3, Bismarck used historical precedent in a predictable, almost boring way. Unifying German imperial powers with the Spanish throne had been a classic geostrategic move in European history since the time of Charles V. It had always been interpreted as an attempt to isolate France, and Bismarck used this common knowledge to provoke the French.

Against lesson 8, Bismarck knew that the Ems dispatch would give rise to divergent interpretations on both sides of the Rhine, with everyone distorting and amplifying the dispatch to suit their purposes (as he himself did). Yet he did not try to limit or control the disagreements, as he did not see them as obstacles. Quite the contrary.

“Costly” signals?

Yet, one might reply, Bismarck seems to follow at least one of Blumstein et al.’s lessons. In a way, he uses “costly” signals: every time he communicates something, he takes a risk. His foreign policy is like the peacock’s tail in this respect: it is a signal with a cost.

The analogy is misleading, though. The costly signals of modern costly signalling theory are not merely signals that have a cost to the producer. The point of costly signals is that certain signals are more reliable than others since their production is costly (Veblen 1899/1973, Schelling 1960, Zahavi 1977). For instance, a peacock’s tail is a reliable indicator of a peacock’s fitness because it would be hard to grow a beautiful tail without a good immune system. Or possessing two luxury cars is a reliable indicator of wealth because possessing such cars without being wealthy would be difficult. Those signals are especially reliable because they reveal a cost that has already been paid.

Compare those costly-to-produce signals with signals that are cheap to produce, though the emitters take risks when emitting them. Uttering a sentence, in itself, is easy, whether the sentence is true or not. Lying may have costly consequences, of course, but those costs lie in the future. However near that future might be, the costs are not paid by the lier when he pronounces his lie. Thus the production of a sentence, by itself, says nothing about its truth. In contrast, the mere fact of producing a beautiful tail is a good indicator of the reproductive potential that the tail indicates.

Blumstein et al. Are right to note that politicians sometimes use such signals, like military parades or nuclear tests. But most diplomatic threats and promises are not costly signals in the biological sense. They are not costly and honest in the way a peacock’s tail is costly and honest. Bismarck’s threat to resign if the Ems meeting took place was just cheap words. His utterance of the threat was not an honest signal of his intention to resign. Indeed, nothing Bismarck could have said could be a costly signal in the biological sense.

Technical or moral advice?

Bismarck’s warmongering was, of course, objectionable in many ways. A moral person would usually prefer diplomatic strategies based on credible commitment, and a careful avoidance of escalation and misunderstandings. Since the Cold War, this way of doing politics seems the least destructive on the global scale. Yet individual politicians do not necessarily have peace and security as their first objective. Credible commitment is a useful tool for them, but sometimes ambiguity and deception serve them better. Even for peace-making: Charles de Gaulle solved the Algerian crisis by appearing utterly uncommitted and unpredictable. Thus, while I share the moral outlook of Blumstein et al. and agree with them on ethical grounds, I do not think we should commend their strategic solutions to actual politicians — unless we make it clear that we are not giving technical advice to diplomats, but promoting one particular view of what international relations should look like.


Michael Howard, 2001. The Franco-Prussian War: The German Invasion of France 1870-1871. Oxford: Routledge.

Thomas Schelling, 1960. The Strategy of Conflict. Cambridge: Harvard University Press.

Thorstein Veblen, 1899/1973. The Theory of the Leisure Class. Boston: Houghton Mifflin.

Amos Zahavi, 1977. The cost of honesty (Further remarks on the handicap principle). Journal of Theoretical Biology, 67: 603-605.

Published On: February 28, 2012

Peter Turchin

Peter Turchin

Curriculum Vitae

Peter Turchin is an evolutionary anthropologist at the University of Connecticut who works in the field of historical social science that he and his colleagues call Cliodynamics. His research interests lie at the intersection of social and cultural evolution, historical macrosociology, economic history and cliometrics, mathematical modeling of long-term social processes, and the construction and analysis of historical databases. Currently he investigates a set of broad and interrelated questions. How do human societies evolve? In particular, what processes explain the evolution of ultrasociality—our capacity to cooperate in huge anonymous societies of millions? Why do we see such a staggering degree of inequality in economic performance and effectiveness of governance among nations? Turchin uses the theoretical framework of cultural multilevel selection to address these questions. Currently his main research effort is directed at coordinating the Seshat Databank project, which builds a massive historical database of cultural evolution that will enable us to empirically test theoretical predictions coming from various social evolution theories.

Turchin has published 200 articles in peer-reviewed journals, including a dozen in Nature, Science, and PNAS. His publications are frequently cited and in 2004 he was designated as “Highly cited researcher” by Turchin has authored seven books. His most recent book is Ultrasociety: How 10,000 Years of War Made Humans the Greatest Cooperators on Earth (Beresta Books, 2016).

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