Signaling under Common and Conflicting Interests IRCS Common Ground - PowerPoint PPT Presentation

Conflicts Signaling Games Cycles Conclusions Signaling under Common and Conflicting Interests IRCS Common Ground Seminar Christopher Ahern Joint work with Robin Clark University of Pennsylvania September 18, 2013 Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 1 / 48

Conflicts Signaling Games Cycles Conclusions Goals Effect of conflicting interests on signaling in a population. What does conflict do? How do we use signals? Where does language go? Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 2 / 48

Conflicts Signaling Games Cycles Conclusions Talk Outline Conflicts 1 Signaling 2 Games 3 Cycles 4 Conclusions 5 Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 3 / 48

Conflicts Signaling Games Cycles Conclusions Philosophy Hobbes (1651) In such condition there is no place for industry, because the fruit thereof is uncertain, and consequently, not culture of the earth,... no arts, no letters, no society, and which is worst of all, continual fear and danger of violent death, and the life of man, solitary, poor, nasty, brutish, and short. Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 4 / 48

Conflicts Signaling Games Cycles Conclusions Philosophy Locke (1690) The state of nature has a law of nature to govern it, which obliges every one: and reason, which is that law, teaches all mankind, who will but consult it, that being all equal and independent, no one ought to harm another in his life, health, liberty, or possessions. Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 5 / 48

Conflicts Signaling Games Cycles Conclusions Philosophy Hobbes: Better at self-promotion Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 6 / 48

Conflicts Signaling Games Cycles Conclusions Philosophy Leviathan: Better album name Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 7 / 48

Conflicts Signaling Games Cycles Conclusions Biology Tennyson (1850) Who trusted God was love indeed And love Creation’s final law– Tho’ Nature, red in tooth and claw With ravine, shriek’d against his creed– Who loved, who suffer’d countless ills, Who battled for the True, the Just, Be blown about the desert dust, Or seal’d within the iron hills? Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 8 / 48

Conflicts Signaling Games Cycles Conclusions Biology Dawkins (1976) We are survival machines – robot vehicles blindly programmed to preserve the selfish molecules known as genes. Any altruistic system is inherently unstable, because it is open to abuse by selfish individuals, ready to exploit it. Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 9 / 48

Conflicts Signaling Games Cycles Conclusions Biology Richard Dawkins and the Selfish Gene: Good band name Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 10 / 48

Conflicts Signaling Games Cycles Conclusions Crucial points for Signaling Cooperation 1 Honesty 2 Mechanisms 3 Language 4 Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 11 / 48

Conflicts Signaling Games Cycles Conclusions Cooperation Nowak (2006) Cooperation means that selfish replicators forgo some of their reproductive potential to help one another. But natural selection implies competition and therefore opposes cooperation unless a specific mechanism is at work. Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 12 / 48

Conflicts Signaling Games Cycles Conclusions Honesty Searcy & Nowicki (2005) One might expect many instances in which signalers would attempt to profit individually by conveying dishonest information. ...if dishonesty is common, it also is not obvious why receivers should respond to signals. ...if receivers fail to respond to signals, it is not obvious how signaling systems can exist at all. Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 13 / 48

Conflicts Signaling Games Cycles Conclusions Mechanisms Scot-Phillips (2008) Indices: signal form is tied to meaning 1 Handicaps: costs borne by honest senders 2 Deterrents: costs borne by dishonest senders 3 Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 14 / 48

Conflicts Signaling Games Cycles Conclusions Mechanisms Reby & McComb (2003) Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 15 / 48

Conflicts Signaling Games Cycles Conclusions Mechanisms Zahavi (1975) Grafen (1990) Spence (1973) Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 16 / 48

Conflicts Signaling Games Cycles Conclusions Mechanisms Dostoyevsky (1866) Where is it I’ve read that someone condemned to death says or thinks, an hour before his death, that if he had to live on some high rock, on such a narrow ledge that he’d only room to stand, and the ocean, everlasting darkness, everlasting solitude, everlasting tempest around him, if he had to remain standing on a square yard of space all his life, a thousand years, eternity, it were better to live so than to die at once. Only to live, to live and live! Life, whatever it may be! Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 17 / 48

Conflicts Signaling Games Cycles Conclusions Mechanisms Mencken (1949) Conscience is the inner voice that warns us somebody may be looking. Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 18 / 48

Conflicts Signaling Games Cycles Conclusions Language Grice (1967) Make your conversational contribution such as is required, at the stage at which it occurs, by the accepted purpose or direction of the talk exchange in which you are engaged. Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 19 / 48

Conflicts Signaling Games Cycles Conclusions Language Grice (1967) I am, however, enough of a rationalist to want to find a basis that underlies these facts, undeniable though they may be; I would like to be able to think of the standard type of conversational practice not merely as something that all or most do in fact follow but as something that it is reasonable for us to follow, that we should not abandon. Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 20 / 48

Conflicts Signaling Games Cycles Conclusions Crucial points for Games Signaling Games 1 Nash Equilibria 2 Evolutionarily Stable Strategies 3 Parametrization 4 Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 21 / 48

Conflicts Signaling Games Cycles Conclusions Signaling Games Lewis (1969) One if by land, two if by sea. Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 22 / 48

Conflicts Signaling Games Cycles Conclusions Signaling Games δ t land t sea S S m one m two m one m two R R R R a land a sea a land a sea a land a sea a land a sea 1 , 1 0 , 0 1 , 1 0 , 0 0 , 0 1 , 1 0 , 0 1 , 1 Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 23 / 48

Conflicts Signaling Games Cycles Conclusions Signaling Games Sender observes some state of the world, t ∈ T , given probability distribution over states, δ . Sender chooses message, m ∈ M , based on strategy s ∈ [ T → M ] . Receiver interprets message with action, a ∈ A , based on strategy r ∈ [ M → A ] . U S and U R are the utility functions that define preferences over T × A . Expected utility of sender and receiver: EU S ( s , r ) = ∑ δ ( t ) · U S ( t , r ( s ( t ))) t (1) EU R ( s , r ) = ∑ δ ( t ) · U r ( t , r ( s ( t ))) t Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 24 / 48

Conflicts Signaling Games Cycles Conclusions Nash Equilibria Nash (1950, 1951) A strategy profile � s ∗ , r ∗ � is a Nash equilibrium if and only if: ∀ s ∈ S , such that s � = s ∗ , EU S ( s ∗ , r ∗ ) ≥ EU S ( s , r ∗ ) ∀ r ∈ R , such that r � = r ∗ , EU R ( s ∗ , r ∗ ) ≥ EU S ( s ∗ , r ) “Something that it is reasonable for us to follow.” -Grice Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 25 / 48

Conflicts Signaling Games Cycles Conclusions Evolutionarily Stable Strategies Maynard Smith & Price (1973) An Evolutionarily Stable Strategy is a strategy that, if all the members of a population adopt it, then no mutant strategy could invade the population under the influence of natural selection Ahern (UPENN) Signaling under Common and Conflicting Interests September 18, 2013 26 / 48