Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Mechanisms for Enforcing Honest Signaling Christopher Ahern cahern @ ling . upenn . edu University of Pennsylvania, Department of Linguistics and Institute for Research in Cognitive Science August 8, 2012 Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 1 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Goals Explore mechanisms that might keep human signaling honest. What is honesty? Should honesty in signaling evolve? persist? What, if anything, makes humans honest? What does this have to say about the study of communication and meaning? Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 2 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Talk Outline Honest Signaling 1 Signaling with Partial Common Interest 2 Possible Mechanisms 3 Conclusion 4 Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 3 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Section Outline Questions to answer 1. What is the relevant notion of honesty? 2. How does it relate to the study of meaning? Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 4 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Honesty What is Honesty? Honesty (Searcy & Nowicki, 2005) Honesty is the absence of deception. Deception occurs when a Sender sends a signal to a Receiver and: 1. the Receiver responds in a way that benefits the Sender 2. the response is appropriate if the signal reliably indicates a situation, X, and 3. it is not the case that X obtains Relationship to Cooperation Requires cooperation on the part of senders. Senders must forgo some benefit to use signals honestly. Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 5 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Honesty When is Cooperation/Honesty Possible? A B Work Shirk A 1,1 0,0 Work 3,3 0,4 B 0,0 1,1 Shirk 4,0 2,2 Cooperation is possible in Work-Shirk (Right), but not in Pure Coordination Game (Left). Would an A-player say, “I am going to play B!”? Would anyone believe, “I am going to Work!”? Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 6 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Deception Deception and the Evolution of “Meaning” Deception Undermines “Meaning” Assuming that deception involves a loss on the part of the receiver, if individuals have incentive to deceive each other then conventional signaling is counter-selected for (Zahavi, 1993). Signals cease to reliably correlate with any aspects of the sender or the environment. Credulous receivers do worse than skeptical ones. Skeptical receivers do not attend to signals. Senders should not signal if receivers do not attend to signals. Signaling should disappear under the effects of deception. Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 7 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Deception How do we get to where we are? Grice’s (1975) Maxim of Quality Try to make your contribution one that is true. (1) Do not say what you believe is false. (2) Do not say that for which you lack adequate evidence. More generally Words are meaningful. We might ask what sorts of social and cognitive mechanisms allow them to be so. Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 8 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Section Outline Questions to answer 1. What is the formal apparatus we are using? 2. What is a reasonable game structure? 3. What are the results? Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 9 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Signaling Games Signaling Games Signaling Game: �{ S , R } , T , δ , M , A , U S , U R � S is the sender, and R is the receiver. T is a set of states δ is a probability distribution over those states M is a set of messages A is a set of actions U S and U R are the utility functions of S and R Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 10 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Signaling Games Signaling Games Structure of play Sender observes a state t ∈ T , determined by δ . Sender chooses a message m ∈ M based on a strategy s ∈ [ T → M ] which is transmitted to the receiver. Receiver takes an action a ∈ A based on the message received and a strategy r ∈ [ M → A ] . Payoffs for S and R are determined by the type t , message sent s ( t ) , and action taken r ( s ( t )) . Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 11 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Signaling Games Signaling Games in Extensive Form δ t 1 t 2 S S m 1 m 2 m 1 m 2 R R R R a 1 a 2 a 1 a 2 a 1 a 2 a 1 a 2 Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 12 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Example Ralph Likes: tasty fruit, going for long swings on the vine Dislikes: non-tasty fruit, being lied to Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 13 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Example Sally Likes: tasty fruit, going for long swings on the vine Dislikes: non-tasty fruit, being lied to Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 14 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Example A match made in heaven? Sally approaches Ralph and suggests... He forage in the bushes with her for fruit. He lift her up into a tree to get tasty fruit for both of them. Ralph can... Ignore Sally entirely Forage in the bushes Lift her into the tree Sally responds to.. being ignored by moving on. an agreement to forage by foraging. being lifted up into the tree by... Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 15 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Example Take another look Sally Is Sally a cute clapping chimpanzee? Or is she scheming on some darker purpose? Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 16 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Example Suppose there are two kinds of Sally Honest Sally Will gather as much fruit as possible and drop it down for both to share. Dishonest Sally Will eat as much fruit as possible without dropping any down for Ralph. A problem for Ralph How much effort should he put into cooperating with Sally based on the signal sent? Does it reveal whether she will actually get fruit for both? Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 17 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Example Preferences for Sally Honest Sally Prefers that Ralph lift her into the tree to anything else. Prefers foraging in the bushes with Ralph to being ignored. Dishonest Sally Prefers foraging in the bushes to being lifted into the tree. She cannot eat that much before being found out by Ralph and the risk of being hurt when he finds out is sufficient to outweigh most of the benefit of the tasty fruit. Being ignored is least preferable. Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 18 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Example Preferences for Ralph For Honest Sally Exact same preferences as Honest Sally. Lifting her up into the tree is better than foraging is better than ignoring. For Dishonest Sally Ignoring is best as it leaves Ralph in a position to listen to or interact with honest senders. Foraging is better than lifting because it results in something rather than nothing. Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 19 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Example A stand-in payoff structure Payoffs a 0 a pe a e t h 0,3 5,5 8,8 t d 0,6 5,5 3,0 T = { t h , t d } (honest, dishonest sender) A = { a 0 , a pe , a e } (expend no effort and ignore, expend some proportion of effort p to forage in the bushes, expend all energy to lift) Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 20 / 50
Honest Signaling Signaling with Partial Common Interest Possible Mechanisms Conclusion Example Bad news Payoffs a 0 a pe a e t h 0,3 5,5 8,8 t d 0,6 5,5 3,0 The only equilibria of the game are pooling If types send different messages, t d can benefit by sending the same signal as t h . In response to this, receivers should play a pe . Honest senders cannot unilaterally change strategy to benefit. Ahern (IRCS) Mechanisms for Enforcing Honest Signaling August 8, 2012 21 / 50
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