Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Conflict Resolution • Threat-display contests – Hawk-dove-bully – Hawk-dove-assessor • Variable length contests – War-of-attrition – Sequential assessment • Variable sequence contests Dove-Bully Game Actor: Opponent: Bully Dove Bully Dove V V/2 V/2 0 If V = 2 then Opponent: Bully Actor: Bully Dove Bully is a pure ESS 1 0 Dove 2 1 Hawk-Bully Game Opponent: Bully Actor: Bully Hawk V/2 V If V = 2, C = 4 then Opponent: Bully Actor: Bully Hawk 1 2 Hawk 0 (V-C)/2 Hawk 0 -1 Yes, Hawks can invade Bullies, but Bullies invade Hawks Therefore, this is a mixed ESS Correlated asymmetry • Opponents differ in RHP • Example: hawk - dove - assessor – Assessor strategy: if larger play hawk, if smaller play dove – If owner and intruder are equally frequent and get equal payoffs: Opponent: Actor: Hawk Dove Assessor Hawk Dove Assessor (V-C)/2 0 V/2 V V/2 3V/4 (V-C)/2 V/4 V/2 When there is a cost to fighting, Assessor is pure ESS assuming that assessment is costless and accurate Calling in toads War of attrition - the waiting game • Assumptions – Resource cannot be shared – Cost of display increases with length of contest – No information is received during contest and opponents are symmetrical – Winner is the contestant willing to accept the higher cost – The cost to both contestants equals the cost acceptable to the loser – The range of actions of each contestant is continuous War of attrition - Payoff matrix xi = amount of time individual i displays k = rate at which costs are expended V = value of resource Payoff to: Actor : xA > xB Opponent: xA < xB Player A V - kxB - kxA Player B - kxB V - kxA No pure ESS is possible, since an opponent that displayed a little bit longer would have higher fitness Solution is a mixed ESS where the probability of leaving at any time is a constant. The times an individual stays should be distributed as a negative exponential. Asymmetric war-of-attrition • If animals experience different costs of display or the resource differs in value to them, the game is asymmetric • Which player has the largest V/k will win, but this may not be known • This may lead to two different giving up time strategies War-of-attrition solutions Fight duration and resource value in newts Males fight longer over larger females. Larger females carry more eggs and are, therefore, more valuable. Sequential assessment • Assumptions – Animals display in order to acquire information about each other’s fighting ability and resource value – Fights only occur when animals are closely matched • Predictions – Fight duration increases as the asymmetry in fighting ability decreases and/or as resource value increases – The cost of a fight increases as the asymmetry in fighting ability decreases – Probability of winning increases with asymmetry Sequential assessment ESS War of attrition in spiders Resource value equal Ownership effects in spider fights War of attrition in spiders Assessment in red deer Jumping spider contest stages Sequential assessment in phases Sequential assessment in cichlids Why give multiple signals? • Each display serves a different function • Signal erosion: threat displays lose effectiveness as the frequency of bluff increases • Displays transmit graded information about display intentions – Multiple signals may lower potential risk associated with escalation Cricket display costs Little blue penguin fights Cave dwellers use more displays, but have lower escalated fights Little blue penguin display repertoire