The Morning After

2. The Morning After • October 24-26 • http://gaming.union.rpi.edu

3. Introduction to Cognition and Gaming • 10/2/02: Hawks and Doves

4. The Common Wisdom • Natural selection and the struggle for survival are the cruel laws of nature • The strongest and smartest of us will promote the survival of the species, the rest of us will die • “A man is a wolf to another man” - Platus • Is natural selection the only “force” at work in evolution?

5. Evolution • “The theory of evolution has a special characteristic: Everybody thinks they understand it!”-Jacques Monod • Evolution is a high-level natural law that describes change and stability in a world in which life already exists – deals much more with development (rather than origin) • Looking for the ultimate rational principles that govern the universe is like the guy in the army surplus store

6. The Theory of Group Selection • The initial approach was that natural selection operates at the level of the individual organism • This approach failed to explain many behaviors in nature, some of which can even be called altruistic • Sticklebacks and bees

7. The Theory of Group Selection • Darwin suggested that natural selection exerts its “force” as though the entire colony of bees were a single organism • However, characteristics useful for survival can be passed from one generation to the next only through the reproduction of individuals • Therefore, natural selection can only be the exclusive mechanism of evolution if it favors the individual as well as the group. • Self sacrifice?

8. The Theory of Group Selection • The theory states that the unit of natural selection is the larger group • When wolves fight, the winner never kills the vanquished, for it would lead to a weaker pack • If selection affects the entire species, then it can force individuals to sacrifice themselves, and those organisms with precisely those characteristics will survive (!!) • Altruism need not be pure – sticklebacks will compete amongst themselves, but competition can be good for the group

9. The Theory of Gene Selection • This theory is as logical a solution as the theory of group selection, an operates at a much smaller scale • Imagine the winning wolf standing over his defeated opponent. A demon gene appears on his shoulder and says, “Kill him! He’s a rival!” An angel gene appears on the other and says “Have mercy! You have nothing to gain from his death!”

10. The Theory of Gene Selection • Of course, genes don’t engage in such witty and sophisticated banter • Wolves nor genes need to justify their behavior – the wolf obeys the gene’s dictates, and has no more control over the situation than if it had genes for brown eyes but wanted blue • Given these two genotypes, which will favor survival?

11. The Theory of Gene Selection • The theory states that the unit of natural selection is the gene, and the struggle for survival is a competition among genes • Individual organisms are machines constructed by genes to act as vehicles to ensure the genes’ survival • The gene that finds a place for itself in a better machine is the gene that will survive

12. Theory Competition • Both theories are scientifically valid in the sense that they can be tested by experiments • Results of experimentation are highly diverse, which is expected, since quantitative predictions can only be made if the values of all possible outcomes are known

13. Is saying “Both!” a Cop-Out? • In physics, light is as it is, but can act as a particle or a wave, depending on what the experiment asks of it • In economics, most countries have a combination of state enterprises (social model) and private enterprises (free-market competition model) – their symbiosis is logically justified

14. The Struggle Between Hawks and Doves • “Suppose that there are only two sorts of fighting strategies in a population of a particular species, named hawk and dove*. Any individual of our hypothetical population is classified as either a hawk or a dove. Hawks always fight as hard and as unrestrainedly as they can, retreating only when seriously injured…. • *The names refer to conventional human usage and have no connection with the habits of the birds from whom the names are derived: doves are in fact rather aggressive birds.

15. The Struggle Between Hawks and Doves • …Doves merely threaten in a dignified conventional way, never hurting anybody. If a hawk fights a dove, the dove quickly runs away, and so does not get hurt. If a hawk fights a hawk, they go on until one of them is seriously injured or dead. If a dove meets a dove, nobody gets hurt; they go on posturing at each other for a long time until one of them tires or decides not to bother anymore, and therefore backs down.”-Richard Dawkins, The Selfish Gene, page 75

16. The Game • Let’s assume that victory scores 50 points, injury results in a loss of 100 points, and the time spend posing in a threatening manner (doves) costs 10 points • Assuming hawks win half of their battles with other hawks, they average (50 + -100)/2 = -25 points • Expected gain of dove vs. dove is ((50-10) + -10)/2 = 15

17. The Game

18. Rationality in Nature • Say there’s a proportion of 7 hawks for every 5 doves in a particular population • Hawks will encounter doves 5/12 of the time, getting 50 points each. They’ll encounter hawks 7/12 of the time, losing (on average) 25 points • (5/12 x 50) + (7/12 x -25) = 6.25 points on average • Doves in the same population will gain: • (5/12 x 15) + (7/12 x 0) = 6.25 points on average! • We have reached an evolutionary stable strategy

19. Test 2 • Monday • Same format as Test 1