Game theory analysis shows how evolution favors cooperation's collapse

Last year, University of Pennsylvania researchers Alexander J. Stewart and Joshua B. Plotkin published a mathematical explanation for why cooperation and generosity have evolved in nature. Using the classical game theory match-up known as the Prisoner's Dilemma, they found that generous strategies were the only ones that could persist and succeed in a multi-player, iterated version of the game over the long term.

But now they've come out with a somewhat less rosy view of evolution. With a new analysis of the Prisoner's Dilemma played in a large, evolving population, they found that adding more flexibility to the game can allow selfish strategies to be more successful. The work paints a dimmer but likely more realistic view of how cooperation and selfishness balance one another in nature.

"It's a somewhat depressing evolutionary outcome, but it makes ," said Plotkin, a professor in Penn's Department of Biology in the School of Arts & Sciences, who coauthored the study with Stewart, a postdoctoral researcher in his lab. "We had a nice picture of how evolution can promote cooperation even amongst self-interested agents and indeed it sometimes can, but, when we allow mutations that change the nature of the game, there is a runaway evolutionary process, and suddenly defection becomes the more robust outcome."

Their study, which will appear in the Proceedings of the National Academy of Sciences, examines the outcomes of the Prisoner's Dilemma, a scenario used in the field of to understand how individuals decide whether to cooperate or not. In the dilemma, if both players cooperate, they both receive a payoff. If one cooperates and the other does not, the cooperating player receives the smallest possible payoff, and the defecting player the largest. If both players do not cooperate, they both receive a payoff, but it is less than what they would gain if both had cooperated. In other words, it pays to cooperate, but it can pay even more to be selfish.

Stewart and Plotkin's previous study examined an iterated and evolutionary version of the Prisoner's Dilemma, in which a population of players matches up against one another repeatedly. The most successful players "reproduce" more and pass along their winning strategies to the next generation. The researchers found that, in such a scenario, cooperative and even forgiving strategies won out, in part because "cheaters" couldn't win against themselves.

In the new investigation, Stewart and Plotkin added a new twist. Now, not only could players alter their strategy—whether or not they cooperate—but they could also vary the payoffs they receive for cooperating.

This, Plotkin said, may more accurately reflect the balancing of risk and reward that occurs in nature, where organisms decide not only how often they cooperate but also the extent to which they cooperate.

Initially, as in their earlier study, cooperative strategies found success.

"But when cooperative strategies predominate, payoffs will rise as well," Stewart said. "With higher and higher payoffs at stake, the temptation to defect also rises. In a sense the cooperators are paving the way for their own demise."

Indeed, Stewart and Plotkin found that the population of players reached a tipping point after which defection was the predominant strategy in the population.

In a second analysis, they allowed the payoffs to vary outside the order set by the Prisoner's Dilemma. Instead of unilateral defection winning the greatest reward, for example, it could be that mutual cooperation reaped the greatest payoff, the situation described by a game known as Stag Hunt. Or, mutual defection could generate the lowest possible reward, as described by the game theory model known as the Snowdrift or Hawk-Dove game.

What they found was that, again, there was an initial collapse in cooperative strategies. But, as the population continued to play and evolve, players also altered the payoffs so that they were playing a different game, either Snowdrift or Stag Hunt.

"So we see complicated dynamics when we allow the full range of payoffs to evolve," Plotkin said. "One of the interesting results is that the Prisoner's Dilemma game itself is unstable and is replaced by other games. It is as if evolution would like to avoid the dilemma altogether."

Stewart and Plotkin say their new conception of how strategies and payoffs co-evolve in populations is ripe for testing, with the marine bacteria Vibrionaceae as a potential model. In these bacterial populations, the researchers noted, individuals cooperate by sharing a protein they extrude that allows them to metabolize iron. But the bacteria can possess mutations that alter whether they produce the protein and how much they generate, whether and how much they cooperate, as well as mutations that affect how efficiently they can take up the protein, their payoff. The Penn researchers said a "natural experiment" using these or other microbes could put their theory to the test, to see exactly when and how selfishness can pay off.

"After this study, we end up with a less sunny view of the evolution of cooperation," Stewart said. "But it rings true that it's not the case that evolution always tends towards happily ever after."


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Generosity leads to evolutionary success, biologists show

More information: Collapse of cooperation in evolving games , PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1408618111
Citation: Game theory analysis shows how evolution favors cooperation's collapse (2014, November 24) retrieved 21 September 2019 from https://phys.org/news/2014-11-game-theory-analysis-evolution-favors.html
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Nov 24, 2014
Does this mean conservatives will eventually win?

Nov 24, 2014
Human development was driven by group selection. Groups which had greater internal cohesion and cooperation coupled with concerted external animosity would tend to prevail in intertribal conflict.
http://rechten.el...RID2.pdf

This study might be true for other animals but it does not apply to humans.

Nov 24, 2014
No this doesn't mean that "conservatives will eventually win", especially considering that they never alter their theories based upon measured results. What it means is that (as Nash predicted) the 'best' strategy for virtually any complex 'game' is likely a mix of selfishness and cooperation, and that the mix will vary based upon how deep the system feedback goes. First level feedback (i.e. players change their strategy based upon the perceived strategy of the opponent) has one type of impact, but what we see here is that deeper feedback (i.e. players actually change the basic game itself based on results) has a different impact. Either way, anyone who thought that a purely cooperative strategy would work best was kidding themselves. The world of humans is not as simple as an ant colony, or a flock of birds, or even a pack of wolves or group of Apes vying for dominance. We know that feedback exists, and realize others know it too...

Nov 24, 2014
Either way, anyone who thought that a purely cooperative strategy would work best was kidding themselves. The world of humans is not as simple as an ant colony, or a flock of birds, or even a pack of wolves or group of Apes vying for dominance
Consider football. Teams who are better able to cooperate in the execution of complex plays can be expected to win games.

Consider war. Armies composed of individuals who are more willing to trust their leaders, and to sacrifice themselves for their fellow soldiers, can be expected to win out on the battlefield.

No place for selfishness in either.

Nov 24, 2014
I disagree, human societal movement may be driven by cohesion and co-operation, especially with an outside antagonist, however, the individuals provided with the greatest ability to enjoy the product of societies efforts will be those exercising the mechanism of defection/predation.

It's Poker on a grand scale, you cannot play the game without someone at the table ending up with more chips than the others, metaphorically, you cannot breed, cannot have comfort, enjoyment and ego without achieving some kind of measurable success comparable to those around you.

Nov 24, 2014
The prisoner's dilemma is crap.
GIGO.

" evolution always tends towards happily ever after.""
More crap.

Nov 24, 2014
"We had a nice picture of how evolution can promote cooperation even amongst self-interested agents "
Incorrect assumption.
ALL life is 'self-interested' in survival.
Too bad so many 'academics' are socialists and have likely don't understand or have read Adam Smith or Mises.
Cooperation occurs when it is in one's self interest to cooperate. Humans can consciously make this choice and other life forms evolve to it, until something changes.

Nov 24, 2014
ALL life is 'self-interested' in survival.


Incorrect = http://en.wikiped...ll_death

rgw
Nov 30, 2014
Never bet on anything that needs to eat.

Nov 30, 2014
ALL life is 'self-interested' in survival.


Incorrect = http://en.wikiped...ll_death


"PCD is carried out in a regulated process, which usually confers advantage during an organism's life-cycle"
Self interest.
Parents will sacrifice themselves to save their offspring and promote the self-interested survival of their genes.

Nov 30, 2014
Never bet on anything that needs to eat.


I think the rule is that Philosophy for the sake of Philosophy is a waste of time if there are more pressing matters, like eating. No one is a saint when their stomach is growling.

Nov 30, 2014
The classic game theory example of the 'prisoner's dilemma' is a limited abstraction of reality and the results of such a model should be treated accordingly.
No one discusses why A and B are prisoners. Are they members of the French underground in a Gestapo prison? Are they POWs in Hanoi Hilton? Are they Jews in Dachau? Are they family members with one trying to protect the other?

Dec 21, 2014
Self interest.
Parents will sacrifice themselves to save their offspring and promote the self-interested survival of their genes.


Incorrect, a cell is a living entity, programmed to self destruct for the continued survival of the organism as a whole. Using this as a metaphor, individual human beings can be blood cells in the social organism, where an individual may be programmed to die/suicide in order to protect the organism as a whole.

http://en.wikiped..._despair
http://psychclass...love.htm

http://www.youthb...nd-facts
http://www.mindfr...nd-stats

Human behaviour is not particularly different to animal behaviour, you are just another cell in the societal organism, "you are not a beautiful unique snowflake".

Consider logically, why would suicide exist without a reason? Wouldn't that reason be linked to biology?

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