‘raise the stakes’ evolves into a defector

ABSTRACT To understand how cooperation can evolve by reciprocal altruism when individuals can make variable investments, Roberts and Sherratt1 have introduced a new strategy, ‘raise the

stakes’ (RTS), for a continuous version of the iterated ‘prisoner's dilemma’. An individual investing _I_ bears a cost _I_, while the recipient gets a benefit _kI_. For _k_>1, this

generalizes the standard prisoner's dilemma2,5. Over _R_ alternating encounters6,7, RTS is defined as follows: on the first move, invest _a_, subsequently raise your investment by 2_b_

(or _b_) if your partner's previous investment bettered (or equalled) your last move, otherwise match your partner's last move. This strategy is denoted by σ=(_a_,_b_). Roberts and

Sherratt1 reported that the strategy σ=(1,1) performs well in computer simulations against various alternative strategies but did not consider how a population of RTS strategies with

different _a_ and _b_ values evolves. We find that selection within RTS populations always acts to lower the values of _a_ and _b_, hence RTS cooperation is not a robust phenomenon. Access

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_The Evolution of Cooperation_ (Basic, New York, 1984). * Nowak, M. & Sigmund, K. _Nature_ 355, 250–253 (1992). Google Scholar  * Nowak, M. & Sigmund, K. _Nature_ 364, 56–58 (1993).

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Scholar  Download references AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Zoology Institute, University of Basel, Rheinsprung 9, Basel, 4051, Switzerland Timothy Killingback & Michael

Doebeli Authors * Timothy Killingback View author publications You can also search for this author inPubMed Google Scholar * Michael Doebeli View author publications You can also search for

this author inPubMed Google Scholar RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Killingback, T., Doebeli, M. ‘Raise the stakes’ evolves into a

defector. _Nature_ 400, 518 (1999). https://doi.org/10.1038/22913 Download citation * Issue Date: 05 August 1999 * DOI: https://doi.org/10.1038/22913 SHARE THIS ARTICLE Anyone you share the

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