BIO150Y: Evolution of Cooperation Evolutionary Game

Expt. 2: Can nice strategies beat out nasty strategies?

Your Objective

Conduct simulations of a population initially composed of an equal mix of cheats (ALLD), tit for tat (TFT), grudgers (GRU) and random (RND) to determine which strategies tend to be more successful in the long-term.

Suggested Methods

  • Conduct replicates.
  • You can download a worksheet (as a PDF file) which contains data tables to record your results.
  • Based on your results, answer the quiz questions below.


  • Each coloured graph line tracks the number of players for each strategy through the 20 generations that the experiment takes.
  • Point+click on Reset to set up each new replicate experiment.


Based on your results, answer the following questions:

In a mixed population where initialy TFT, Grudger, ALLD and Random are at equal frequency, which strategies are the most successful long-term?

In a population composed of TFT, Grudger, ALLD and Random, which strategies are nice and which are nasty?

What are the characteristics of a very successful strategy in in the Prisoner's Dilemma Game?

" A nice strategy like Tit for Tat does well in a mixed population, but is it tough enough to invade and persist in a population initially dominated by nasties? Let's find out... "

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