We study evolutionary Cournot games under heterogenous learning rules with their evolutionary selection driven by perturbed best-reply dynamics. While focusing on the interplay between adaptive and ‘fictitious play’ expectations, other rules ecologies are explored, too.
Our findings suggest that a population of fictitious players could be destabilized away from the Cournot-Nash equilibrium by the presence of the adaptive players. This set-up is used to build an evolutionary approach to Theocharis (1960) work on the stability of the Cournotian equilibrium. Number of players instability thresholds are derived with Theocharis’ “unstable triopoly” result obtained in the limit of naive but homogenous expectations. Last, an example of instability in the Bertrand price competition will be presented.