The paper studies an evolutionary model where players from a given
population are randomly matched in pairs each period to play a co-
ordination game. At each instant, a player can choose to adopt one
of the two possible behavior rules, called the rational rule and the as-
piring rule, and then take actions prescribed by the chosen rule. The
choice between the two rules depends upon their relative performance
in the immediate past. We show that there are two stable long run
outcomes where either the rational rule becomes extinct and all play-
ers in the population achieve full eciency, or that both the behavior
rules co-exist and there is only a partial use of ecient strategies in
the population. These ndings support the use of the aspiration driven
behavior in several existing studies and also help us take a comparative
evolutionary look at the two rules in retrospect