Evolutionarily Unstable Nash Equilibrium

This video explains how to figure out whether a mixed strategy Nash equilibrium is stable or unstable. This example is unstable.

[@paulw628]

It seems odd that when an A meets an A, one scores 4 and one scores 0; and similarly for a B meeting a B. And also, when an A meets a B the row player gets 0 and the column player gets 4 regardless of which is A and which is B.