One of the methods used by behavioral geneticists is selective breeding. Selective breeding often involves selecting animals that are very different on one measure of behavior. For instance, if scientists take 20 rats and test how quickly they can solve a maze, chances are that they will get some variability in the speed with which the rats can solve the maze. Scientists would take the two fastest animals and the two slowest animals and breed them together. They would continue to do this over 20 generations, until they had a group of animals that solved the maze very rapidly and a group of animals that solved the maze very slowly. They are then able to examine potential differences in their brains and behaviors that contribute to maze solvi ...