Through his research with the rats, he learned that forgetting was dependent on the amount of tissue removed and not where it was removed from. He called this "mass action" and he believed that it was a general rule that governed how brain tissue would respond, independent of the type of learning. But we know now that mass action was a misinterpretation of his empirical results, because in order to run a maze the rats required multiple cortical areas. Cutting into small individual parts alone will not impair the rats' brains much, but taking large sections removes multiple cortical areas at one time, affecting various functions such as sight, motor coordination and memory, making the animal unable to run a maze properly.