ECS System 1 or Effortful Control System is the system dealing with complex thinking. It can follow rules, compare objects on several attributes, and make deliberate choices between options<ref>Khanman D., 2011, Thinking fast, Thinking slow p. 36</ref>.

It is part of [http://en.wikipedia.org/wiki/Dual_process_theory two systems of decision making], the first is the automatic-system([[ASSystem 1|system 1]]) which decide fast by intuition and the second is the ECS which produce reasoning.The term system 1 and system 2 was given by Stanovich and West<ref>Stanovich KE, West RF., Individual differences in reasoning: implications for the rationality debate? Behav Brain Sci. 2000 Oct;23(5):645-65; discussion 665-726.</ref>