Humans, unlike other animals, are equipped with a powerful brain that permits conscious awareness and reflection. A growing trend in psychological science has questioned the benefits of consciousness, however. Testing a hypothesis advanced by [Lieberman, M. D., Gaunt, R., Gilbert, D. T., & Trope, Y. . Reflection and reflexion: A social cognitive neuroscience approach to attributional inference. Advances in Experimental Social Psychology, 34, 199–249], four studies suggested that the conscious, reflective processing system is vital for logical reasoning. Substantial decrements in (...) logical reasoning were found when a cognitive load manipulation preoccupied conscious processing, while hampering the nonconscious system with consciously suppressed thoughts failed to impair reasoning . Nonconscious activation of the idea of logical reasoning increased the activation of logic-relevant concepts, but failed to improve logical reasoning performance unless the logical conclusions were largely intuitive and thus not reliant on logical reasoning . Meanwhile, stimulating the conscious goal of reasoning well led to improvements in reasoning performance . These findings offer evidence that logical reasoning is aided by the conscious, reflective processing system. (shrink)