Artificial intelligence is the simulation of human intelligence processes by machines, especially computer systems. Specific applications of AI include expert systems, natural language processing, speech recognition and machine vision. The term “artificial intelligence” had previously been used to describe machines that mimic and display “human” cognitive skills that are associated with the human mind, such as “learning” and “problem-solving”. This definition has since been rejected by major AI researchers who now describe AI in terms of rationality and acting rationally, which does not limit how intelligence can be articulated.