In 1997, IBM's Deep Blue beat world chess champion Garry Kasparov. In 2016, AlphaGo beat Lee Sedol at Go. These were milestones in artificial intelligence — the simulation of human intelligence processes by computer systems. AI includes learning, reasoning, problem-solving, perception, and language understanding.

Modern AI is mostly narrow. It excels at one task: recognizing faces, translating text, recommending videos. General AI, which could handle any intellectual task a human can, does not exist yet. Researchers debate whether it ever will.

Major subfields

• Machine learning: systems that improve from data
• Natural language processing: understanding and generating text
• Computer vision: interpreting images and video
• Robotics: embodied AI that acts in the physical world

AI raises hard questions. Who is accountable when a self-driving car crashes? How do we prevent biased algorithms from denying loans or jobs? The technology is powerful. The rules for using it are still being written.