Scientists have been working for decades on trying to build artificial intelligence. But how much progress has actually been made, when “notions as ‘water is wet’ and ‘fire is hot’ have proved elusive quarry for AI researchers? Unfortunately, the strategies most popular among AI researchers in the 1980s have come to a dead end. So-called ‘expert systems,’ which emulated human expertise within tightly defined subject areas like law and medicine, could match users’ queries to relevant diagnoses, papers and abstracts, yet they could not learn concepts that most children know by the time they are 3 years old.”