Human brains seem to accomplish tasks in ways that would require absurd amounts of computer power if they were to be duplicated by machines. The first expert-systems experiments were not focused exclusively on machine capabilities nor on human capabilities, but on the border between the two types of symbol processors. How could a machine be used to transfer expertise from one human to another? The emerging differences between machine capabilities and human cognitive talents were brought into sharper focus when it was demonstrated by systems like MYCIN that this kind of software was capable of measurably augmenting the power of human judgment. Doctors who used MYCIN to aid their diagnostic decision-making ended up making accurate diagnoses more often than they did before they used the program to assist them.