ABSTRACT
Machines are superior to humans in monitoring roles wherever the criteria for significant monitored events or signals can be specified in machine-recognizable terms. A common outcome of the provision of computer assistance is the conversion of active human roles and tasks into more passive ones, of which monitoring is an example. Many advanced forms of computer assistance possess this fundamental property that they can disguise human inadequacy and shelter human incompetence. Decisions about human and machine initiatives can have profound human factors implications, which are seldom recognized at the time and therefore have to be coped with retrospectively. New forms of computer assistance proposed for air traffic control do not generally start from human roles but require adaptation to them, which increases the potential for mismatches between human and machine roles and for mismatches among the human roles that have become machine assisted.
