automation complacency has been defined as "poorer detection of system malfunctions under automation compared with under manual control." nasa's aviation safety reporting system (asrs) defines complacency as "self-satisfaction that may result in non-vigilance based on an unjustified assumption of satisfactory system state." several studies have indicated that it occurs most often when operators are engaged in both manual and automated tasks at the same time. in turn, the operators' perceptions of the automated system's reliability can influence the way in which the operator interacts with the system. endsley (2017) describes how high system reliability can lead users to disengage from monitoring systems, thereby increasing monitoring errors, decreasing situational awareness, and interfering with an operator's ability to re-assume control of the system in the event performance limitations have been exceeded. this complacency can be sharply reduced when automation reliability varies over time instead of remaining constant, but is not reduced by experience and practice. both expert and inexpert participants can exhibit automation bias as well as automation complacency. neither of these problems can be easily overcome by training.