The goals of this research were to substantiate the existence of the cry-wolf effect for alarm responses, quantifying its effect on operator performance. A total of 138 undergraduate students performed two blocks of a cognitively demanding psychomotor primary task; at the same time, they were presented with alarms of varying reliabilities (25, 50 and 75% true alarms) and urgencies (green, yellow and red visual alarms presented concurrently with low-, medium- and high-urgency auditory civilian aircraft cockpit alarms). Alarm response frequencies were observed and analysed, and t-tests and repeated-measures MANOVAs were used to assess the effects of increasing alarm reliability on alarm response frequencies, speed and accuracy. The results indicate that most subjects (about 90%) do not respond to all alarms but match their response rates to the expected probability of true alarms (probability matching). About 10% of the subjects responded in the extreme, utilizing an all-or-none strategy. Implications of these results for alarm design instruction and further research are discussed.

Threshold elevations (TE) The few studies that have dealt with problems of intrasensory interaction on the skin with the standard masking procedure have confined stimulation to a relatively circumscribed area of the body, i.e., the fingers, hands, and forearms (Halliday

As automation becomes more prevalent in complex task systems, operators are confronted with a myriad of emergency signals. Although much research has been performed to improve the structure and function of signalling systems, it has concerned mainly those stimuli that are presumed to accurately indicate danger. The current report discusses the general area of emergency signal failure, its implications for complex task performance, and recommendations for design and research. A general description of the problem is followed by a review of the applicability of scienti® c theory to human behaviour during and following signal failure, and the authors conclude with recommendations for personnel training and warning signal design and research.

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Technology advances and increased application of UAVs will demand greater attention to human factors concerns in design, deployment, and training.