“…For example, while Wierwille, Rahimi, & Casali (1995) found increases in blink rate when the navigational demands of a simulated flight mission increased, Stern and Skely (1984) observed decreases in blink rate when a copilot took command of an aircraft and Sirevaag et al (1988) found decreases in blink rate when subjects transitioned from a single to a dual task. While these discrepancies might be explained in terms of the visual requirements of the tasks (e.g., in both the Sirevaag et al and the Stem and Skelly studies, the visual processing demands increased in the more difficult conditions, while the visual processing requirements were essentially the same in the different navigational load conditions in the Wierwille et al study), other investigators have failed to find a significant relationship between blink rate and processing demands in a variety of visual and auditory tasks (Bauer et al, 1985;Casali & Wierwille, 1983). Thus, based on these findings, it appears that additional empirical and theoretical effort is required before blink rate couid be recommended as a measure of mental workload.…”