This Phase I SBIR proposal is aimed at developing a non-invasive, optical method for monitoring the state of consciousness of crew members in operational environments. Utilizing differences in wavelength-dependent optical absorption between oxygenated and deoxygenated blood, pulsed laser diodes of selected wavelengths and symmetrically-placed photodetectors will be used to monitor the scattered light signals. Changes between these light signals and those established by prior baseline measurements will be monitored and interpreted using appropriate algorithms. Continuous monitoring of the mental state of personnel engaged in critical activities could provide a means of protection against human performance lapses resulting from unforeseen circumstances. Operational crew members are often subject to stress, increasing the possibility of operator mistakes or oversight. If a deterioration of the state of consciousness of an individual can be detected before that individual?s performance is affected, serious accidents or lapses in operator performance could be avoided. Phase I will establish feasibility, and Phase II will produce and evaluate a prototype monitoring instrument.