Researchers have struggled with the problem of obtaining an "accurate" operational
definition of drowsiness. Drowsiness is difficult to define because it may involve many
different indicators, such as different physiological measures. This thesis consists of two
separate, but related, experiments to determine an optimal method of determining
whether or not an individual is drowsy via physiological and observed measures. The
first part of the experiment used behaviorally trained observers to rate different subjects
on the level of drowsiness observed. The data collected showed that trained raters are
relatively consistent when rating drowsiness.
The second part of the experiment tried to determine if there is a good
physiological model to predict performance impairment due to drowsiness by collecting
data on sleep deprived subjects. The subjects were given two interleaved tasks, low level
and high level cognitive tasks, to perform while twenty-one performance and behavioral
measures were collected. The results show that a regression model can be developed using eyelid closure measures, simple EEG measures and simple heart-rate measures to predict performance impairment due to drowsiness.
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