The effects of one night's total sleep deprivation were examined using the Wilkinson vigilance task and four 10 min duration performance tests, A repeated measures design was used in which eight male subjects experienced one night of sleep loss, the order of sleep loss being balanced across subjects, The four short duration performance tests consisted of choice reaction time, simple reaction time, short-term memory, and a motor task, handwriting, The results confirm the effects of one night's

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... eep deprivation on the vigilance task and also show that performance on the two reaction time tests was significantly impaired by the loss of sleep, but not at such a high level as for the vigilance, The short-term memory test failed to show any adverse effects of sleep loss and similarly for the handwriting, The experiment shows that two portable and brief (10 min) performance tests are sensitive indices of sleep loss and should be particularly useful for assessing levels of alertness in the field, Over the years of sleep loss research, it has been found that certain performance tests are sensitive indices of the effects of one night's loss of sleep. The sensitivity of these tests is dependent on a number of properties present in varying proportions, depending on the nature of the task (cf. review by Wilkinson, 1965) . These properties include the duration of the test, level of complexity, interest value, and the degree to which knowledge of results is available. An ideal task to show effects from loss of sleep is long, complex, uninteresting, and does not have results available to the subject. Such tasks, for example, vigilance and serial reaction tests, have been used extensively in the laboratory setting to assess the effects of sleep loss. In a world