Assessing vigilance through a brief pencil and paper letter cancellation task (LCT): effects of one night of sleep deprivation and of the time of day.

Behavioural effects of the lack of sleep in normal subjects have been investigated mostly by experimenter-paced choice reaction times in prolonged stimulus detection tasks. However, length and procedure complexity of these tasks limit their use in research on larger numbers of subjects. The aim of the present study was to assess the effectiveness of a brief subject-paced pencil and paper performance task, i.e. letter cancellation task (LCT) in revealing the effects of one night of sleep deprivation. In addition, the authors evaluated sleep loss and time of day effects on six Visual Analogue Scales (VAS) measuring subjective activation-deactivation. Results show that a LCT is sensitive in revealing the effects of time of day and of 24 h of sleep deprivation. Effects of sleep deprivation were also revealed by VAS data. Sleepiness, tiredness and energy scales on the VAS were also affected by time of day. Despite the sensitivity of both the LCT and VAS, there was little correspondence between performance and subjective measures.