The effect of expectancy on objective and subjective measures of daytime sleepiness

The expectation of receiving a substance that participants expect will improve their sleep has been shown to effect various measures of sleep behaviour. However, most previous research has compared placebo against an active pharmaceutical agent. The present study aimed to establish if expectancy alone was sufficient to influence sleep behaviour and subsequent daytime sleepiness. Pupillometry was used to measure daytime sleepiness (using the Pupillographic Sleepiness Test: PST). The Stanford Sleepiness Scale was used as the subjective measure of sleepiness.