[Assessment of vigilance]

Two aspects of vigilance are to be distinguished: the quantitative one refers to sleep-wakefulness dimension and the qualitative one refers to focusing of attention. Their combination leads to a curvilinear relationship between activation and performances. After describing the psychometric characteristics of vigilance tests, some examples are given of simple paper-pencil or more sophisticated methods. Physiological indices are also approached. The sources of variation influencing vigilance measurement are presented and also some useful experimental designs. At last some remarks are made on statistical exploitation and interpretation of results.