the invention relates to a method and apparatus for measuring the responsiveness of a subject with lowered level of consciousness . physiological signal data is obtained from the subject and a first measure indicative of the level of consciousness of the subject is derived from the physiological signal data . in order to obtain an objective measure of the responsiveness of the subject and to improve the specificity of patient monitoring , a sequence of the first measure is recorded without inducing arousals in the subject and a second measure indicative of a responsiveness of the subject is determined based on the recorded sequence . the determination of the second measure may be independent of the unintentional stimuli that cause arousals in the patient or the stimuli causing such arousals in the clinical environment may be detected to find out their effect on the first measure .