In a method and a device for determining a vigilance state of a motor vehicle driver,a noise signal is generated and a supplementary torque as a function of the noise signal is applied to a steering assembly,a reaction signal of the vehicle driver is determined, andthe vigilance state is determined from a time characteristic of the noise signal and a time characteristic of the reaction signal, at least one parameter of a parameterized transfer function from noise signal to reaction signal is determined, and the vigilance state is determined as a function of an absolute value of the at least one parameter and/or as a function of a relative change of the at least one parameter with regard to at least one earlier parameter, the at least one earlier parameter having been determined at an earlier instant in time.
