The present application relates to a communication system for controlling the output of messages to a vehicle occupant. The communication system has a processor configured to output a first message to the vehicle occupant. A signal is received from one or more sensors operative to monitor the vehicle occupant when the first message is output. The signal from said one or more sensors is analysed to determine one or more parameters relating to the response of the vehicle occupant to said first message. The communication system controls the subsequent output of at least said first message in dependence on said one or more determined parameters. The present application also relates to a method and to a vehicle.