A system for controlling one or more functions of a vehicle responsive to a cognitive state of a vehicle user comprises one or more controllers configured to receive cognitive state data indicative of a cognitive state of the user of the vehicle and context data indicative of a context of one or both of the user and the vehicle. The one or more controllers are configured to control the one or more functions of the vehicle in dependence on the received indication of the cognitive state of the user and the context data. The controllers are configured to output control data for controlling the one of more functions of the vehicle.