The headrest (10) has an outer shell (12) which is coupled with a seat (100) in a movable manner and defines an inner space (14) and a position relative to the seat. A mechanical linkage system (18) is fixed at the shell or the seat. An actuator (16) is arranged in the space, where the actuator has an element made of an active material. A power source is coupled and operated with the actuator, in order to generate the signal.