A vehicle seat is disclosed with a seatback frame for supporting the back of an occupant. A head restraint extends from the seatback frame for supporting the head of the occupant. In one embodiment, a four-bar mechanism is operably connected to the seatback frame and the head restraint for receiving an input force from the occupant in response to an impact condition, and for consequently actuating the head restraint to an actuated position. In another embodiment, the four-bar mechanism locks the head restraint in the actuated position in response to an input force of the occupant resting against the seatback.