A vehicle occupant sensing system that includes a sensor assembly. The sensor assembly has a housing that includes a base and an upper slide member. The upper slide member is moveable toward and away from the base. A sensor is operatively fixed relative to at least one of the upper slide member and the base and is operable to detect movement of the upper slide member toward and away from the base. Additionally, the vehicle occupant sensing system includes a variable biasing member adapted to bias the upper slide member away from the base with a force that is non-linearly related to movement of the upper slide member toward and away from the base. The vehicle occupant sensing system of the present invention may be employed in a vehicle seat assembly to detect a condition of the vehicle seat assembly.