A method of discriminating the state of an object on a vehicle seat. The method includes taking samples of a signal indicative of seat load. It is provisionally determined that the object is in a second state if the seat load exceeds a first threshold, and it is provisionally determined that the object is in a first state if the seat load is less than a second threshold. It is determined that the object is in the first state if it is provisionally determined that the object is in the first state and if it is not provisionally determined that the object is in the second state. It is determined that the object is in the second state if it is provisionally determined that the object is in the second state and if it is not provisionally determined that the object is in the first state.