A control system of the invention for regulating a quantity to be
controlled based on a deviation of the controlled quantity from a target
value thereof and control parameters includes a behavior feature value
calculator, a basic state judgment data calculator and a control
parameter setter. The behavior feature value calculator detects the
period or frequency of behaviors of a specific kind performed by a
subject to be controlled. The basic state judgment data calculator
calculates the amount of variations in the aforementioned period or
frequency. The control parameter setter updates the value of at least one
of the control parameters based on the amount of the aforementioned
variations.