  Using the input energy per cycle as a quantifier of stochastic resonance
(SR), we show that SR is observed in superharmonic (hard) potentials. However,
it is not observed in subharmonic (soft) potentials, even though the potential
is bistable. These results are consistent with recent observations based on
amplitude of average position as a quantifier. In both soft and hard
potentials, we observe resonance phenomenon as a function of the driving
frequency. The nature of probability distributions of average work are
qualitatively different for soft and hard potentials.
