By applying a staggered driving force in a prototypical discrete
model with a quartic nonlinearity, we demonstrate the spontaneous
formation and destruction of discrete breathers with a selected
frequency due to thermal fluctuations. The phenomenon exhibits the
striking features of stochastic resonance: a nonmonotonic behavior as
noise is increased and breather generation under subthreshold
conditions. The corresponding peak is associated with a matching
between the external driving frequency and the breather frequency at
the average energy given by ambient temperature.