Anomaly in coupled parametric resonance

We present experimental observations of an anomaly in the coupled response of auto-parametrically excited microelectromechanical beams. When one of the two coupled beams is driven at elevated amplitudes, the excitation of dominant and recessive modes is observed in the driven and non-driven beams respectively. This anomalous nature of auto-parametric excitation has been unexplored by both theory and experiments and falls outside the scope of the conventional description of parametric resonance.