Abstract: A system and method for determining a peak performance state by coherency of input signals from a test subject. The system includes two sensors for receiving separate input signals from a test subject. The system also includes a processor that is in communication with the sensors. The system further includes a memory that stores baseline data and is connected to the processor. The method includes the steps of receiving input signals from two sensors, communicating the input signals to a processor, analyzing the input signals with the processor as a function of a nonlinear relationship to determine coherency, and comparing the coherency data to baseline data stored in the memory to determine the presence of a peak performance state.