The present invention relates to a neurofeedback system that comprises an electrode (2, 2′, 2″) for contacting skin (6) of a user (7) for measuring a biofeedback signal (9) of the user (7), a first signal processing unit (3) for determining a signal characteristic (11) of the measured biofeedback signal (9), wherein the signal characteristic (11) represents a neurofeedback, a second signal processing unit (4) for determining a biofeedback signal quality (12) of the measured biofeedback signal (9) by extracting a signal feature of the measured biofeedback signal (9) and calculating a probability of a measurement error for said signal feature, which probability represents the biofeedback signal quality (12), and a feedback unit (5) for providing feedback to the user, wherein the feedback comprises the neurofeedback and a feedback about the biofeedback signal quality (12). A further aspect of the invention relates to a method for supporting a behavior change of a person and a computer program for carrying out said method.