The objective of the invention is a method and a device for identifying, measuring and analyzing abnormal neurological responses. In the method in accordance with the invention neurological diseases, pain, fatigue, power producing ability and/or activeness and/or symptoms connected with those are estimated by measuring signals produced by muscles and by analyzing signals with nonlinear calculation methods. The device in accordance with the invention includes sensors to be placed in the body or on the body surface for measuring signals produced by muscles, a signal-analyzing device for analyzing signals with nonlinear calculation methods and a feedback device for giving feedback.