A method for processing EEG signals collected during a study period, the method comprising: • reading the EEG signals from two frontal electrodes (101, 102) of an electroencephalograph; wherein the EEG signals are read as a difference between the particular electrode signal and a reference signal suitable to underline differences between the activity beneath the two frontal electrodes (101, 102), • determining values of a BIS/BAS response on the basis of an asymmetry between the EEG signals; characterized by • for a plurality of consecutive time moments within the study period, converting EEG signals from each of the two frontal electrodes (101, 102) within a time window, from a time domain to the frequency domain, in a frequency band from 26 to 29 Hz, to obtain EEG converted signals from each of the two frontal electrodes (101, 102); • for each of the plurality of consecutive time moments, normalizing the amplitude of the EEG converted signal from only the first electrode by calculating an average normalized amplitude of the EEG converted signal from only the first electrode, for the frequency band from 26 to 29 Hz, relative to a normalization time segment; • for each of the plurality of consecutive time moments, normalizing the amplitude of the EEG converted signal from only the second electrode by calculating an average normalized amplitude of the EEG converted signal from only the second electrode, for the frequency band from 26 to 29 Hz, relative to the normalization time segment; • calculating the asymmetry between the EEG signals as a difference between the average normalized amplitude of the EEG converted signal of the first electrode and the average normalized amplitude of the EEG converted signal of the second electrode, for each of the time moments. • reading the EEG signals from two frontal electrodes (101, 102) of an electroencephalograph; wherein the EEG signals are read as a difference between the particular electrode signal and a reference signal suitable to underline differences between the activity beneath the two frontal electrodes (101, 102), • determining values of a BIS/BAS response on the basis of an asymmetry between the EEG signals; • for a plurality of consecutive time moments within the study period, converting EEG signals from each of the two frontal electrodes (101, 102) within a time window, from a time domain to the frequency domain, in a frequency band from 26 to 29 Hz, to obtain EEG converted signals from each of the two frontal electrodes (101, 102); • for each of the plurality of consecutive time moments, normalizing the amplitude of the EEG converted signal from only the first electrode by calculating an average normalized amplitude of the EEG converted signal from only the first electrode, for the frequency band from 26 to 29 Hz, relative to a normalization time segment; • for each of the plurality of consecutive time moments, normalizing the amplitude of the EEG converted signal from only the second electrode by calculating an average normalized amplitude of the EEG converted signal from only the second electrode, for the frequency band from 26 to 29 Hz, relative to the normalization time segment; • calculating the asymmetry between the EEG signals as a difference between the average normalized amplitude of the EEG converted signal of the first electrode and the average normalized amplitude of the EEG converted signal of the second electrode, for each of the time moments.