“…We considered ensemble made up of 3 multi-modal experts (i.e., different biometric traits and different algorithms). In the case of the NIST dataset we used all the possible combinations of experts, while in the case of the FVC2004 datasets we sorted all the possible ensembles according to the value of the d , that is a measure of the separation of the distributions of positive and negative score, the larger the d , the higher the separation [9]. Then, we selected the 10 pairs with the largest value of d , and the 10 pairs with the smallest value of d .…”