“…His results showed the following: (1) by comparing the neutral faces and FE, the average genuine similarity has been degraded; (2) sadness and disgust expressions are the most dissimilar expressions among the other expressions; (3) the best class to be verified with was the normal face, as there was no facial deformation and muscle movement; (4) For users who enrolled with happy, angry, surprised, disgusted, sad, and fearful expressions, thebest expressions to verify with are fearful, sad, fearful, sad, fearful expressions, respectively; (5) the lowest matching score was achieved when users who provided happy, angry, surprised, disgusted, sad, fearful faces during the enrollment, identified themselves with disgusted, surprised, angry, happy, angry faces respectively during the verification. Another study investigated the effect of FE on FB systems by Márquez-Olivera et al [37], where they analyzed their FB system under the influence of FE. It has been concluded that failures occurred when the subjects expressed surprise as it has maximum facial deformations while the sadness and anger expressions express high deformation on eye regions.…”