Can you tell if these faces are real or GAN-generated?

Hi HN! We are a pair of students at MIT trying to measure how well humans can differentiate between real and (current state-of-the-art) GAN-generated faces, for a class project. We're concerned with GAN images' potential for fake news / ads, and we believe it would be good to know, empirically, how often people get fooled under different image exposure times.