... mother when she was staring straight into the eyes of the experimenter. Any psychologist, on the contrary, would say that that would be a most favourable condition for watching small signs. He knows that while we fixate a point with the centre of our eye we are most sensitive to slight movement impressions on the side parts of our eye, and that this sensitiveness is often abnormally heightened. Just when the child is looking steadily into our face or to the ceiling, the outside parts of her sensitive retina ... — Psychology and Social Sanity • Hugo Muensterberg