ABSTRACTGroups of seven and eleven year old children were given a test of visual performance in which they viewed a small white disc on a black background in a tachistoscope and reported whether the disc appeared to disappear when the experimenter switched very briefly to a second completely black field. The shortest disappearance reported was taken as a measure of their dark interval threshold. The threshold decreased with age for girls, who also had a higher threshold than boys at both ages. When the subjects were grouped according to their threshold, the girls at seven and eleven who had a moderate threshold were superior on reading accuracy to those of low and high threshold. For the boys this was so at eleven, but not at seven.