“…Since Harlow's (1949) introduction of LS, there have been a considerable number of investigations with animals (Harlow, 1959) and children (e.g., Ellis, 1958;Girardeau, 1959;Kaufman & Peterson, 1958;Wischner, Braun, & Patton, 1962). Learning-set studies generally, and particularly those employing children, have utilized for the most part an objectquality problem employing a successive procedure.…”