LYON, THOMAS D., and FLAVELL, JOHN H. YOUNG Children's Understanding of "Remember" and "Forget." CHILD DEVELOPMENT, 1994, 65, 1357-1371.3 studies examined young children's understanding that if one "remembers" or "forgot," one must have known at a prior time. In Study 1,4-year-olds but not 3-year-olds understood the prior knowledge component of "forgot"; both groups understood that a character with prior knowledge was "gonna remember." Study 2 controlled for the possibility that good performance on "remember" might be due to a simple association of remembering with knowledge. A significant number of 4-year-olds but not 3-year olds understood that when 2 characters currently knew, the one with prior knowledge remembered, and that when neither character currently knew, the one with prior knowledge forgot.  Study 3 made prior knowledge more salient by making the remembered or forgotten item visible to the subjects throughout. 4-year-olds performed near ceiling on both verbs, whereas 3-year olds' performance did not differ from chance. The results are discussed in relation to children's developing understanding of the mind.