This study evaluated how people learn about encoding strategy effectiveness in an associative memory task. Individuals studied two lists of paired associates under instructions to use either a normatively effective strategy (interactive imagery) or a normatively ineffective strategy (rote repetition) for each pair. Questionnaire ratings of imagery effectiveness increased and ratings of repetition effectiveness decreased after task experience, demonstrating new knowledge about strategy effectiveness. Cued recall confidence judgments, measuring confidence in recall accuracy, were almost perfectly correlated with actual recall and strongly correlated with postdictions--estimates of recall for each strategy. A structural regression model revealed that postdictions mediated both changes in second-list predictions and changes in strategy effectiveness ratings, implicating accurate performance estimates based on item-level monitoring as the key to updating strategy knowledge. (Contains 5 tables and 3 figures.)