The Generation Effect in

ABSTRACT— Howwelloneretainsnewinformationdependson how actively it is processed during learning. Active at-temptstoretrieveinformationfrommemoryresultinmorelearningthanpassiveobservationofthesameinformation(the generation effect). Here, we present evidence for thegeneration effect in monkeys. Subjects were trained torespond to ﬁve-item lists of photographs in a particularorder. On some lists, they could request ‘‘hints’’ to guidetheirbehavior;onothers,theyhadto generate thecorrectorder from memory. Training with hints resulted in highlevels of initial performance, but accuracy dropped pre-cipitously when the hints were removed on the criteriontest. Training without hints led to relatively poor initialperformance, but accuracy increased steadily and re-mained high on the criterion test.Psychologists have pondered the importance of how informationisprocessedformorethanacentury.James(1890)remarked,‘‘Acurious peculiarity of our memory is that things are impressedbetter by active than by passive repetition’’ (p. 646, italicsadded). The generation effect refers to the fact that active re-trieval of information from memoryresultsin more learningthanpassive observationofthesame information(HirshmanB Jacoby, 1978; Slamecka & Graf, 1978). The generationeffect is closely related to the testing effect—that is, the ﬁndingthattakingtestsduringlearningenhanceslong-termretentionofinformation (Carrier & Pashler, 1992; Glover, 1989; Hogan K Roediger & Karpicke, 2006a, 2006b). The generation effect was discovered in experiments withhuman subjects who were trained in various verbal learningparadigms. In the present study, we asked whether an advantageof active learning is a fundamental principle of memory that canbe studied in nonverbal animals. To address this question, weassessed the degree to which active processing affected seriallearning in 2 rhesus macaque monkeys. Both subjects hadextensive experience learning simultaneous chains, lists ofarbitrarilyselecteditems (usuallyphotographs)displayedsimul-taneously on a touch-sensitive video monitor, in a different con-ﬁguration on each trial (Terrace, Son, & Brannon, 2003). Thesubjects’ task was to touch the items in a particular order, irre-spectiveof theirpositionsonthemonitor. Eachnewlisthadtobelearned by trial and error. Food reinforcement was provided onlyafter the subject responded correctly to all of the list items. Anerror, at any position in the list, terminated the trial with a time-out.Both subjects also had prior training in which a ‘‘hint’’ optionwas added to the simultaneous-chaining paradigm (Kornell,Son, & Terrace, 2007). Touching the hint icon caused a blinkingborder to appear around the list item to be selected next. Sub-jects learned to request hints. More important, the frequencywith which they requested hints decreased as their accuracyincreased.Thatrelationshipsuggestedthatsubjectswereabletomonitor their accuracy and request hints only when they wereunsure about which item they should select next.In the current experiment, each subject was trained on newﬁve-item lists under four conditions. Under the ﬁrst, the hinticonwasnotdisplayed,buthintswereprovidedautomaticallyonevery trial. Under the second, subjects could obtain a hint onevery trial by touching the hint icon. Under the third, they couldobtainahinton50%ofthetrials;ontheother50%,thehinticonwas not presented. Hints were never available under the fourthcondition.To assess the extent to which hints facilitated (or inhibited)learning during the ﬁrst 3 days of training, we tested all sub-jects on the 4th day, without hints. If hints facilitated accu-racy during training, and if a high level of accuracy duringtraining indicates a high level of list learning, accuracy onthis test would be expected to be higher on lists trainedwith hints than on lists trained without hints. Conversely,if the effort of generating correct responses is more effectivethan using a hint, accuracy on this test would be expected to behigher on lists trained without hints than on lists trained withhints.