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Costs and Benefits in ItemMethod Directed Forgetting: Differential Effects of Encoding and Retrieval Yuh-Shiow Lee
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National Chung-Cheng University Published online: 14 Jun 2013.
To cite this article: Yuh-Shiow Lee (2013) Costs and Benefits in Item-Method Directed Forgetting: Differential Effects of Encoding and Retrieval, The Journal of General Psychology, 140:3, 159-173, DOI: 10.1080/00221309.2012.750591 To link to this article: http://dx.doi.org/10.1080/00221309.2012.750591
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The Journal of General Psychology, 2013, 140(3), 159–173 C 2013 Taylor & Francis Group, LLC Copyright
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Costs and Benefits in Item-Method Directed Forgetting: Differential Effects of Encoding and Retrieval YUH-SHIOW LEE National Chung-Cheng University
ABSTRACT. This study examined how encoding and retrieval factors affected directed forgetting costs and benefits in an item-method procedure. Experiment 1 used a typical item-method procedure and revealed a levels-of-processing effect in overall recall. However, the deep encoding condition showed a smaller directed forgetting effect than the shallow encoding conditions. More importantly, “remember” (R) words were selectively rehearsed as indicated by greater recall from the primacy portion of the list and more apt to be recalled before “forget” (F) words. Experiment 2 showed that a deep encoding operation reduced directed forgetting costs and that directed forgetting benefits occurred only when R words were recalled before F words. These findings supported the hypotheses that encoding manipulation affected directed forgetting costs and that directed forgetting benefits were associated with output order bias. Results were discussed in terms of mechanisms that produce item-method directed forgetting. Keywords: levels-of-processing, output order, selective rehearsal, serial position curve
ONE OF THE METHODS USED TO EXAMINE INTENTIONAL forgetting is the directed forgetting paradigm. This paradigm includes two procedures to present instructional cues to participants regarding items they should forget or remember. In the item-method directed forgetting procedure, participants are given explicit cues for each to be forgotten (F) word, such as “forget,” and for each to be remembered (R) word, such as “remember.” The memory cue is typically presented after the relevant item to ensure that the participant has registered the study item and that each item receives the same amount of initial encoding. The The author would like to thank an anonymous reviewer for the suggestion and idea for conducting Experiment 2. This research was supported by Research Grant NSC-99-2410H-194-039-MY3 from the National Science Council of the Republic of China. Portions of this research were presented at the Association for Psychological Science 23rd Annual Convention, Washington, DC, USA. Address correspondence to Yuh-shiow Lee, Department of Psychology, National ChungCheng University, Chiayi 621, Taiwan, R. O. C.; [email protected] (e-mail). 159
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list method involves only one memory cue that is given in the middle of the list, usually an instruction to forget all of the preceding items. Studies using both procedures have demonstrated impaired memory for forget instructed relative to remember instructed items (see MacLeod, 1998, for a review). The difference in memory retention between F and R words is referred to as the directed forgetting effect. In the item-method procedure, both recognition and recall of F words are found to be impaired relative to R words (Basden & Basden, 1998; Basden, Basden, & Gargano, 1993; MacLeod, 1999; Wilson & Kipp, 1998). In recognition tests using the remember-know paradigm, participants made more “remember” responses for R words than for F words, but made a similar number of “know” responses regardless of the associated memory instruction (e.g., Gardiner, Gawlik & Richardson-Klavehn, 1994). Moreover, memory is impaired for F words on certain implicit memory tests, such as word-fragment and word-stem completion (MacLeod, 1989). The time and resources available for post-cue encoding had a larger effect on R than on F words (e.g., Davis & Okada, 1971; Macleod, 1989; Wetzel & Hunt, 1977). Based on these findings, several studies suggest that the item method, which differs from the list method, promotes selective rehearsal favoring the R words (Basden & Basden, 1998; Basden, Basden & Gargano, 1993; MacLeod 1999; Wilson & Kipp, 1998). This selective rehearsal account has been the major theory of item-method directed forgetting for decades (e.g., Bjork, 1972; MacLeod, 1975; Wetzel, 1975). Most studies on item-method directed forgetting compare F and R word retention within the same group of participants (the “remember-forget” group), who were asked to remember and forget certain words. In typical results of the item-method directed forgetting experiment, memory retention is better for R words than for F words because of worsened performance (costs) for F words and improved performance (benefits) for R words. Thus, the directed forgetting effect estimated from a single group of participants actually includes both directed forgetting costs and benefits. A directed forgetting cost is memory impairment for F words, whereas a directed forgetting benefit is memory gain for R words, as a result of the forget instruction. To separate directed forgetting costs and benefits, a control group (the “remember-all” group) receiving only “remember” cues is required. The control group provides a baseline for estimating memory improvement for R words and memory decline for F words in the “remember-forget group.” Directed forgetting costs can be estimated based on the difference in F word (the “remember-all” group actually has to remember these words) retention between the “remember-forget” and the “remember-all” groups. Directed forgetting benefits can be estimated from the difference in R word retention between these two groups. In item-method directed forgetting, all items receive maintenance rehearsal before the cue to remember or forget appears (Woodward, Bjork, & Jongeward, 1973). According to the selective rehearsal account, R word rehearsal continues and becomes elaborated, whereas F words do not receive such elaboration after
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cue presentation. As a result, R words retain a stronger, recollective memory trace relative to F words. The “remember-all” group, however, would try to rehearse all the study words. Thus, the directed forgetting costs presumably come from the difference in F word rehearsal during encoding between the “remember-forget” and the “remember-all” groups. The “remember-forget” group would stop to process F words (e.g., Lee, Lee, & Fawcett, in press) after the forget memory cue appears. If this is the case, then directed forgetting costs should also be affected by other types of levels-of-processing manipulations. During memory retrieval (e.g., a free recall test), the “remember-forget” group would be biased to recall R words prior to F words, because R words are better encoded and more accessible than F words, whereas the “remember-all” group would not show this kind of output order bias; all the study words would have the same chance to be retrieved. As a result, when retrieving R words, the “remember-all” group would experience greater output interference than the “remember-forget” group. In other words, the directed forgetting benefits for R words would come from the difference in output interference between the “remember-forget” and the “remember-all” groups. If this is the case, then an output order manipulation should affect directed forgetting benefits. Directed forgetting benefits should occur only when R words are recalled before F words. The two experiments reported in this study were designed to test the above hypotheses regarding the origins of directed forgetting costs and benefits in itemmethod directed forgetting. In this paradigm, previous studies suggest that R words are better remembered than F words because R words have benefited from more rehearsal following initial encoding. This differential rehearsal would have less or no effects on study words that have been processed deeply. For a deeply encoded F word, an instruction to forget should have a limited effect on retention, as compared with a shallowly encoded F word (see MacLeod & Daniels, 2000; Houriham & MacLeod, 2008). This limitation would reduce the directed forgetting costs because it decreases encoding differences of F words between the “rememberforget” and the “remember-all” groups. Furthermore, if the directed forgetting benefits for R words, as mentioned above, come from reduced output interference for the “remember-forget” group, then it should appear only when R words are recalled before F words and should be reduced or diminished when F words are recalled before R words. Several previous studies examined the levels-of-processing effect on itemmethod directed forgetting. However, the results were mixed. They suggest either no difference in the directed forgetting effect between the shallow and deep processing conditions (Dulaney, Marks, & Link, 2004; although in Experiment 1, the directed forgetting effect from the recognition test was reduced in the deep encoding condition) or that the deep processing condition had a smaller directed forgetting effect than the shallow processing condition (Wetzel, 1975; Geiselman, Rabow, Wachtel, & MacKinnon, 1985). One study found a larger directed forgetting effect in the deep processing condition (Horton & Petruk, 1980). The results
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of Horton and Petruk (1980) may have been due to their unusual manipulations of list categorical structures and timing of the levels-of-processing tasks. The purpose of Experiment 1 was to use a typical item-method procedure and a standard levels-of-processing manipulation to examine this possibility. More importantly, before directly testing the above hypotheses regarding directed forgetting benefits and costs, it is important to provide more direct evidence for the notion that in a typical item-method procedure participants selectively rehearse R words, but not F words and tend to recall R words before F words in a free recall test. The selective rehearsal account is often inferred from the result that R words were recalled and recognized better than F words. To provide direct evidence for the selective rehearsal of R words, Experiment 1 compared R word and F word recall under serial position analyses focusing on the primacy region and recency region of the serial position curve. Previous studies have suggested that the primacy effect is due to the tendency to rehearse the first few study words (Rundus, 1971; Tan & Ward, 2000). The selective rehearsal account predicts that the recall difference between R words and F words should mainly come from the primacy region of the cure. Experiment 2 directly tested the proposed hypotheses by manipulating both the encoding operation and recall order to examine their effects on directed forgetting costs and benefits. Experiment 1 Experiment 1 had two purposes. First, this experiment examined the levels-ofprocessing manipulation on item-method directed forgetting. Second, this experiment tried to provide more direct evidence that, in a typical item-method directed forgetting involving free recall, participants would rehearse R words but not F words, and would tend to recall R words before F words. Method Participants and Design All the participants in this study were native Chinese speakers. To partially fulfill course requirements, 28 university students taking introductory psychology courses participated voluntarily. This experiment was a 2 by 2 within-subjects design. The two independent variables were the encoding operation (shallow vs. deep processing) and memory cue (remember vs. forget) following each study word. Materials Forty two-character Chinese words from different categories were selected. All the words were high frequency concrete nouns. They were divided into two
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sets of twenty words and assigned “forget” and “remember” cue conditions. Furthermore, one-half of the words in each set were paired with the processing cue word “” (stroke) and the other half were given the processing cue word “ ” (good-bad). The assignment of each set was counterbalanced, so that each word had an equal chance to receive “forget” and “remember” cues and to be paired with “stroke” or “good-bad” processing cues. The experiment was run on a personal computer. The viewing distance was 50 cm and the character size was 3 cm × 3.5 cm. Procedure Participants were tested individually. Each experimental session consisted of a study phase and a testing phase. During the study phase, participants studied the forty words one by one. A processing cue word, “” (stroke) or “” (goodbad), appeared below each study word. For each study word, participants had to judge which of the two characters of the study word had more strokes when the processing cue word “stroke” appeared. They also had to judge whether the study word had a good or bad connotation when the cue word “good-bad” appeared. Participants responded orally by saying “left (or right)” or “good (or bad)”. After studying each word for five seconds, participants were given a cue to remember or forget the study word. The cue remained on the screen for 2.5 seconds. The next study word and processing cue appeared after a 0.5-second blank screen. The presentation order of the study words and cue words was randomly determined. However, the same type of cue word, either a processing cue or memory cue word, would not appear for more than three consecutive trials. Participants performed a free recall test after studying all the words. They were instructed to recall in any order as many of the study words as possible, regardless of whether they were “forget” words or “remember” words and write down their answers on a piece of paper. After the experiment was over, participants were instructed not to discuss the experiment with other potential participants. Results The following analyses are based on the correct recall rate focusing separately on the serial position curve and the recall order. Serial Position Analyses For each position n, the serial position curve was smoothed by averaging original data, with the exception of the first and the last positions of the curve, from three adjacent points, Xs (n) = [X(n – 1) + X(n) + X(n − 1)]/3. The first and the last positions were averaged based on two adjacent points, Xs(1) = [X(1) + X(2)]/2 and Xs(last) = [X(last − 1) + X(last)]/2. Figure 1 shows the results. To
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FIGURE 1. Serial position curve for remember and forget word recall as a function of encoding operation and position.
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TABLE 1. Mean Rates of Correct Free Recall as a Function of Encoding Operation and Memory Cue (Standard Errors in Parentheses) in Experiment 1
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Deep processing Shallow processing
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examine the serial position effect, the analyses first combined positions 1 to 3 (primacy), positions 4 to 7 (middle) and position 8 to 10 (recency). A 2 (encoding operation: deep vs. shallow) by 2 (memory cue: forget vs. remember cue) by 3 (position: primacy vs. middle vs. recency) ANOVA was then performed. The analyses showed significant main effects of encoding operation, memory cue, and serial position [F(1, 27) = 14.68, MSe = .08, p < .001, η2p = .35; F(1, 27) = 112.94, MSe = .09, p < .001, η2p = .81; and F(2, 54) = 4.19, MSe = .04, p < .05, η2p = .13, respectively]. More importantly, the interaction effect between memory cue and position was also significant [F (2, 54) = 14.07, MSe = .04, p < .001, η2p = .33]. The interaction effect between encoding operation and memory cue was marginally significant [F (1, 27) = 3.80, MSe = .07, p < .062, η2p = .12]. No other reliable interaction effects were found (all F’s < 1). Post-hoc tests showed that R words in the primacy region were recalled better than both the middle and recency regions (M = .69 vs. M = .59 and M = .60; both p’s < .05). F words in the recency region were recalled better than both the primacy and middle regions (M = .40 vs. M = .20 and M = .25; both p’s < .001). These results indicated that R words showed a primacy effect, whereas F words only revealed a recency effect. As for the interaction between encoding operation and memory cue (see Table 1), post-hoc tests revealed that both the shallow processing and deep processing conditions showed significant directed forgetting effects (Mdf = .39 and Mdf = .28; both p’s < .001). The F words showed a significant levels-of-processing effect (Mlop = .16; p < .01), whereas R words did not (Mlop = .06; p = .48). Analyses of Recall Order Correlations were calculated on the serial position of each word on the recall list and the type of words to examine whether participants were more apt to recall R words before F words and deeply processed words before shallowly processed words. Dummy codes were used to index that R words and deeply processed words (e.g., coded as “1”) were recalled before F words and shallowly
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processed words (e.g., coded as “2”). Thus, a positive correlation indicated that R words were recalled on the average earlier in output than F words and deeply processed words were recalled earlier than shallowly processed words. Across all the participants the correlation between serial position and whether a word was followed by an F or R memory cue was significant [r = .29, t(476) = 6.52, p < .001], whereas the correlation between serial position and whether a word was deeply or shallowly processed was not significant [r = −.08, t(476) = − 1.66, p = .11]. Furthermore, 23 out of 28 (82%) participants began their recall with an R word, 21 out of 28 (75%) participants started their recall with two R words, and 17 out of 28 (61%) participants started their recall with three R words. These results suggest that participants tended to recall R words before F words in the free recall test. Discussion This experiment found a typical levels-of-processing effect for the F words and not the R words. Furthermore, the shallowly processed words revealed a larger directed forgetting effect than the deeply processed words. Consistent with the proposed hypothesis, for the deeply processed words, because initial encoding has optimized memory performance, the normal effect of the “forget” instruction was reduced. Experiment 1 also demonstrated that, in a typical item-method directed forgetting paradigm involving free recall, R words were recalled before F words during retrieval. The directed forgetting effect in this experiment, estimated by comparing R word and F word recall within a group, presumably came from two different sources. First, according to the serial position analyses, R words, but not F words, showed a primacy effect suggesting that participants selectively rehearsed R words. As indicated by the recency effect, the rate of F word recall was mainly determined by the decay of memory strength over time; later presented items were remembered better than those presented earlier. There was little evidence to suggest that participants rehearsed F words, either intentionally or accidentally. Second, recall order analyses indicated that in the free recall test, participants tended to recall R words before F words, regardless of types of encoding operation. The bias in recall order should have also contributed to the directed forgetting effect. Experiment 2, including a “remember-all” control group, was designed to test directly the hypothesis that selective rehearsal and output bias are associated with different sources of the directed forgetting effect. Experiment 2 Experiment 2 aims to test the hypothesis that directed forgetting costs and benefits in the item-method are associated with different mnemonic factors involving either encoding or retrieval processes. This experiment manipulated both
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the encoding operation and recall order. The encoding manipulation was the same as that of Experiment 1. However, participants in Experiment 2 had to perform a cued recall, instead of a free recall test. During testing, a categorical cue was given to the participants to control recall order. A control group who only received the “remember” cue was included to estimate directed forgetting costs and benefits. Method Participants and Design Sixty-four university students taking introductory psychology courses voluntarily participated to fulfill course requirements. This experiment was a 2 by 2 by 2 by 2 mixed design. Encoding operation (shallow vs. deep processing) and memory cue (remember vs. forget) following each study item were the withinsubjects factors. The between-subjects factors were recall order (R word first vs. F word first) and memory group (remember-forgetting vs. remember-all group). There were 16 participants in each of the 4 between-subjects combinations of conditions. Materials The study materials were the same forty two-character Chinese words used in Experiment 1. They belonged to different taxonomic categories and forty categorical names were used as retrieval cues during the final memory test. Procedure The procedures were the same as those of Experiment 1, with two exceptions. First, during the final recall test, participants had to perform a cue recall, instead of a free recall test. Participants were asked to recall the study words when a categorical name appeared in the center of a computer screen. The recall order, determined by the retrieval cue, was manipulated between participants. Half of the participants recalled “remember” words before “forget” words. The other group of participants recalled “forget” words before “remember” words. The categorical names were presented randomly within each type of memory cue. The random sequence was different for each participant. Second, a control (“remember-all”) group was included. The remember-all and experimental (“remember-forget”) groups were yoked; each participant in the remember-all group was assigned for each participant in the remember-forget group. The remember-all group of participants followed an identical procedure and design as the remember-forget group, except that during the study phase all the “forget” cues were replaced by the
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“remember” cues. Thus, the remember-all group only received the “remember” cues. Participants were told that the “remember” cue was used to remind them to remember each study words. Participants were instructed not to discuss the experiment with other potential participants after the experiment was over.
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Results Table 2 presents the mean rates of correct recall. The only difference between the “remember-all” and “remember-forget” groups was that, for the “rememberall” group, the “remember” cue replaced the “forget” cue. The recall rate of the remember-all group was analyzed in the same manner as the remember-forget group. F words for the remember-all group were actually the study words that they were asked to remember. A 2 (encoding operation: deep vs. shallow) by 2 (memory cue: forget vs. remember cue) by 2 (memory group: remember-forgetting vs. remember-all group) by 2 (recall order: R word first vs. F word first) ANOVA was performed. Both main effects of encoding operation and memory cue were significant [F (1, 60) = 60.25, MSe = .02, p < .001, η2p = .50; and F (1, 60) = 26.63, MSe = .03, p < .001, η2p = .31, respectively.] The interactions between memory cue and memory group and between encoding operation and memory cue were also significant [F (1, 60) = 17.48, MSe = .03, p < .001, η2p = .23; and F (1, 60) = 4.18, MSe = .02, p < .05, η2p = .07, respectively.] The three-way interaction between encoding operation, memory cue, and memory group was significant [F (1, 60) = 8.25, MSe = .02, p < .01, η2p = .12.] All other effects were not reliable (all p > .12). The inclusion of the remember-all group enabled the present study to estimate
TABLE 2. Mean Rates of Correct Cued Recall as a Function of Group, Memory Cue, Encoding Operation, and Recall Order (Standard Errors in Parentheses) in Experiment 2 Remember-forget group F word Recall order R – F order F – R order
.65 (.04) .72 (.05)
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Deep processing .84 (.02) .67 (.05) .77 (.03) .73 (.04) Shallow processing .77 (.02) .56 (.05) .71 (.05) .66 (.05)
R word .72 (.04) .75 (.04) .55 (.07) .68 (.04)
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separately the directed forgetting benefits and costs. In the following these two effects were analyzed separately.
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Directed Forgetting Benefits For R Words As mentioned above, the directed forgetting benefit refers to the differences in the recall of R words between the “remember-all” and “remember-forget” groups. A 2 (encoding operation: deep vs. shallow processing) by 2 (group: “rememberall” vs. “remember-forget” group) by 2 (recall order: R word first vs. F word first) ANOVA was performed on the recall of R words. The main effects of both encoding operation and group were significant [F(1, 60) = 22.77, MSe = .01, p < .001, η2p = .28 and F(1, 60) = 6.96, MSe = .04, p < .05, η2p = .10, respectively.] R words in the deep processing condition were recalled more than those in the shallow processing condition were (M = .68 vs. M = .53). The interaction between group and recall order was also significant [F(1, 60) = 3.96, MSe = .04, p < .052, η2p = .06.] Post hoc tests showed that when R words were recalled before F words, the “remember-forget” group recalled more R words than the “rememberall” group (M = .80 vs. M = .64; p < .01). There was no difference between “remember-forget” and “remember-all” groups (M = .74 vs. M = .72) when F words were recalled before R words (the F-R order). These results indicate that directed forgetting benefits occurred only when participants recalled in the R-F order. Directed Forgetting Costs For F Words The directed forgetting cost refers to the differences in the recall of F words between the “remember-all” and “remember-forget” groups. To analyze directed forgetting costs, a 2 (encoding operation: deep vs. shallow processing) by 2 (group: remember-all vs. remember-forget group) by 2 (recall order: R word first vs. F word first) ANOVA was performed on F word recall. The main effects of encoding operation and group were significant [F(1, 60) = 37.36, MSe = .02, p < .001, η2p = .38 and F(1, 60) = 5.97, MSe = .04, p < .05, η2p = .09, respectively.] More importantly, there was a significant interaction between group and encoding operation [F(1, 60) = 7.12, MSe = .02, p < .01, η2p = .11.] Post hoc tests showed that the difference in recall of F words between “remember-forget” and “remember-all” groups was found in the shallow processing condition (M = .44 vs. M = .61; p < .01), and not in the deep processing condition (M = .68 vs. M = .70). Apparently, only the shallow processing condition produced directed forgetting costs. Discussion In this experiment, the output order was controlled and directed forgetting costs for F words and benefits for R words were estimated separately by including
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a control (remember-all) group that was required to remember all the study words. The results provided clear evidence that directed forgetting benefits for R words occurred only when participants recalled R words before F words. In addition, only the shallow processing condition produced directed forgetting costs for F words. These results are consistent with the current hypotheses. First, encoding operation is associated with directed forgetting costs for F words because as compared with the shallowly processed F words, the deeply processed F words were better (deeply) encoded and thus less sensitive to the forgetting cue. In addition, directed forgetting benefits for R words come from a difference in the recall order between R words and F words because, as compared with the R-F recall order, the F-R recall order reduced the benefits of R word recall in the remember-forget group. General Discussion The inclusion of a control group that was asked to remember all the study words allowed the current study to separately estimate directed forgetting costs for F words and benefits for R words. The results revealed that directed forgetting costs were related to the encoding operation. The deeply processed F words were less sensitive to the forgetting cue. As a result, directed forgetting costs in the deep processing condition were reduced as indicated by the comparison of F word retention between the “remember-forget” and control (“remember-all”) groups. Furthermore, directed forgetting benefits for R words were sensitive to recall order. When output order was directly manipulated, directed forgetting benefits were found only when R words were recalled before F words. These findings are consistent with the proposed hypotheses that directed forgetting costs for F words come from encoding and directed forgetting benefits for R words are related to retrieval factors. Several previous studies examined the effect of levels-of-processing manipulations on item-method directed forgetting (Dulaney, Marks, & Link, 2004; Geiselman et al., 1985; Horton & Petruk, 1980; Wetzel, 1975). However, they showed inconsistent results. Other studies examined effects similar to that from the levelsof-processing manipulation. MacLeod and Daniels (2000) report that the cue to forget affected “read” words but not “generated” words in free recall. In addition, participants were more apt to intentionally forget verbally encoded items than the self-perform action (Earles & Kersten, 2002). Similarly, an encoding operation that creates the production effect was not susceptible to the instruction to forget (Houriham & MacLeod, 2008). These findings suggest that strong item-specific and distinctive processing from encoding operation such as production or generation overrode the effect of forget memory instruction. In other words, a directed forgetting instruction cannot influence words that have been encoded distinctively. None of the above studies separated costs and benefits of directed forgetting or controlled order of recall. An analysis that includes only the “remember-forget” group and combines the two recall orders was carried out to directly compare
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the current result of Experiment 2 with those from previous studies. The results showed significant main effects of both encoding operation and memory cue, F(1, 31) = 46.42, MSe = .02, p < .001, η2p = .58; and F(1, 31) = 51.04, MSe = .03, p < .001, η2p = .62, respectively. The interaction effect was also reliable, F(1, 31) = 16.52, MSe = .01, p < .001, η2p = .35. The directed forgetting effect, the difference between R and F word recall within the same group of participants, was found for both the shallow (M = .74 vs. M = .44) and deep conditions (M = .81 vs. M = .68). The deep condition nonetheless revealed a smaller directed forgetting effect than the shallow condition. This result was similar to that of Experiment 1 in which directed forgetting benefits and costs were not separated. The directed forgetting effect found in both Experiments 1 and 2 was reduced, but not eliminated as that found in previous studies (Earles & Kersten, 2002; Houriham & MacLeod, 2008; MacLeod & Daniels, 2000). Participants in the present study were asked to make a semantic judgment in the deep encoding condition. This type of semantic encoding seems not as distinctive as that from production and generation which involve strong item-specific processing. Thus, the forget memory instruction still had some effects on memory performance. However, the directed forgetting cost was eliminated for the deeply processed words in Experiment 2 when the directed forgetting costs and benefits were separated. Since the directed forgetting cost was eliminated, the small directed forgetting effect for the deeply processed words found in both Experiments 1 and 2 should mainly come from the R-F recall order (the directed forgetting benefits). When F words were very well-remembered as a result of distinctive processing (e.g., Earles & Kersten, 2002; Houriham & MacLeod, 2008; MacLeod & Daniels, 2000), it was very likely that even the R-F recall order would not produce a directed forgetting (benefit) effect. In Experiment 1, the directed forgetting effect was large (.39) for the shallowly processed words for which participants had to judge which of the two characters of the study word had more strokes. This was essentially a structural complexity judgment. The study words in this condition were very shallowly processed, as indicated by the low recall rate (less than .20) for the first half of F words in the serial position (see Figure 1). Most of the recalled F words came from the last four words in the study list which was presumably still held in short-term memory at the time of the memory test. The shallowly processed R words had the benefit of rehearsal, whereas the shallowly processed F words suffered from lack of rehearsal, shallow encoding and output later than R words. Thus, the present study observed a large directed forgetting effect for the shallow processing condition in a free recall test. The cue recall test, used in Experiment 2 to control the recall order, is different from the free recall test used in most of the directed forgetting experiments. It is useful to compare results from these two procedures. The deeply processed F words benefitted more from cued recall (from .36 in free recall to .69 in cued recall) than the shallowly processed F words did (from .19 to .45). In other words,
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the improvement from free recall to cued recall was more obvious for the deeply processed F words. Thus, given that in both free recall and cued recall R words showed a small levels-of-processing effect, the magnitude of directed forgetting effect in Experiment 2 was significantly reduced (from .28 in Experiment 1 to .12 in Experiment 2) for the deep processing condition, relative to the shallow processing condition (from .38 in Experiment 1 to .30 in Experiment 2). This finding that a retrieval cue facilitated retrieval of the deeply processed F words more than the shallowly processed F words further confirms the effective levels-of-processing manipulation during encoding in the present study. To my knowledge, the present study is the first to demonstrate a dissociation between the effects of directed forgetting costs and benefits in an item-method directed forgetting paradigm and their differential associations with encoding and retrieval factors. Most of the studies attribute the item-method directed forgetting effect to encoding difference between R and F words; however, the magnitude of this effect is inflated by the R-F recall order. A similar result that directed forgetting occurred only when R words were recalled before F words has also been found using the list-method procedure (Golding & Gottlob, 2005). Therefore, controlling recall order should be an important methodological consideration for studies using the item-method procedure. Moreover, the analyses of directed forgetting costs and benefits in the item-method, just as in the list-method -method can provide useful information in understanding specific mechanisms that create this type of intentional forgetting. AUTHOR NOTE Yuh-shiow Lee is a Professor at National Chung-Cheng University, Taiwan, R.O.C. She earned her doctorate at Stony Brook University. Her research is focused on human learning and memory.
REFERENCES Basden, B. H., & Basden, D. R. (1998). Directed forgetting: A contrast of methods and interpretations. In J. M. Golding & C. M. MacLeod (Eds.), Intentional forgetting: Interdisciplinary approaches (pp. 139–172). Mahwah, NJ: Erlbaum. Basden, B. H., Basden, D. R., & Gargano, G. J. (1993). Directed forgetting in implicit and explicit memory tests: A comparison of methods. Journal of Experimental Psychology: Learning, Memory, & Cognition, 19, 603–616. Bjork, R. A. (1972). Theoretical implications of directed forgetting. In A. W. Melton & E. Martin (Eds.), Coding processes in human memory (pp. 217–235). Washington, DC: Winston. Davis, J. C., & Okada, R. (1971). Recognition and recall of positively forgotten items. Journal of Experimental Psychology, 89, 181–186. Dulaney, C. L., Marks, W., & Link, K. E. (2004). Aging and directed forgetting: Pre-cue encoding and post-cue rehearsal effects. Experimental Aging Research, 30, 95–112.
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Earles, J. L., & Kersten, A. W. (2002). Directed forgetting of actions by younger and older adults. Psychonomic Bulletin & Review, 9, 383–388. Gardiner, J. M., Gawlik, B., & Richardson-Klavehn, A. (1994). Maintenance rehearsal affects knowing, not remembering: Elaborative rehearsal affects remembering, not knowing. Psychonomic Bulletin & Review, 1, 107–110. Geiselman, R. E., Rabow, V. E., Wachtel, S. L., & MacKinnon, D. P. (1985). Strategy control in intentional forgetting. Human Learning, 4, 169–178. Golding, J. M., & Gottlob, L. R. (2005). Recall order determines the magnitude of directed forgetting in the within-participants list method. Memory & Cognition, 33, 588–594. Horton, K. D., & Petruk, R. (1980). Set differentiation and depth of processing in the directed forgetting paradigm. Journal of Experimental Psychology: Human Learning & Memory, 6, 599–610. Hourihan, K. L., & MacLeod, C. M. (2008). Directed forgetting meets the production effect: Distinctive processing is resistant to intentional forgetting. Canadian Journal of Experimental Psychology, 62, 242–246. Lee, Y., Lee, H., & Fawcett, J. (in press). Intentional forgetting reduces color-naming interference: Evidence from item-method directed forgetting. Journal of Experimental Psychology: Learning, Memory, and Cognition. MacLeod, C. M. (1975). Long-term recognition and recall following directed forgetting. Journal of Experimental Psychology: Human Learning & Memory, 1, 271–279. MacLeod, C. M. (1989). Directed forgetting affects both direct and indirect tests of memory. Journal of Experimental Psychology: Learning, Memory, & Cognition, 15, 13–21. MacLeod, C. M. (1998). Directed forgetting. In J. M. Golding & C. M. MacLeod (Eds.). Intentional forgetting: Interdisciplinary approaches (pp. 1–57). Mahwah, NJ: Erlbaum. MacLeod, C. M. (1999). The item and list methods of directed forgetting: Test differences and the role of demand characteristics. Psychonomic Bulletin & Review, 6, 123–129. MacLeod, C. M., & Daniels, K. A. (2000). Direct vs. indirect tests of memory: Directed forgetting meets the generation effect. Psychonomic Bulletin & Review, 7, 354–359. Rundus, D. (1971). Analysis of rehearsal processes in free recall, Journal of Experimental Psychology, 89, 63–77. Tan, L., & Ward, G. (2000). A recency-based account of primacy effects in free recall. Journal of Experimental Psychology: Learning, Memory, & Cognition, 26, 1589–1625. Wetzel, C. D. (1975). Effect of orienting tasks and cue timing on the free recall of rememberand forget-cued words. Journal of Experimental Psychology, 1, 556–566. Wetzel, C. D., & Hunt, R. E. (1977). Cue delay and the role of rehearsal in directed forgetting. Journal of Experimental Psychology, 3, 233–245. Wilson, S. P., & Kipp, K. (1998). The development of efficient inhibition: Evidence from directed forgetting tasks. Developmental Review, 18, 86–123. Woodward, A. E., Bjork, R. A., & Jongeward, R. H. (1973). Recall and recognition as a function of primary rehearsal. Journal of Verbal Learning & Verbal Behavior, 12, 608–617.
Original manuscript received June 28, 2012 Final version accepted November 13, 2012
The Journal of General Psychology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vgen20
Costs and Benefits in ItemMethod Directed Forgetting: Differential Effects of Encoding and Retrieval Yuh-Shiow Lee
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National Chung-Cheng University Published online: 14 Jun 2013.
To cite this article: Yuh-Shiow Lee (2013) Costs and Benefits in Item-Method Directed Forgetting: Differential Effects of Encoding and Retrieval, The Journal of General Psychology, 140:3, 159-173, DOI: 10.1080/00221309.2012.750591 To link to this article: http://dx.doi.org/10.1080/00221309.2012.750591
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Costs and Benefits in Item-Method Directed Forgetting: Differential Effects of Encoding and Retrieval YUH-SHIOW LEE National Chung-Cheng University
ABSTRACT. This study examined how encoding and retrieval factors affected directed forgetting costs and benefits in an item-method procedure. Experiment 1 used a typical item-method procedure and revealed a levels-of-processing effect in overall recall. However, the deep encoding condition showed a smaller directed forgetting effect than the shallow encoding conditions. More importantly, “remember” (R) words were selectively rehearsed as indicated by greater recall from the primacy portion of the list and more apt to be recalled before “forget” (F) words. Experiment 2 showed that a deep encoding operation reduced directed forgetting costs and that directed forgetting benefits occurred only when R words were recalled before F words. These findings supported the hypotheses that encoding manipulation affected directed forgetting costs and that directed forgetting benefits were associated with output order bias. Results were discussed in terms of mechanisms that produce item-method directed forgetting. Keywords: levels-of-processing, output order, selective rehearsal, serial position curve
ONE OF THE METHODS USED TO EXAMINE INTENTIONAL forgetting is the directed forgetting paradigm. This paradigm includes two procedures to present instructional cues to participants regarding items they should forget or remember. In the item-method directed forgetting procedure, participants are given explicit cues for each to be forgotten (F) word, such as “forget,” and for each to be remembered (R) word, such as “remember.” The memory cue is typically presented after the relevant item to ensure that the participant has registered the study item and that each item receives the same amount of initial encoding. The The author would like to thank an anonymous reviewer for the suggestion and idea for conducting Experiment 2. This research was supported by Research Grant NSC-99-2410H-194-039-MY3 from the National Science Council of the Republic of China. Portions of this research were presented at the Association for Psychological Science 23rd Annual Convention, Washington, DC, USA. Address correspondence to Yuh-shiow Lee, Department of Psychology, National ChungCheng University, Chiayi 621, Taiwan, R. O. C.; [email protected] (e-mail). 159
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list method involves only one memory cue that is given in the middle of the list, usually an instruction to forget all of the preceding items. Studies using both procedures have demonstrated impaired memory for forget instructed relative to remember instructed items (see MacLeod, 1998, for a review). The difference in memory retention between F and R words is referred to as the directed forgetting effect. In the item-method procedure, both recognition and recall of F words are found to be impaired relative to R words (Basden & Basden, 1998; Basden, Basden, & Gargano, 1993; MacLeod, 1999; Wilson & Kipp, 1998). In recognition tests using the remember-know paradigm, participants made more “remember” responses for R words than for F words, but made a similar number of “know” responses regardless of the associated memory instruction (e.g., Gardiner, Gawlik & Richardson-Klavehn, 1994). Moreover, memory is impaired for F words on certain implicit memory tests, such as word-fragment and word-stem completion (MacLeod, 1989). The time and resources available for post-cue encoding had a larger effect on R than on F words (e.g., Davis & Okada, 1971; Macleod, 1989; Wetzel & Hunt, 1977). Based on these findings, several studies suggest that the item method, which differs from the list method, promotes selective rehearsal favoring the R words (Basden & Basden, 1998; Basden, Basden & Gargano, 1993; MacLeod 1999; Wilson & Kipp, 1998). This selective rehearsal account has been the major theory of item-method directed forgetting for decades (e.g., Bjork, 1972; MacLeod, 1975; Wetzel, 1975). Most studies on item-method directed forgetting compare F and R word retention within the same group of participants (the “remember-forget” group), who were asked to remember and forget certain words. In typical results of the item-method directed forgetting experiment, memory retention is better for R words than for F words because of worsened performance (costs) for F words and improved performance (benefits) for R words. Thus, the directed forgetting effect estimated from a single group of participants actually includes both directed forgetting costs and benefits. A directed forgetting cost is memory impairment for F words, whereas a directed forgetting benefit is memory gain for R words, as a result of the forget instruction. To separate directed forgetting costs and benefits, a control group (the “remember-all” group) receiving only “remember” cues is required. The control group provides a baseline for estimating memory improvement for R words and memory decline for F words in the “remember-forget group.” Directed forgetting costs can be estimated based on the difference in F word (the “remember-all” group actually has to remember these words) retention between the “remember-forget” and the “remember-all” groups. Directed forgetting benefits can be estimated from the difference in R word retention between these two groups. In item-method directed forgetting, all items receive maintenance rehearsal before the cue to remember or forget appears (Woodward, Bjork, & Jongeward, 1973). According to the selective rehearsal account, R word rehearsal continues and becomes elaborated, whereas F words do not receive such elaboration after
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cue presentation. As a result, R words retain a stronger, recollective memory trace relative to F words. The “remember-all” group, however, would try to rehearse all the study words. Thus, the directed forgetting costs presumably come from the difference in F word rehearsal during encoding between the “remember-forget” and the “remember-all” groups. The “remember-forget” group would stop to process F words (e.g., Lee, Lee, & Fawcett, in press) after the forget memory cue appears. If this is the case, then directed forgetting costs should also be affected by other types of levels-of-processing manipulations. During memory retrieval (e.g., a free recall test), the “remember-forget” group would be biased to recall R words prior to F words, because R words are better encoded and more accessible than F words, whereas the “remember-all” group would not show this kind of output order bias; all the study words would have the same chance to be retrieved. As a result, when retrieving R words, the “remember-all” group would experience greater output interference than the “remember-forget” group. In other words, the directed forgetting benefits for R words would come from the difference in output interference between the “remember-forget” and the “remember-all” groups. If this is the case, then an output order manipulation should affect directed forgetting benefits. Directed forgetting benefits should occur only when R words are recalled before F words. The two experiments reported in this study were designed to test the above hypotheses regarding the origins of directed forgetting costs and benefits in itemmethod directed forgetting. In this paradigm, previous studies suggest that R words are better remembered than F words because R words have benefited from more rehearsal following initial encoding. This differential rehearsal would have less or no effects on study words that have been processed deeply. For a deeply encoded F word, an instruction to forget should have a limited effect on retention, as compared with a shallowly encoded F word (see MacLeod & Daniels, 2000; Houriham & MacLeod, 2008). This limitation would reduce the directed forgetting costs because it decreases encoding differences of F words between the “rememberforget” and the “remember-all” groups. Furthermore, if the directed forgetting benefits for R words, as mentioned above, come from reduced output interference for the “remember-forget” group, then it should appear only when R words are recalled before F words and should be reduced or diminished when F words are recalled before R words. Several previous studies examined the levels-of-processing effect on itemmethod directed forgetting. However, the results were mixed. They suggest either no difference in the directed forgetting effect between the shallow and deep processing conditions (Dulaney, Marks, & Link, 2004; although in Experiment 1, the directed forgetting effect from the recognition test was reduced in the deep encoding condition) or that the deep processing condition had a smaller directed forgetting effect than the shallow processing condition (Wetzel, 1975; Geiselman, Rabow, Wachtel, & MacKinnon, 1985). One study found a larger directed forgetting effect in the deep processing condition (Horton & Petruk, 1980). The results
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of Horton and Petruk (1980) may have been due to their unusual manipulations of list categorical structures and timing of the levels-of-processing tasks. The purpose of Experiment 1 was to use a typical item-method procedure and a standard levels-of-processing manipulation to examine this possibility. More importantly, before directly testing the above hypotheses regarding directed forgetting benefits and costs, it is important to provide more direct evidence for the notion that in a typical item-method procedure participants selectively rehearse R words, but not F words and tend to recall R words before F words in a free recall test. The selective rehearsal account is often inferred from the result that R words were recalled and recognized better than F words. To provide direct evidence for the selective rehearsal of R words, Experiment 1 compared R word and F word recall under serial position analyses focusing on the primacy region and recency region of the serial position curve. Previous studies have suggested that the primacy effect is due to the tendency to rehearse the first few study words (Rundus, 1971; Tan & Ward, 2000). The selective rehearsal account predicts that the recall difference between R words and F words should mainly come from the primacy region of the cure. Experiment 2 directly tested the proposed hypotheses by manipulating both the encoding operation and recall order to examine their effects on directed forgetting costs and benefits. Experiment 1 Experiment 1 had two purposes. First, this experiment examined the levels-ofprocessing manipulation on item-method directed forgetting. Second, this experiment tried to provide more direct evidence that, in a typical item-method directed forgetting involving free recall, participants would rehearse R words but not F words, and would tend to recall R words before F words. Method Participants and Design All the participants in this study were native Chinese speakers. To partially fulfill course requirements, 28 university students taking introductory psychology courses participated voluntarily. This experiment was a 2 by 2 within-subjects design. The two independent variables were the encoding operation (shallow vs. deep processing) and memory cue (remember vs. forget) following each study word. Materials Forty two-character Chinese words from different categories were selected. All the words were high frequency concrete nouns. They were divided into two
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sets of twenty words and assigned “forget” and “remember” cue conditions. Furthermore, one-half of the words in each set were paired with the processing cue word “” (stroke) and the other half were given the processing cue word “ ” (good-bad). The assignment of each set was counterbalanced, so that each word had an equal chance to receive “forget” and “remember” cues and to be paired with “stroke” or “good-bad” processing cues. The experiment was run on a personal computer. The viewing distance was 50 cm and the character size was 3 cm × 3.5 cm. Procedure Participants were tested individually. Each experimental session consisted of a study phase and a testing phase. During the study phase, participants studied the forty words one by one. A processing cue word, “” (stroke) or “” (goodbad), appeared below each study word. For each study word, participants had to judge which of the two characters of the study word had more strokes when the processing cue word “stroke” appeared. They also had to judge whether the study word had a good or bad connotation when the cue word “good-bad” appeared. Participants responded orally by saying “left (or right)” or “good (or bad)”. After studying each word for five seconds, participants were given a cue to remember or forget the study word. The cue remained on the screen for 2.5 seconds. The next study word and processing cue appeared after a 0.5-second blank screen. The presentation order of the study words and cue words was randomly determined. However, the same type of cue word, either a processing cue or memory cue word, would not appear for more than three consecutive trials. Participants performed a free recall test after studying all the words. They were instructed to recall in any order as many of the study words as possible, regardless of whether they were “forget” words or “remember” words and write down their answers on a piece of paper. After the experiment was over, participants were instructed not to discuss the experiment with other potential participants. Results The following analyses are based on the correct recall rate focusing separately on the serial position curve and the recall order. Serial Position Analyses For each position n, the serial position curve was smoothed by averaging original data, with the exception of the first and the last positions of the curve, from three adjacent points, Xs (n) = [X(n – 1) + X(n) + X(n − 1)]/3. The first and the last positions were averaged based on two adjacent points, Xs(1) = [X(1) + X(2)]/2 and Xs(last) = [X(last − 1) + X(last)]/2. Figure 1 shows the results. To
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FIGURE 1. Serial position curve for remember and forget word recall as a function of encoding operation and position.
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TABLE 1. Mean Rates of Correct Free Recall as a Function of Encoding Operation and Memory Cue (Standard Errors in Parentheses) in Experiment 1
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examine the serial position effect, the analyses first combined positions 1 to 3 (primacy), positions 4 to 7 (middle) and position 8 to 10 (recency). A 2 (encoding operation: deep vs. shallow) by 2 (memory cue: forget vs. remember cue) by 3 (position: primacy vs. middle vs. recency) ANOVA was then performed. The analyses showed significant main effects of encoding operation, memory cue, and serial position [F(1, 27) = 14.68, MSe = .08, p < .001, η2p = .35; F(1, 27) = 112.94, MSe = .09, p < .001, η2p = .81; and F(2, 54) = 4.19, MSe = .04, p < .05, η2p = .13, respectively]. More importantly, the interaction effect between memory cue and position was also significant [F (2, 54) = 14.07, MSe = .04, p < .001, η2p = .33]. The interaction effect between encoding operation and memory cue was marginally significant [F (1, 27) = 3.80, MSe = .07, p < .062, η2p = .12]. No other reliable interaction effects were found (all F’s < 1). Post-hoc tests showed that R words in the primacy region were recalled better than both the middle and recency regions (M = .69 vs. M = .59 and M = .60; both p’s < .05). F words in the recency region were recalled better than both the primacy and middle regions (M = .40 vs. M = .20 and M = .25; both p’s < .001). These results indicated that R words showed a primacy effect, whereas F words only revealed a recency effect. As for the interaction between encoding operation and memory cue (see Table 1), post-hoc tests revealed that both the shallow processing and deep processing conditions showed significant directed forgetting effects (Mdf = .39 and Mdf = .28; both p’s < .001). The F words showed a significant levels-of-processing effect (Mlop = .16; p < .01), whereas R words did not (Mlop = .06; p = .48). Analyses of Recall Order Correlations were calculated on the serial position of each word on the recall list and the type of words to examine whether participants were more apt to recall R words before F words and deeply processed words before shallowly processed words. Dummy codes were used to index that R words and deeply processed words (e.g., coded as “1”) were recalled before F words and shallowly
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processed words (e.g., coded as “2”). Thus, a positive correlation indicated that R words were recalled on the average earlier in output than F words and deeply processed words were recalled earlier than shallowly processed words. Across all the participants the correlation between serial position and whether a word was followed by an F or R memory cue was significant [r = .29, t(476) = 6.52, p < .001], whereas the correlation between serial position and whether a word was deeply or shallowly processed was not significant [r = −.08, t(476) = − 1.66, p = .11]. Furthermore, 23 out of 28 (82%) participants began their recall with an R word, 21 out of 28 (75%) participants started their recall with two R words, and 17 out of 28 (61%) participants started their recall with three R words. These results suggest that participants tended to recall R words before F words in the free recall test. Discussion This experiment found a typical levels-of-processing effect for the F words and not the R words. Furthermore, the shallowly processed words revealed a larger directed forgetting effect than the deeply processed words. Consistent with the proposed hypothesis, for the deeply processed words, because initial encoding has optimized memory performance, the normal effect of the “forget” instruction was reduced. Experiment 1 also demonstrated that, in a typical item-method directed forgetting paradigm involving free recall, R words were recalled before F words during retrieval. The directed forgetting effect in this experiment, estimated by comparing R word and F word recall within a group, presumably came from two different sources. First, according to the serial position analyses, R words, but not F words, showed a primacy effect suggesting that participants selectively rehearsed R words. As indicated by the recency effect, the rate of F word recall was mainly determined by the decay of memory strength over time; later presented items were remembered better than those presented earlier. There was little evidence to suggest that participants rehearsed F words, either intentionally or accidentally. Second, recall order analyses indicated that in the free recall test, participants tended to recall R words before F words, regardless of types of encoding operation. The bias in recall order should have also contributed to the directed forgetting effect. Experiment 2, including a “remember-all” control group, was designed to test directly the hypothesis that selective rehearsal and output bias are associated with different sources of the directed forgetting effect. Experiment 2 Experiment 2 aims to test the hypothesis that directed forgetting costs and benefits in the item-method are associated with different mnemonic factors involving either encoding or retrieval processes. This experiment manipulated both
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the encoding operation and recall order. The encoding manipulation was the same as that of Experiment 1. However, participants in Experiment 2 had to perform a cued recall, instead of a free recall test. During testing, a categorical cue was given to the participants to control recall order. A control group who only received the “remember” cue was included to estimate directed forgetting costs and benefits. Method Participants and Design Sixty-four university students taking introductory psychology courses voluntarily participated to fulfill course requirements. This experiment was a 2 by 2 by 2 by 2 mixed design. Encoding operation (shallow vs. deep processing) and memory cue (remember vs. forget) following each study item were the withinsubjects factors. The between-subjects factors were recall order (R word first vs. F word first) and memory group (remember-forgetting vs. remember-all group). There were 16 participants in each of the 4 between-subjects combinations of conditions. Materials The study materials were the same forty two-character Chinese words used in Experiment 1. They belonged to different taxonomic categories and forty categorical names were used as retrieval cues during the final memory test. Procedure The procedures were the same as those of Experiment 1, with two exceptions. First, during the final recall test, participants had to perform a cue recall, instead of a free recall test. Participants were asked to recall the study words when a categorical name appeared in the center of a computer screen. The recall order, determined by the retrieval cue, was manipulated between participants. Half of the participants recalled “remember” words before “forget” words. The other group of participants recalled “forget” words before “remember” words. The categorical names were presented randomly within each type of memory cue. The random sequence was different for each participant. Second, a control (“remember-all”) group was included. The remember-all and experimental (“remember-forget”) groups were yoked; each participant in the remember-all group was assigned for each participant in the remember-forget group. The remember-all group of participants followed an identical procedure and design as the remember-forget group, except that during the study phase all the “forget” cues were replaced by the
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“remember” cues. Thus, the remember-all group only received the “remember” cues. Participants were told that the “remember” cue was used to remind them to remember each study words. Participants were instructed not to discuss the experiment with other potential participants after the experiment was over.
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Results Table 2 presents the mean rates of correct recall. The only difference between the “remember-all” and “remember-forget” groups was that, for the “rememberall” group, the “remember” cue replaced the “forget” cue. The recall rate of the remember-all group was analyzed in the same manner as the remember-forget group. F words for the remember-all group were actually the study words that they were asked to remember. A 2 (encoding operation: deep vs. shallow) by 2 (memory cue: forget vs. remember cue) by 2 (memory group: remember-forgetting vs. remember-all group) by 2 (recall order: R word first vs. F word first) ANOVA was performed. Both main effects of encoding operation and memory cue were significant [F (1, 60) = 60.25, MSe = .02, p < .001, η2p = .50; and F (1, 60) = 26.63, MSe = .03, p < .001, η2p = .31, respectively.] The interactions between memory cue and memory group and between encoding operation and memory cue were also significant [F (1, 60) = 17.48, MSe = .03, p < .001, η2p = .23; and F (1, 60) = 4.18, MSe = .02, p < .05, η2p = .07, respectively.] The three-way interaction between encoding operation, memory cue, and memory group was significant [F (1, 60) = 8.25, MSe = .02, p < .01, η2p = .12.] All other effects were not reliable (all p > .12). The inclusion of the remember-all group enabled the present study to estimate
TABLE 2. Mean Rates of Correct Cued Recall as a Function of Group, Memory Cue, Encoding Operation, and Recall Order (Standard Errors in Parentheses) in Experiment 2 Remember-forget group F word Recall order R – F order F – R order
.65 (.04) .72 (.05)
R – F order F – R order
.44 (.04) .45 (.05)
R word
Remember-all group F(R) word
Deep processing .84 (.02) .67 (.05) .77 (.03) .73 (.04) Shallow processing .77 (.02) .56 (.05) .71 (.05) .66 (.05)
R word .72 (.04) .75 (.04) .55 (.07) .68 (.04)
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separately the directed forgetting benefits and costs. In the following these two effects were analyzed separately.
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Directed Forgetting Benefits For R Words As mentioned above, the directed forgetting benefit refers to the differences in the recall of R words between the “remember-all” and “remember-forget” groups. A 2 (encoding operation: deep vs. shallow processing) by 2 (group: “rememberall” vs. “remember-forget” group) by 2 (recall order: R word first vs. F word first) ANOVA was performed on the recall of R words. The main effects of both encoding operation and group were significant [F(1, 60) = 22.77, MSe = .01, p < .001, η2p = .28 and F(1, 60) = 6.96, MSe = .04, p < .05, η2p = .10, respectively.] R words in the deep processing condition were recalled more than those in the shallow processing condition were (M = .68 vs. M = .53). The interaction between group and recall order was also significant [F(1, 60) = 3.96, MSe = .04, p < .052, η2p = .06.] Post hoc tests showed that when R words were recalled before F words, the “remember-forget” group recalled more R words than the “rememberall” group (M = .80 vs. M = .64; p < .01). There was no difference between “remember-forget” and “remember-all” groups (M = .74 vs. M = .72) when F words were recalled before R words (the F-R order). These results indicate that directed forgetting benefits occurred only when participants recalled in the R-F order. Directed Forgetting Costs For F Words The directed forgetting cost refers to the differences in the recall of F words between the “remember-all” and “remember-forget” groups. To analyze directed forgetting costs, a 2 (encoding operation: deep vs. shallow processing) by 2 (group: remember-all vs. remember-forget group) by 2 (recall order: R word first vs. F word first) ANOVA was performed on F word recall. The main effects of encoding operation and group were significant [F(1, 60) = 37.36, MSe = .02, p < .001, η2p = .38 and F(1, 60) = 5.97, MSe = .04, p < .05, η2p = .09, respectively.] More importantly, there was a significant interaction between group and encoding operation [F(1, 60) = 7.12, MSe = .02, p < .01, η2p = .11.] Post hoc tests showed that the difference in recall of F words between “remember-forget” and “remember-all” groups was found in the shallow processing condition (M = .44 vs. M = .61; p < .01), and not in the deep processing condition (M = .68 vs. M = .70). Apparently, only the shallow processing condition produced directed forgetting costs. Discussion In this experiment, the output order was controlled and directed forgetting costs for F words and benefits for R words were estimated separately by including
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a control (remember-all) group that was required to remember all the study words. The results provided clear evidence that directed forgetting benefits for R words occurred only when participants recalled R words before F words. In addition, only the shallow processing condition produced directed forgetting costs for F words. These results are consistent with the current hypotheses. First, encoding operation is associated with directed forgetting costs for F words because as compared with the shallowly processed F words, the deeply processed F words were better (deeply) encoded and thus less sensitive to the forgetting cue. In addition, directed forgetting benefits for R words come from a difference in the recall order between R words and F words because, as compared with the R-F recall order, the F-R recall order reduced the benefits of R word recall in the remember-forget group. General Discussion The inclusion of a control group that was asked to remember all the study words allowed the current study to separately estimate directed forgetting costs for F words and benefits for R words. The results revealed that directed forgetting costs were related to the encoding operation. The deeply processed F words were less sensitive to the forgetting cue. As a result, directed forgetting costs in the deep processing condition were reduced as indicated by the comparison of F word retention between the “remember-forget” and control (“remember-all”) groups. Furthermore, directed forgetting benefits for R words were sensitive to recall order. When output order was directly manipulated, directed forgetting benefits were found only when R words were recalled before F words. These findings are consistent with the proposed hypotheses that directed forgetting costs for F words come from encoding and directed forgetting benefits for R words are related to retrieval factors. Several previous studies examined the effect of levels-of-processing manipulations on item-method directed forgetting (Dulaney, Marks, & Link, 2004; Geiselman et al., 1985; Horton & Petruk, 1980; Wetzel, 1975). However, they showed inconsistent results. Other studies examined effects similar to that from the levelsof-processing manipulation. MacLeod and Daniels (2000) report that the cue to forget affected “read” words but not “generated” words in free recall. In addition, participants were more apt to intentionally forget verbally encoded items than the self-perform action (Earles & Kersten, 2002). Similarly, an encoding operation that creates the production effect was not susceptible to the instruction to forget (Houriham & MacLeod, 2008). These findings suggest that strong item-specific and distinctive processing from encoding operation such as production or generation overrode the effect of forget memory instruction. In other words, a directed forgetting instruction cannot influence words that have been encoded distinctively. None of the above studies separated costs and benefits of directed forgetting or controlled order of recall. An analysis that includes only the “remember-forget” group and combines the two recall orders was carried out to directly compare
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the current result of Experiment 2 with those from previous studies. The results showed significant main effects of both encoding operation and memory cue, F(1, 31) = 46.42, MSe = .02, p < .001, η2p = .58; and F(1, 31) = 51.04, MSe = .03, p < .001, η2p = .62, respectively. The interaction effect was also reliable, F(1, 31) = 16.52, MSe = .01, p < .001, η2p = .35. The directed forgetting effect, the difference between R and F word recall within the same group of participants, was found for both the shallow (M = .74 vs. M = .44) and deep conditions (M = .81 vs. M = .68). The deep condition nonetheless revealed a smaller directed forgetting effect than the shallow condition. This result was similar to that of Experiment 1 in which directed forgetting benefits and costs were not separated. The directed forgetting effect found in both Experiments 1 and 2 was reduced, but not eliminated as that found in previous studies (Earles & Kersten, 2002; Houriham & MacLeod, 2008; MacLeod & Daniels, 2000). Participants in the present study were asked to make a semantic judgment in the deep encoding condition. This type of semantic encoding seems not as distinctive as that from production and generation which involve strong item-specific processing. Thus, the forget memory instruction still had some effects on memory performance. However, the directed forgetting cost was eliminated for the deeply processed words in Experiment 2 when the directed forgetting costs and benefits were separated. Since the directed forgetting cost was eliminated, the small directed forgetting effect for the deeply processed words found in both Experiments 1 and 2 should mainly come from the R-F recall order (the directed forgetting benefits). When F words were very well-remembered as a result of distinctive processing (e.g., Earles & Kersten, 2002; Houriham & MacLeod, 2008; MacLeod & Daniels, 2000), it was very likely that even the R-F recall order would not produce a directed forgetting (benefit) effect. In Experiment 1, the directed forgetting effect was large (.39) for the shallowly processed words for which participants had to judge which of the two characters of the study word had more strokes. This was essentially a structural complexity judgment. The study words in this condition were very shallowly processed, as indicated by the low recall rate (less than .20) for the first half of F words in the serial position (see Figure 1). Most of the recalled F words came from the last four words in the study list which was presumably still held in short-term memory at the time of the memory test. The shallowly processed R words had the benefit of rehearsal, whereas the shallowly processed F words suffered from lack of rehearsal, shallow encoding and output later than R words. Thus, the present study observed a large directed forgetting effect for the shallow processing condition in a free recall test. The cue recall test, used in Experiment 2 to control the recall order, is different from the free recall test used in most of the directed forgetting experiments. It is useful to compare results from these two procedures. The deeply processed F words benefitted more from cued recall (from .36 in free recall to .69 in cued recall) than the shallowly processed F words did (from .19 to .45). In other words,
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the improvement from free recall to cued recall was more obvious for the deeply processed F words. Thus, given that in both free recall and cued recall R words showed a small levels-of-processing effect, the magnitude of directed forgetting effect in Experiment 2 was significantly reduced (from .28 in Experiment 1 to .12 in Experiment 2) for the deep processing condition, relative to the shallow processing condition (from .38 in Experiment 1 to .30 in Experiment 2). This finding that a retrieval cue facilitated retrieval of the deeply processed F words more than the shallowly processed F words further confirms the effective levels-of-processing manipulation during encoding in the present study. To my knowledge, the present study is the first to demonstrate a dissociation between the effects of directed forgetting costs and benefits in an item-method directed forgetting paradigm and their differential associations with encoding and retrieval factors. Most of the studies attribute the item-method directed forgetting effect to encoding difference between R and F words; however, the magnitude of this effect is inflated by the R-F recall order. A similar result that directed forgetting occurred only when R words were recalled before F words has also been found using the list-method procedure (Golding & Gottlob, 2005). Therefore, controlling recall order should be an important methodological consideration for studies using the item-method procedure. Moreover, the analyses of directed forgetting costs and benefits in the item-method, just as in the list-method -method can provide useful information in understanding specific mechanisms that create this type of intentional forgetting. AUTHOR NOTE Yuh-shiow Lee is a Professor at National Chung-Cheng University, Taiwan, R.O.C. She earned her doctorate at Stony Brook University. Her research is focused on human learning and memory.
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Original manuscript received June 28, 2012 Final version accepted November 13, 2012
