Learning and forgetting in schizophrenia

Recent studies of patients with schizophrenia have consistently demonstrated marked deficits on measures of initial learning. However, contradictory results have been reported concerning retention and forgetting. The present study examined the level of initial and delayed recall of stories and visual figures in a group of 76 patients with schizophrenia and 51 normal controls. Schizophrenia patients demonstrated marked impairments in initial and delayed recall as well as significantly worse percentage retention scores. However, schizophrenia patients and healthy controls individually matched on level of initial recall had nearly identical delayed recall performance. The results suggest a primary deficit in the initial acquisition of information rather than an accelerated rate of forgetting in schizophrenia.     

Decomposing serial learning: What is missing from the learning curve?

Our current understanding of serial learning relies on the form of the learning curve and on changes in the serial position curve over repeated study-test trials (Ward, 1937). The averaging of data that produces these functions obscures the detailed history of memory for individual items over the course of study-test trials. Extending Tulving’s (1964) analysis of free recall learning, we present a new analysis of serial learning that tracks the acquisition and forgetting of item and order information at the level of individual items. Applying this analysis to two large data sets on serial list learning allows us to discern among hypotheses that are indistinguishable solely on the basis of the learning curve.     

The role of outcome inhibition in interference between outcomes: A contingency‐learning analogue of retrieval‐induced forgetting

Current associative theories of contingency learning assume that inhibitory learning plays a part in the interference between outcomes. However, it is unclear whether this inhibitory learning results in the inhibition of the outcome representation or whether it simply counteracts previous excitatory learning so that the outcome representation is neither activated nor inhibited. Additionally, these models tend to conceptualize inhibition as a relatively transient and cue‐dependent state. However, research on retrieval‐induced forgetting suggests that the inhibition of representations is a real process that can be relatively independent of the retrieval cue used to access the inhibited information. Consistent with this alternative view, we found that interference between outcomes reduces the retrievability of the target outcome even when the outcome is associated with a novel (non‐inhibitory) cue. This result has important theoretical implications for associative models of interference and shows that the empirical facts and theories developed in studies of retrieval‐induced forgetting might be relevant in contingency learning and vice versa.     

Divided attention facilitates intentional forgetting: evidence from item-method directed forgetting

This study examined the effects of post-cue interval and cognitive load on item-method directed forgetting. The results of Experiment 1 (free recall test) and Experiment 2 (cued recall test) showed that forget item retention increased as the post-cue interval increased. Moreover, increasing the cognitive load of participants by asking them to perform a secondary counting task did not impair, but rather facilitated, the intentional forgetting of the studied item under long post-cue interval conditions. These results and analyses of recall gains from the additional use of the independent cue suggest that the improved recall of forget items caused by an increase in the post-cue interval came from an automatic process, and that after receiving the forget cue, participants did not engage a suppression operation that was resource-demanded. The current findings suggest that forgetting is more effective when participants perform a secondary task after receiving the forget cue.     

Brief wakeful resting can eliminate directed forgetting

When cued to intentionally forget previously encoded memories, participants typically show reduced recall of the memories on a later recall test. We examined how such directed forgetting is affected by a brief period of wakeful resting between encoding and test. Encoding was followed by a “passive” wakeful resting period in which subjects heard emotionally neutral music or perceived neutral pictures, or it was followed by an “active” distraction period in which subjects were engaged in counting or calculation tasks. Whereas typical directed forgetting was present after active distraction, the forgetting was absent after wakeful resting. The findings indicate that the degree to which people can intentionally forget memories is influenced by the cognitive activity that people engage in shortly after learning takes place. The results provide first evidence on the interplay between wakeful resting and intentional forgetting.     

Direct remembering,mediated remembering,and atypical forgetting functions

Atypical forgetting functions have been demonstrated in several recent studies of delayed matching to sample, in which experimental conditions are altered partway through the retention interval. The forgetting functions are atypical in that accuracy or discriminability is not always a negatively accelerated monotonic function of increasing retention interval duration, but may increase at later times in the retention interval. Atypical forgetting functions reflect changes in levels of discrimination. A switch from a lower level to a higher level of discrimination, or vice versa, can occur at any time in the retention interval. The behavioral theories of remembering proposed by Nevin, Davison, Odum, and Shahan (2007), and White and Brown (2014), offer quantitative predictions of forgetting functions that differ in intercept or slope. Both theories are able to account for atypical forgetting functions, by assuming time‐independent changes in the mediating effect of attending to sample and comparison stimuli (in Nevin et al.'s model) or in the direct effect of the context of reinforcement of the conditional discrimination (in White & Brown's model). Despite differences in their main assumptions, the theories have an edge over any theory that assumes that forgetting is time‐dependent.     

The role of intentional forgetting in reducing children's retroactive interference.

Preschool and kindergarten children's retention of stories was examined in the presence of interfering information and instructions to forget. Children learned 2 stories and, 24 hr later, were asked to recall the 1st or 2nd story learned. Some of the children were instructed, either following acquisition or just prior to the retention test, to forget the 2nd, or interfering, story. A model was used to isolate storage and retrieval effects, and the results showed that (a) retroactive interference affected both storage- and retrieval-based forgetting rates for the younger children but only storage-based forgetting rates for the older children, (b) intentional forgetting reduced retroactive interference primarily by attenuating storage-based forgetting regardless of age, (c) intentional forgetting instructions were effective only at acquisition for preschoolers but at both acquisition and retention for kindergarteners, and (d) all children recalled the to-be-forgotten story as well as they recalled the to-be-remembered story. These results are interpreted in terms of reorganization and distinctiveness effects in storage.     

Predicting one's own forgetting: the role of experience-based and theory-based processes

The authors examined the hypothesis that judgments of learning (JOL), if governed by processing fluency during encoding, should be insensitive to the anticipated retention interval. Indeed, neither item-by-item nor aggregate JOLs exhibited "forgetting" unless participants were asked to estimate recall rates for several different retention intervals, in which case their estimates mimicked closely actual recall rates. These results and others reported suggest that participants can access their knowledge about forgetting but only when theory-based predictions are made, and then only when the notion of forgetting is accentuated either by manipulating retention interval within individuals or by framing recall predictions in terms of forgetting rather than remembering. The authors interpret their findings in terms of the distinction between experience-based and theory-based JOLs.     

Can intentional forgetting reduce false memory? Effects of list-level and item-level forgetting

This study examined whether false memory produced by the learning of lists of categorized and associative materials could be reduced by directed forgetting. The number of items within a list that participants were asked to remember or forget was manipulated, while the length of the list remained constant. Experiment 1a used categorized lists and Experiment 1b used associative lists; the participants performed immediate free recall and cued recall tests. For both the categorized and associative lists, the rate of false recall increased upon increasing the proportion of "forget" (F) words. After removing the immediate recall test, Experiment 2 found that intentionally forgetting part of the studied list reduced false memory, whereas forgetting the whole studied list did not. The results are discussed in terms of the list-level-vs.-item-level inhibition in semantic activation and the role of monitoring in reducing false memory.     

Effects of testing on subsequent re‐encoding and long‐term forgetting of action‐relevant materials: On the influence of recall type

Testing one's memory of previously studied information reduces the rate of forgetting, compared to restudy. However, little is known about how this direct testing effect applies to action phrases (e.g., “wash the car”) – a learning material relevant to everyday memory. As action phrases consist of two different components, a verb (e.g., “wash”) and a noun (e.g., “car”), testing can either be implemented as noun‐cued recall of verbs or verb‐cued recall of nouns, which may differently affect later memory performance. In the present study, we investigated the effect of testing for these two recall types, using verbally encoded action phrases as learning materials. Results showed that repeated study–test practice, compared to repeated study–restudy practice, decreased the forgetting rate across 1 week to a similar degree for both noun‐cued and verb‐cued recall types. However, noun‐cued recall of verbs initiated more new subsequent learning during the first restudy, compared to verb‐cued recall of nouns. The study provides evidence that testing has benefits on both subsequent restudy and long‐term retention of action‐relevant materials, but that these benefits are differently expressed with testing via noun‐cued versus verb‐cued recall.     

Directed forgetting in incidental learning and recognition testing: support for a two-factor account

Instructing people to forget a list of items often leads to better recall of subsequently studied lists (known as the benefits of directed forgetting). The authors have proposed that changes in study strategy are a central cause of the benefits (L. Sahakyan & P. F. Delaney, 2003). The authors address 2 results from the literature that are inconsistent with their strategy-based explanation: (a) the presence of benefits under incidental learning conditions and (b) the absence of benefits in recognition testing. Experiment 1 showed that incidental learning attenuated the benefits compared with intentional learning, as expected if a change of study strategy causes the benefits. Experiment 2 demonstrated benefits using recognition testing, albeit only when longer lists were used. Memory for source in directed forgetting was also explored using multinomial modeling. Results are discussed in terms of a 2-factor account of directed forgetting.     

Different rates of forgetting following study versus test trials

Two experiments investigated recall following two study conditions, (1) repeated test: a study trial followed by multiple recall trials, and (2) repeated study: multiple study trials with no tests. At a retention interval of 5 minutes, repeated study produced a higher level of recall than repeated test. When the retention interval was extended, forgetting was much more rapid in the study condition, with the repeated test manipulation leading to higher recall at an interval of 7 days. We conclude that study and test trials have different effects upon memory, with study trials promoting memory acquisition, and test trials enhancing the retrieval process itself, which protects against subsequent forgetting.     

Different rates of forgetting following study versus test trials

Two experiments investigated recall following two study conditions, (1) repeated test: a study trial followed by multiple recall trials, and (2) repeated study: multiple study trials with no tests. At a retention interval of 5 minutes, repeated study produced a higher level of recall than repeated test. When the retention interval was extended, forgetting was much more rapid in the study condition, with the repeated test manipulation leading to higher recall at an interval of 7 days. We conclude that study and test trials have different effects upon memory, with study trials promoting memory acquisition, and test trials enhancing the retrieval process itself, which protects against subsequent forgetting.     

Costs and Benefits in Item-Method Directed Forgetting: Differential Effects of Encoding and Retrieval

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.     

Where is the forgetting with list-method directed forgetting in recognition?

Despite the fact that list-method directed forgetting instruction leads to decreases in memory performance on tests of free recall, there are to date no published reports of comparable effects in recognition testing. In the present article, we evaluated whether conditions that promote the importance of context in recognition, either via stimulus selection (Experiments 1 and 2) or by test choice (Experiment 3), elicit directed forgetting impairment. In all three experiments, we obtained reliable recognition deficits, suggesting that the typical conditions of recognition, rather than recognition itself, underlie the discrepancy between the tests of recognition and free recall in list-method directed forgetting.     

Forgetting curves: implications for connectionist models

Forgetting in long-term memory, as measured in a recall or a recognition test, is faster for items encoded more recently than for items encoded earlier. Data on forgetting curves fit a power function well. In contrast, many connectionist models predict either exponential decay or completely flat forgetting curves. This paper suggests a connectionist model to account for power-function forgetting curves by using bounded weights and by generating the learning rates from a monotonically decreasing function. The bounded weights introduce exponential forgetting in each weight and a power-function forgetting results when weights with different learning rates are averaged. It is argued that these assumptions are biologically reasonable. Therefore power-function forgetting curves are a property that may be expected from biological networks. The model has an analytic solution, which is a good approximation of a power function displaced one lag in time. This function fits better than any of the 105 suggested two-parameter forgetting-curve functions when tested on the most precise recognition memory data set collected by. Unlike the power-function normally used, the suggested function is defined at lag zero. Several functions for generating learning rates with a finite integral yield power-function forgetting curves; however, the type of function influences the rate of forgetting. It is shown that power-function forgetting curves cannot be accounted for by variability in performance between subjects because it requires a distribution of performance that is not found in empirical data. An extension of the model accounts for intersecting forgetting curves found in massed and spaced repetitions. The model can also be extended to account for a faster forgetting rate in item recognition (IR) compared to associative recognition in short but not long retention intervals.     

延时间隔和线索类型对遗忘学习判断的影响*

主要探讨不同延时间隔和线索类型对遗忘元认知判断的影响。采用传统的学习判断任务,让被试学习40对无意义配对词,并告知随后进行测试,当呈现第一个词时,被试能够回忆与之配对的后一个词。让被试预测当延迟不同时间（5分钟、1天和1周）进行测试时,他们能够记住（学习判断）或者遗忘（遗忘判断）后一词的可能性。最后,要求被试回忆所有词对。结果发现延时间隔对学习判断和遗忘判断有相似的影响;学习判断的等级和相对准确性均高于遗忘判断,说明人们对记住和遗忘的线索很敏感;相比于学习判断,人们监测自己遗忘能力的信心不足。研究结果表明人们能够利用延时间隔和线索类型来预测未来的测验成绩,对遗忘的监测能力低于对记住的监测。     

The effects of dopamine D(1) receptor blockade in the prelimbic-infralimbic areas on behavioral flexibility

This study examined the effects of a dopamine D₁ antagonist, SCH23390, infused into the prelimbic–infralimbic areas on the acquisition of a response and visual-cue discrimination task, as well as a shift from a response to a visual-cue discrimination and vice versa. Each test was carried out in a cross-maze. The response discrimination required learning to always turn in the same direction (right or left) for a cereal reinforcement. The visual-cue discrimination required learning to always enter the arm with the visual cue. In experiment 1, rats were tested on the response discrimination task, followed by the visual-cue discrimination task. In experiment 2, the testing order was reversed. Bilateral infusions of SCH23390 (0.1 or 1 μg/0.5 μL) into the prelimbic–infralimbic areas did not impair acquisition of the response or visual-cue discrimination tasks. SCH23390 injections at 1 μg, but not 0.1 μg impaired performance when shifting from a response to a visual-cue discrimination, and vice versa. Analysis of the errors revealed that the deficit was due to perseveration of the previously learned strategy. These results suggest that activation of dopamine D₁ receptors in the prelimbic–infralimbic areas may be critical for the suppression of a previously relevant strategy and/or generating new strategies.     

BRIEF REPORT Forgetting “murder” is not harder than forgetting “circle”: Listwise-directed forgetting of emotional words

The list-method directed forgetting (DF) paradigm has attracted the attention of clinical psychologists because it is widely believed that a retrieval inhibition mechanism underlies its effects. Thus, the idea is that people are capable of intentionally forgetting negative emotional material. On the other hand, there are reasons to believe that negative stimuli are relatively resistant to forgetting. The present experiment compared listwise DF of emotional and neutral words in healthy college students. A modified procedure (i.e., a simulated computer crash) showed a reliable DF-effect in that list 1 recall was larger under remember than forget instructions whereas the reverse was true for list 2 recall. Emotionality did not modulate the magnitude of this effect. Thus, negative emotional material is not resistant to forgetting. Although overall, the present findings are in line with a retrieval inhibition interpretation (i.e., decreased access to list 1 material), attentional focusing during list 2 learning may provide a sufficient explanation.     

Providing corrective feedback during retrieval practice does not increase retrieval-induced forgetting

Recalling a subset of studied materials can impair subsequent retrieval of related, nontested materials. In two experiments, we examined the influence of providing corrective feedback (no feedback, immediate feedback, delayed feedback) during retrieval practice on this retrieval-induced forgetting effect. Performance was assessed with category cued recall (e.g., recall all exemplars studied under Weather), category-and-stem cued recall (e.g., Weather–B___), and recognition. We report a dissociation between the effects of feedback on memory of the tested materials and the nontested materials. Whereas providing immediate or delayed feedback (compared to no feedback) improved recall and recognition of the tested items, it had no influence on retrieval-induced forgetting. These results are consistent with the inhibition account of retrieval-induced forgetting. From an applied perspective, this finding is encouraging for students and educators who use testing to foster learning.