Context learning and the effect of context on memory retrieval in Lymnaea

Aerial respiratory behavior in Lymnaea was operantly conditioned so that the animals perform aerial respiration significantly less often. Using the standard training procedure (pond water made hypoxic by bubbling N₂ through it) both food-deprived and fed animals learned and exhibited long-term memory (LTM). However, food-deprived animals exhibited neither learning nor memory when trained under a condition in which the hypoxic pond water also contained a food odorant (carrot, the food-odorant procedure). Fed animals, however, learned and exhibited LTM with the food-odorant procedure. Thus, the presence of the food odorant per se did not prevent learning or the establishment of LTM. Further experimentation, however, revealed that the ability of the snails to have recall (i.e., memory) for the learned behavior was dependent on the context in which memory was tested. That is, if animals were trained with the food-odorant procedure they could only exhibit recall if tested in the food-odorant context and vice versa with the standard training procedure. Thus, although fed animals could learn and show LTM with either training and testing procedure, LTM could only be seen when they were tested in the context in which they were trained.     

Inference suppression and semantic memory retrieval: Every counterexample counts

Reasoning with conditionals involving causal content is known to be affected by retrieval of counterexamples from semantic memory. In this study we examined the characteristics of this search process in everyday conditional reasoning. In Experiment 1 we manipulated the number (zero to four) of explicitly presented counterexamples (alternative causes or disabling conditions) for causal conditionals. In Experiment 2, using a generation pretest, we measured the number of counterexamples participants could retrieve for a set of causal conditionals. One month after the pretest, participants were presented a reasoning task with the same conditionals. The experiments indicated that acceptance of modus ponens linearly decreased with every additionally retrieved disabler, whereas affirmation of the consequent acceptance linearly decreased as a function of the number of retrieved alternatives. Results for denial of the antecedent and modus tollens were less clear. The findings show that the search process does not necessarily stop after retrieval of a single counterexample and that every additional counterexample has an impact on the inference acceptance.     

Similarity of encoding context does not influence resistance to memory impairment following misinformation

Several recent studies have shown that exposure to verbal misleading post-event information does not impair subjects' ability to retrieve originally seen details. Two experiments were conducted to test the hypothesis that subjects would be more susceptible to memory impairment if the original and misleading information were presented in similar contextual formats. The results showed that misleading information did not lead to memory impairment when both original and misleading information were presented in the context of slides (Experiment 1) or when both original and misleading information were presented in the context of narratives (Experiment 2). Furthermore, resistance to memory impairment was observed both at relatively low levels of memory for the original information (Experiment 1) and at relatively high levels of memory for the original information (Experiment 2). The implications of the present results for interference principles of forgetting are discussed.     

Olfactory context and memory retrieval in 3-month-old infants

Three experiments examineed whether olfactory stimuli can produce context-dependent effects in infant memory. In eash, 3-month-old infants learned to kick to control the movement of an overhead modile in the presence of an ambient odor. Retention was assessed 1, 3, or 5 days later. During the retention test, the olfactory context was either the same odor, a different odor, or “no odor.” At 1 day, infants exhibited retention when tested in the presence of the same odor. Infants in the no odor condition exhibited partial retention, whereas memory retrieval was completely disrupted for infants tested in the presence of the different odor. After the 3- and 5-day intervals, all groups showed forgetting. These results were not consistent with recent studies of 3-month-old infants trained and tested in the presence of a distinctive visual and auditory context. The findings suggest that olfactory stimuli are a silent feature of the environment for 3-month-old infants, but that they function as context cues in a way that differs from other sensory modalities.     

The role of retrieval mode and retrieval orientation in retrieval practice: insights from comparing recognition memory testing formats and restudying

The effectiveness of retrieval practice for aiding long-term memory, referred to as the testing effect, has been widely demonstrated. However, the specific neurocognitive mechanisms underlying this phenomenon remain unclear. In the present study, we sought to explore the role of pre-retrieval processes at initial testing on later recognition performance by using event-related potentials (ERPs). Subjects studied two lists of words (Chinese characters) and then performed a recognition task or a source memory task, or restudied the word lists. At the end of the experiment, subjects received a final recognition test based on the remember–know paradigm. Behaviorally, initial testing (active retrieval) enhanced memory retention relative to restudying (passive retrieval). The retrieval mode at initial testing was indexed by more positive-going ERPs for unstudied items in the active-retrieval tasks than in passive retrieval from 300 to 900 ms. Follow-up analyses showed that the magnitude of the early ERP retrieval mode effect (300–500 ms) was predictive of the behavioral testing effect later on. In addition, the ERPs for correctly rejected new items during initial testing differed between the two active-retrieval tasks from 500 to 900 ms, and this ERP retrieval orientation effect predicted differential behavioral testing gains between the two active-retrieval conditions. Our findings confirm that initial testing promotes later retrieval relative to restudying, and they further suggest that adopting pre-retrieval processing in the forms of retrieval mode and retrieval orientation might contribute to these memory enhancements.     

Specificity of learning through memory retrieval practice: The case of addition and subtraction

The identical elements (IE) model (Rickard, Healy, & Bourne, Learning, Memory, and Cognition 32:734–748, 1994) of fact representation predicts that, in both verbal and numerical domains, performance gains with retrieval practice on multielement items will be specific to the practiced stimulus–response combinations, failing to transfer even to altered stimulus–response mappings of practiced items. In the case of arithmetic, the model predicts no transfer across either complementary operations (e.g., 4 × 7 to 28 / 4) or complementary division or subtraction problems (e.g., 28 / 4 to 28 / 7). Although that model has successfully described transfer effects in the domains of multiplication–division and episodic cued recall, it is challenged by a recent demonstration of positive cross-operation transfer for addition and subtraction (Campbell & Agnew, Psychonomic Bulletin & Review 16:938–944, 2009). We report results of a new addition–subtraction transfer experiment, the design of which closely matched that of a prior multiplication–division experiment that supported the model. The transfer results were consistent with the IE model. A two-component model of memory retrieval practice effects is proposed to account for the discrepant experimental results for addition and subtraction and to guide future work.     

The dark side of testing memory: repeated retrieval can enhance eyewitness suggestibility

Eyewitnesses typically recount their experiences many times before trial. Such repeated retrieval can enhance memory retention of the witnessed event. However, recent studies (e.g., Chan, Thomas, & Bulevich, 2009) have found that initial retrieval can exacerbate eyewitness suggestibility to later misleading information--a finding termed retrieval-enhanced suggestibility (RES). Here we examined the influence of multiple retrieval attempts on eyewitness suggestibility to subsequent misinformation. In four experiments, we systematically varied the number of initial tests taken (between zero and six), the delay between initial testing and misinformation exposure (~30 min or 1 week), and whether initial testing was manipulated between- or within-subjects. University undergraduate students were used as participants. Overall, we found that eyewitness suggestibility increased as the number of initial tests increased, but this RES effect was qualified by the delay and by whether initial testing occurred in a within- or between-subjects manner. Specifically, the within-subjects RES effect was smaller than the between-subjects RES effect, possibly because of the influence of retrieval-induced forgetting/facilitation (Chan, 2009) when initial testing was manipulated within subjects. Moreover, consistent with the testing effect literature (Roediger & Karpicke, 2006), the benefits of repeated testing on later memory were stronger after a 1-week delay than after a 30-min delay, thus reducing the negative impact of RES in long-term situations. These findings suggest that conditions that are likely to occur in criminal investigations can either increase (repeated testing) or reduce (delay) the influence of RES, thus further demonstrating the complex relationship between eyewitness memory and repeated retrieval.     

The effect of a salient odor context on memory retrieval in young infants

Three-month-old infants were trained to move a mobile in the presence of a coconut or cherry odor (context). One or 5 days later, the infants were tested for retrieval in the presence of either the same odor, the alternate odor, or no odor. Infants tested with the training odor displayed retention at both intervals; retention was not seen at either interval in the alternate odor or no odor conditions. These data suggest that the odor combines with the mobile to form a compound-stimulus representation of the learned task whose presence after both short (1 day) and long (5 days) intervals is a necessary retrieval cue.     

Exploring the repetition paradox: The effects of learning context and massed repetition on memory

Although repetition is generally assumed to enhance the accessibility of memory for rehearsed material, recent research has suggested that prolonged repetition might actually be detrimental under some conditions. In the present work, we manipulated repetition duration and learning condition (intentional vs. incidental) in an effort to clarify the relationship between repetition and memory. Replicating previous findings, memory for repeated items declined with increased repetition under incidental-learning conditions. However, increased repetition had the opposite effect under intentional-learning conditions. Taken together, these results provide evidence for distinctive mechanisms of memory acquisition during repetition that vary depending on learning context.     

Effect of neonatal handling on adult rat spatial learning and memory following acute stress

Brief neonatal handling permanently alters hypothalamic-pituitary-adrenal axis function resulting in increased ability to cope with stress. Since stress is known to affect cognitive abilities, in the present study we investigated the effect of brief (15 min) handling on learning and memory in the Morris water maze, following exposure to an acute restraint stress either before training or recall. Exposure of non-handled rats to the acute stress prior to training resulted in quicker learning of the task, than in the absence of the stressor. When acute stress preceded acquisition, male handled rats showed an overall better learning performance, and both sexes of handled animals were less impaired in the subsequent memory trial, compared to the respective non-handled. In addition, the number of neurons immunoreactive for GR was higher in all areas of Ammon's horn of the handled rats during the recall. In contrast, the number of neurons immunoreactive for MR was higher in the CA1 and CA2 areas of the non-handled males. When the acute restraint stress was applied prior to the memory test, neonatal handling was not effective in preventing mnemonic impairment, as all animal groups showed a similar deficit in recall. In this case, no difference between handled and non-handled rats was observed in the number of GR positive neurons in the CA2 and CA3 hippocampal areas during the memory test. These results indicate that early experience interacts with sex and acute stress exposure in adulthood to affect performance in the water maze. Hippocampal corticosterone receptors may play a role in determining the final outcome.     

Timing matters: Temporal dynamics of stress effects on memory retrieval

Stress may impair memory retrieval. This retrieval impairment has been attributed to the action of the stress hormone cortisol, which is released with a delay of several minutes after a stressful encounter. Hence, most studies tested memory retrieval 20–30 min after stress, when the stress-induced cortisol increase peaks. In the present experiment, we investigated whether retrieval impairments can also be found at later intervals after stress. To this end, participants learned a list of words on day 1. Twenty-four hours later, they were first exposed to a stressor or a nonstressful control manipulation and completed a recognition test for the words either immediately thereafter, 25 min later, or 90 min later. Our findings showed that stress did not impair memory retrieval when memory was tested immediately after the stressor, before cortisol levels were elevated. However, retrieval performance was impaired 25 min after stress, when cortisol levels peaked, as well as 90 min after the stressor, when cortisol levels had already returned to baseline. The retrieval impairment 90 min after stress appeared to be even stronger than the one after 25 min. These findings suggest that the detrimental effects of stress on retrieval performance may last longer than is usually assumed.     

Psychosocial stress impairs working memory at high loads: an association with cortisol levels and memory retrieval

Stress and cortisol are known to impair memory retrieval of well-consolidated declarative material. The effects of cortisol on memory retrieval may in particular be due to glucocorticoid (GC) receptors in the hippocampus and prefrontal cortex (PFC). Therefore, effects of stress and cortisol should be observable on both hippocampal-dependent declarative memory retrieval and PFC-dependent working memory (WM). In the present study, it was tested whether psychosocial stress would impair both WM and memory retrieval in 20 young healthy men. In addition, the association between cortisol levels and cognitive performance was assessed. It was found that stress impaired WM at high loads, but not at low loads in a Sternberg paradigm. High cortisol levels at the time of testing were associated with slow WM performance at high loads, and with impaired recall of moderately emotional, but not of highly emotional paragraphs. Furthermore, performance at high WM loads was associated with memory retrieval. These data extend previous results of pharmacological studies in finding WM impairments after acute stress at high workloads and cortisol-related retrieval impairments.     

Context retrieval and context change in free recall: recalling from long-term memory drives list isolation

Three experiments used the "list-before-the-last" free recall paradigm (Shiffrin, 1970) to investigate retrieval for context and the manner in which context changes. This paradigm manipulates target and intervening list lengths to measure the interference from each list, providing a measure of list isolation. Correct target list recall was only affected by the target list length when participants engaged in recall between the lists, whereas there were effects of both list lengths with other activities. This suggests that the act of recalling drives context change, thus isolating the target list from interference. Correspondingly, incorrect recall of intervening list items was affected only by the length of the intervening list when recall occurred between the lists, but was otherwise affected by both list lengths. Concurrent with these changes in context similarity, there were apparent changes in context retrieval, as indicated by the overall levels of target retrieval versus intervening recall. A multinomial model of sampling and recovery was implemented to assess the adequacy of this account and to quantify context similarity and context retrieval.     

The dual effect of context on memory of related and unrelated themes: Discrimination at encoding and cue at retrieval

The influence of contextual factors on encoding and retrieval in recognition memory was investigated using a retroactive interference paradigm. Participants were randomly assigned to four context conditions constructed by manipulating types of presentation modality (pictures vs words) for study, interference, and test stages, respectively (ABA, ABB, AAA, & AAB). In Experiment 1 we presented unrelated items in the study and interference stages, while in Experiment 2 each stage contained items from the same semantic category. The results demonstrate a dual role for context in memory processes-at encoding as well as at retrieval. In Experiment 1 there is a hierarchical order between the four context conditions, depending on both target-test and target-interference contextual similarity. Adding a categorical context in Experiment 2 helped to specify each list and therefore better distinguish between target and interferer information, and in some conditions compensated for their perceptual similarity.     

Absolute pitch memory: Its prevalence among musicians and dependence on the testing context

Absolute pitch (AP) is widely believed to be a rare ability possessed by only a small group of gifted and special individuals (AP possessors). While AP has fascinated psychologists, neuroscientists, and musicians for more than a century, no theory can satisfactorily explain why this ability is so rare and difficult to learn. Here, we show that AP ability appears rare because of the methodological issues of the standard pitch-naming test. Specifically, the standard test unnecessarily poses a high decisional demand on AP judgments and uses a testing context that is highly inconsistent with one’s musical training. These extra cognitive challenges are not central to AP memory per se and have thus led to consistent underestimation of AP ability in the population. Using the standard test, we replicated the typical findings that the accuracy for general violinists was low (12.38 %; chance level = 0 %). With identical stimuli, scoring criteria, and participants, violinists attained 25 % accuracy in a pitch verification test in which the decisional demand of AP judgment was reduced. When the testing context was increasingly similar to their musical experience, verification accuracy improved further and reached 39 %, three times higher than that for the standard test. Results were replicated with a separate group of pianists. Our findings challenge current theories about AP and suggest that the prevalence of AP among musicians has been highly underestimated in prior work. A multimodal framework is proposed to better explain AP memory.     

Effects of retrieval practice and presentation modality on verbal learning: testing the limits of the testing effect

ABSTRACT

The testing effect refers to improved memory after retrieval practice and has been researched primarily with visual stimuli. In two experiments, we investigated whether the testing effect can be replicated when the to-be-learned information is presented auditorily, or visually?+?auditorily. Participants learned Swahili-English word pairs in one of three presentation modalities – visual, auditory, or visual?+?auditory. This was manipulated between-participants in Experiment 1 and within-participants in Experiment2. All participants studied the word pairs during three study trials. Half of participants practiced recalling the English translations in response to the Swahili cue word twice before the final test whereas the other half simply studied the word pairs twice more. Results indicated an improvement in final test performance in the repeated test condition, but only in the visual presentation modality (Experiments 1 and 2) and in the visual?+?auditory presentation modality (Experiment 2). This suggests that the benefits of practiced retrieval may be limited to information presented in a visual modality.     

The influence of learning methods on collaboration: prior repeated retrieval enhances retrieval organization, abolishes collaborative inhibition, and promotes post-collaborative memory

Research on collaborative memory has unveiled the counterintuitive yet robust phenomenon that collaboration impairs group recall. A candidate explanation for this collaborative inhibition effect is the disruption of people's idiosyncratic retrieval strategies during collaboration, and it is hypothesized that employing methods that improve one's organization protects against retrieval disruption. Here it is investigated how one's learning method during the study phase--defined as either repeatedly studying or repeatedly retrieving information--influences retrieval organization and what effects this has on collaborative recall and post-collaborative individual recall. Results show that repeated retrieval consistently eliminated collaborative inhibition. This enabled participants to gain the most from re-exposure to materials recalled by their partners that they themselves did not recall and led to improvements in their individual memory following collaboration. This repeated retrieval advantage stemmed from the preferential manner in which this learning method strengthened retrieval organization. Findings are also discussed that reveal a relationship between retrieval organization and the interaction observed between learning method and short versus long delay seen in the testing effect literature. Finally, results show that the elusive benefits of cross-cuing during collaboration may be best detected with a longer study-test delay. Together, these findings illuminate when and how collaboration can enhance memory.     

The effects of cortisol increase on long-term memory retrieval during and after acute psychosocial stress

In this study the effects of stress-induced cortisol increases on long-term memory retrieval during and after acute psychosocial stress were examined. Seventy male students were exposed to either a psychosocial stress task or to a non-stressful control task. During and after this task, retrieval was tested for idiosyncratic emotionally negative and neutral word pair associations that were learned 1 day or 5 weeks earlier. Within the stress condition, retrieval of negative words, 5 weeks after learning, was impaired both during and after the stress task compared to the control group. Further, during the stress task, when sympathetic activity was enhanced, impaired retrieval of both neutral and emotional words was significantly related to enhanced cortisol response. In contrast, after the stress task, when cortisol levels were still increased but sympathetic activity was low again, no association was found between cortisol increase and retrieval of either neutral or emotional material. These results are in line with the previous animal research showing that when arousal is high, cortisol increase can impair memory retrieval.     

Dissociated verbal and nonverbal retrieval and learning following left anterior temporal damage

A subject with circumscribed damage to mesial and nonmesial left anterior temporal structures (which included the left entorhinal cortex and hippocampus and the left anterolateral association cortices) maintains accurate nonverbal records of past experiences, and acquires accurate new nonverbal records. However, he has a severe defect in the retrieval and acquisition of specific verbal tags denoting those records. This dissociation is revealed by standard neuropsychological tasks, and by experimental probes focused on (1) retrieval of previously learned verbal and nonverbal entities; and (2) acquisition of new visuoverbal relationships. The results extend our current understanding of the manner in which mesial and nonmesial structures in the anterior temporal lobe contribute to the formation and storage of verbal and nonverbal records.