Prior knowledge: the effects of natural category size on memory for implicitly encoded concepts

Studying a familiar word activates its associates, and these associates affect the likelihood of recalling the studied word in a cued recall task. These experiments examined variables that normally affect memory for the studied word to determine if they have similar effects on memory for the word's associates. Memory for associates was tested by cued recall (Experiments 1-3) or by recognition (Experiments 4-5), with the number and strength of the associates varied in all experiments. In different experiments, test instructions (direct-indirect), distractor tasks, lag, and amount of practice were manipulated. Provided that subjects were not distracted prior to test, the probability of recalling associates of the studied word decreased with the number of associates activated and with their strength under all conditions. The strength of the associates but not their number affected recognition. In general, variables that affected recall and recognition of studied words had parallel effects on their associates.     

Sentence encoding and implicitly activated memories

Some words have fewer direct associates than others, and, when words varying in set size are studied in a list-learning task, those with smaller sets are more likely to be recalled. This set-size effect is found in cued recall when the words are studied in the absence of related words, but not when studied in the presence of related words. Related words provide context and theoretically inhibit irrelevant associates. The present research determined that set-size effects are found when words are encoded in sentence contexts. In contrast to list-learning experiments, the results of three experiments found such effects even when lexically related words were present in the sentences. Other findings indicated that target-set-size effects were determined by the proximity of related words in the sentence and the nature of the test cue. The results are discussed in relation to a model for explaining set-size effects and to selective findings from the sentence-comprehension literature.     

Cognitive neuroscience of episodic memory encoding

This paper presents a cognitive neuroscientific perspective on how human episodic memories are formed. Convergent evidence from multiple brain imaging studies using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) suggests a role for frontal cortex in episodic memory encoding. Activity levels within frontal cortex can predict episodic memory encoding across a wide range of behavioral manipulations known to influence memory performance, such as those present during levels of processing and divided attention manipulations. Activity levels within specific frontal and medial temporal regions can even predict, on an item by item basis, whether an episodic memory is likely to form. Furthermore, separate frontal regions appear to participate in supplying code-specific information, including distinct regions which process semantic attributes of verbal information as well as right-lateralized regions which process nonverbal information. We hypothesize that activity within these multiple frontal regions provides a functional influence (input) to medical temporal regions that bind the information together into a lasting episodic memory trace.     

Distinguishing the neural correlates of episodic memory encoding and semantic memory retrieval

Episodic memory and semantic memory interact very closely. In particular, episodic memory encoding (EE) tends to elicit semantic memory retrieval (SR), and vice versa. Thus, similar activations for EE and SR in functional neuroimaging studies may reflect shared memory processes, or they may reflect the fact that EE and SR are usually confounded. To address this issue, we used a factorial functional magnetic resonance imaging approach to disentangle the neural correlates of EE and SR. Within the left temporal lobe, the hippocampus was associated with successful EE, whereas a posterior lateral region was associated with successful SR. Within the left inferior prefrontal cortex, a posterior region was involved in SR, a mid region was involved in both SR and EE, and an anterior region was involved in EE, but only when SR was also high. Thus, the neural correlates of EE and SR are dissociable but interact in specific brain regions.     

Variation in working memory capacity and episodic memory: Examining the importance of encoding specificity

In the present study, we examined the extent to which encoding specificity influences the relation between individual differences in working memory capacity (WMC) and episodic recall. Participants performed a paired associates cued recall task in which a rhyme or a semantic judgment was made during encoding. During recall participants were presented with the cue word along with either a rhyme or semantic cue. Across both rhyme and semantic conditions, encoding and retrieval conditions either matched or mismatched. When encoding and retrieval conditions matched, high WMC individuals outperformed low WMC individuals. When encoding and retrieval conditions mismatched, high and low WMC individuals performed equivalently. Importantly, this occurred because high WMC individuals were hurt more than low WMC individuals when conditions mismatched. These results demonstrate the importance of encoding specificity in the relation between WMC and episodic recall as well as of unifying prior work that has demonstrated that high WMC individuals are hurt more in some recall conditions than are low WMC individuals.     

How implicitly activated and explicitly acquired knowledge contribute to the effectiveness of retrieval cues

The extralist cued recall task simulates everyday reminding because a memory is encoded on the fly and retrieved later by an unexpected cue. Target words are studied individually, and recall is cued by associatively related words having preexisting forward links to them. In Experiments 1 and 2, forward cue-to-target and backward target-to-cue strengths were varied over an extended range in order to determine how these two sources of strength are related and which source has a greater effect. Forward and backward strengths had additive effects on recall, with forward strength having a consistently larger effect. The PIER2 model accurately predicted these findings, but a plausible generation-recognition version of the model, called PIER.GR, could not. In Experiment 3, forward and backward strengths, level of processing, and study time were varied in order to determine how preexisting lexical knowledge is related to knowledge acquired during the study episode. The main finding indicates that preexisting knowledge and episodic knowledge have additive effects on extralist cued recall. PIER2 can explain these findings because it assumes that these sources of strength contribute independently to recall, whereas the eSAM model cannot explain the findings because it assumes that the sources of strength are multiplicatively related.     

Narrative organisation at encoding facilitated children's long-term episodic memory

This study examined the effect of narrative organisation at encoding on long-term episodic memory in a sample of five- to seven-year-old children (N = 113). At an initial interview, children were asked to narrate a story from a picture book. Six months later, they were interviewed again and asked to recall the story and answer a series of direct questions about the story. Children who initially encoded more information in narrative and produced more complete, complex, cohesive and coherent narratives remembered the story in greater detail and accuracy following the six-month interval, independent of age and verbal skills. The relation between narrative organisation and memory was consistent across culture and gender. These findings provide new insight into the critical role of narrative in episodic memory.     

The effects of prior knowledge on the encoding of episodic contextual details

A positive relationship between prior knowledge and item memory is a consistent finding in the literature. In the present study, we sought to determine whether this relationship extends to episodic details that are present at the time of encoding, namely source memory. Using a novel experimental design, we were able to show both between- and within-subjects effects of prior knowledge on source memory. Specifically, the results revealed that the degree of prior knowledge positively predicted memory for source specifying contextual details. In addition, by including two conditions in which attention was divided either at encoding or retrieval, we were able to show that prior knowledge influences memory by affecting encoding processes. Overall, the data suggest that a priori knowledge within a specific domain allows attentional resources to be allocated toward the encoding of contextual details.     

The assessment of discriminative encoding in memory for paired associates

A technique for providing for the measurement of encoding stability and intralist stimulus discrimination is presented and applied to the analysis of some paired-associate data. Essentially, the measure involves a recall test for all stimuli in the list except one, then presenting either a previously tested stimulus or the missing stimulus. Recognition of repeated stimuli reflects code stability, and recognition of the missing stimulus reflects stimulus discrimination.     

Framing pictures: the role of knowledge in automatized encoding and memory for gist

In general, frame theories are theories about the representation and use of knowledge for pattern recognition. In the present article, the general properties of frame theories are discussed with regard to their implications for psychological processes, and an experiment is presented which tests whether this approach yields viable predictions about the manner in which people comprehend and remember pictures of real-world scenes. Normative ratings were used to construct six target pictures, each of which contained both expected and unexpected objects. Eye movements were then recorded as subjects who anticipated a difficult recognition test viewed the targets for 30 sec each. Then, the subjects were asked to discriminate the target pictures from distractors in which either expected or unexpected objects had been changed. One consequence of the embeddedness of frame systems is that global frames may function as "semantic pattern detectors," so that the perceptual knowledge in them could be used for relatively automatic pattern recognition and comprehension. Thus, subjects might be able to identify expected objects by using automatized encoding procedures that operate on global physical features. In contrast, identification of unexpected objects (i.e., objects not represented in the currently active frame) should generally require more analysis of local visual details. These hypotheses were confirmed with the fixation duration data: First fixations to the unexpected objects were approximately twice as long as first fixations to the expected objects. On the recognition test, subjects generally noticed only the changes that had been made to the unexpected objects, despite the fact that the proportions of correct rejections were made conditional on whether the target objects had been fixated. These data are again consistent with the idea that local visual details of objects represented in the frame are not neccesary for identification and are thus not generally encoded. Further, since subjects usually did not notice when expected objects were deleted or replaced with different expected objects, it was concluded that if two events instantiate the same frame, they may often be indistinguishable, as long as any differences between them are represented as arguments in the frame. Thus, for the most part, the only information about an event that is episodically "tagged" is information which distinguishes that particular event from others of the same general class. The data reinforce the utility of a frame theory approach to perception and memory.     

Variation in working memory capacity and episodic recall: The contributions of strategic encoding and contextual retrieval

The present study examined the extent to which differences in strategic encoding and contextual retrieval account for the relation between individual differences in working memory capacity (WMC) and variation in episodic recall. Participants performed a continual distractor task under either incidental- or intentional-encoding conditions. High-WMC individuals outperformed low-WMC individuals across both encoding conditions and, notably, to a greater degree in the intentional-encoding condition. These results suggest that WMC differences in episodic recall are likely due to a combination of differences in both contextual-retrieval and strategic-encoding processes. These findings are consistent with prior work showing that high-WMC individuals are better at engaging in strategic-encoding processes during the presentation of items than are low-WMC individuals and are better at using contextual cues to focus the search on correct items during retrieval.     

Prior knowledge and memory: the influence of natural category size as a function of intention and distraction

Words having larger numbers of related associates are more difficult to recall under conditions of intentional learning. This finding indicates that memory performance is inversely related to natural category size. The purpose of the experiments presented in this article was to evaluate the potential influence of orienting task and attention shifts associated with delayed testing on the natural category size effect. The results of Experiments 1 and 2 indicate that it is obtained regardless of task orientation. However, the results of Experiments 2 and 3 indicate that the effect is easily disrupted. Even after only 5 min of solving multiplication problems, words having larger sets of associates are no more difficult to recall than those having smaller sets. These findings suggest that related associates are automatically activated and encoded whenever a familiar concept is experienced in the absence of specific semantic cues. However, words having larger sets will be more difficult to recall only when these related associates are in a state of current activation.     

Organization in visual episodic memory: relationships between verbalized knowledge, strategy use, and performance

Relationships between verbalized knowledge (metamemory), strategy use, and performance were examined in a memory task for visually presented episodes. Kindergarten, second-grade, and fifth-grade students were asked to reconstruct a sequence of pictures forming an episode from an array of original pictures and foils. The episodes varied on two dimensions; materials type and the logic of the sequence. Materials were either typical (familiar animal characters and scenes) or atypical (geometric figures) story materials. Sequences either readily conveyed a story (logical) or were rearranged to present a random ordering of pictures (illogical). Children were questioned about their use of a story line to help remember the picture sequences (general questioning) and were asked more specific questions concerning the reasons for their picture selection during the task (specific questioning). Children at all ages recalled logical sequences better than illogical ones. Second- and fifth-grade children recalled animal episodes better than geometric form episodes. Children at all ages showed a correspondence between strategy use and metamemory as assessed by verbalization of relationships among pictures during the specific questioning. However, when the more typical general question format was used to assess metamemory, strategy use preceded verbalized knowledge of strategy use.     

Prior knowledge and recognition

The purpose of this series of experiments was to determine if and when word recognition would depend on the number of related concepts represented in permanent memory. Words defining either large or small rhyme or meaning categories were studied and tested under various conditions. The results indicated that rhyme category size influenced recognition whenever rhyme was emphasized during both study and testing phases. Words belonging to larger rhyme sets were not recognized as well as those belonging to smaller rhyme sets. In contrast, meaning-related set size had no effect on recognition. These and other findings indicate that the breadth of prior knowledge can influence recognition but only under limited conditions that reactivate this knowledge at test.     

Retrieval processing and episodic memory

The emergence of brain imaging has had a major impact on research into the cognitive and neural bases of human memory. An area in which this impact has been particularly strong is retrieval processing - the processes engaged when attempting to retrieve information during a memory test. Several different classes of retrieval process - such as 'mode', 'effort' and 'success' - have been invoked to account for findings from neuroimaging studies of episodic retrieval. In this article we discuss how these different kinds of process, along with a fourth kind associated with 'retrieval orientation', can be investigated in brain imaging experiments. We then review studies of retrieval processing, and assess how well their designs match up to our proposed criteria for dissociating the neural correlates of different classes of retrieval process. We conclude that few studies have used designs that permit these different kinds of process to be independently identified, and that presently there is little evidence to indicate which kinds of processing can be fractionated in terms of their neural correlates.     

The role of episodic and semantic memory in episodic foresight

In this paper we describe a special form of future thinking, termed “episodic foresight” and its relation with episodic and semantic memory. We outline the methodologies that have largely been developed in the last five years to assess this capacity in young children and non-human animals. Drawing on Tulving's definition of episodic and semantic memory, we provide a critical analysis of the role that both types of memory might have on the episodic foresight tasks described in the literature. We conclude by highlighting some unanswered questions and suggesting future directions for research that could further our understanding of how memory is intimately connected to episodic foresight.     

Working memory in spatial knowledge acquisition: Differences in encoding processes and sense of direction

This study examined how different components of working memory are involved in spatial knowledge acquisition for good and poor sense‐of‐direction (SOD) people. We employed a dual‐task method, and asked participants to learn routes from videos with verbal, visual and spatial interference tasks and without any interference. Results showed that participants with a good SOD encoded landmarks and routes verbally and spatially, and integrated knowledge about them into survey knowledge with the support of all three components of working memory. In contrast, participants with a poor SOD encoded landmarks only verbally, and tended to rely on the visual component of working memory in the processing of route knowledge. Based on the results, a possible model for explaining the differences in spatial knowledge acquisition and SOD was proposed. Copyright © 2010 John Wiley & Sons, Ltd.     

Prior knowledge and exemplar frequency

New concepts can be learned by statistical associations, as well as by relevant existing knowledge. We examined the interaction of these two processes by manipulating exemplar frequency and thematic knowledge and considering their interaction through computational modeling. Exemplar frequency affects category learning, with high-frequency items learned more quickly than low-frequency items, and prior knowledge usually speeds category learning. In two experiments in which both of these factors were manipulated, we found that the effects of frequency are greatly reduced when stimulus features are linked by thematic prior knowledge and that frequency effects on single stimulus features can actually be reversed by knowledge. We account for these results with the knowledge resonance model of category learning (Rehder & Murphy, 2003) and conclude that prior knowledge may change representations so that empirical effects, such as those caused by frequency manipulations, are modulated.