The effect of constant vs. varied encoding and massed vs. distributed presentations on recall of paired associates

The variables of coding (constant vs. varied) and spacing (massed vs. distributed) were factorially combined in an independent-groups design. Sixteen nominal pairs were presented twice, with the two presentations being either massed or distributed. A given nominal pair (e.g., AR-LE) was accompanied either by the same word-pair code on both presentations (e.g.,arm-leg) or by a different code on each presentation (e.g.,arm-leg; arrive-leave). On a subsequent recall test, the nominal stimulus only was shown. Better recall of the nominal response was found after constant coding and after distributed presentations, and there was no interaction between the spacing and coding variables. The results (a) support none of the current proposed explanations for the distributed practice effect, and (b) suggest that the critical factor in determining the probability of response recall is the strength of the strongest potential route to the response, not the number of different routes. This research was supported by a grant from the Graduate School of the University of Wisconsin.     

Novelty assessment in the brain and long-term memory encoding

Recent positron emission tomography (PET) studies have identified neuronal components of widespread novelty-assessment networks in the brain. We propose that the efficacy of encoding on-line information into long-term memory depends on the novelty of the information as determined by these networks, and report a test of this “novelty/encoding” hypothesis. Subjects studied a list of words. Half of the words were “familiar” by virtue of their repeated presentation to the subjects before the study of the critical list; the other half were novel, in that they had not previously been encountered in the experiment. The results conformed to the prediction of the novelty/encoding hypothesis: accuracy of explicit (episodic) recognition was higher for novel than for familiar words.     

No evidence for a role of reconsolidation in updating of paired associates

Reconsolidation theory states that memories are labilized through reactivation, making them prone to change, before being re-consolidated. When information in memory requires updating, reconsolidation theory therefore predicts that reminders of previously learned information should facilitate updating of that information and should thus improve memory for the updated information. In two experiments, we tested this prediction by investigating memory for word pairs over a short time-scale. Participants studied word pairs (A–B), some of which were subsequently updated with word pairs that shared the first word (A–C). Half of the A–C pairs received a pre-study reminder of the first word in the pair so as to reactivate and labilize A–B memory. In a recognition memory test targeting the A–C list, reminders by and large had no effect on memory. Results thus failed to support the predictions of reconsolidation theory.     

Prior knowledge and memory: the episodic encoding of implicitly activated associates and rhymes

The presentation of a familiar word activates related concepts, and, once encoded, related concepts interfere with memory for the work actually presented. Presented words that activate larger numbers of related concepts are generally more difficult to recall than those that activate smaller numbers. The purpose of the present experiments was to explore the effects of study-trial orientation and test delay on the encoding of both rhyme- and meaning-related concepts. The results of Experiments 1 and 2 indicate that meaning-related concepts are encoded and interfere with memory for the presented target regardless of study-trial orientation. Interference is obtained even when the study-trial context emphasizes phonemic information and subjects are incidentally oriented to rating rhyme properties. However, this interference effect disappears when the test trial is delayed. In contrast, the results of Experiments 1-4 indicate that rhyme-related concepts are encoded and interfere with memory for the presented target only when subjects explicitly attend to the rhyme dimension. Once oriented, this interference effect is found after a relatively long delay. These differences are attributed to differences in attentional processing. The encoding of meaning-related concepts results from relatively automatic processes and the encoding of rhyme-related concepts requires subjects to attend to rhyme.     

The neuroimaging of long-term memory encoding processes

There needs to be more crosstalk between the lesion and functional neuroimaging memory literatures. This is illustrated by a discussion of episode and fact encoding. The lesion literature suggests several hypotheses about which brain regions underlie the storage of episode and fact information, which can be explored by functional neuroimaging. These hypotheses have been underexplored because neuroimaging studies of encoding have been insufficiently hypothesis-driven and have not controlled encoding-related processes sufficiently well to allow clear interpretations of results to be made. Nevertheless, there is good evidence that certain kinds of associative encoding and/or consolidation are sufficient to activate the medial temporal lobes, and preliminary evidence that some kinds of associative priming may reduce activation of this region. It remains to be proved that attentional orienting to certain kinds of novel information activates the medial temporal lobes. Evidence is growing that the HERA model, developed from neuroimaging rather than lesion data, requires modification and that frontal cortex encoding activations are probably caused by executive processes that are important in effortful memory processing. Neuroimaging studies allow the detection of encoding-related activations in previously unexpected brain regions (e.g. parietal lobes) and, in turn, these findings can be explored with lesion studies.     

Pictorial encoding reduces false recognition of semantic associates

High levels of false recognition can be observed after people study lists of semantic associates that all converge on a nonpresented lure word. To test the idea that encoding distinctive perceptual information would help to reduce false recognition, we presented a line drawing representing each associated word during study list presentation and later tested recognition of studied words and lure words. Two experiments revealed marked reductions in false recognition after pictorial encoding, relative after to word encoding. Results suggest that people reject related and unrelated lures because these items lack the distinctive qualities associated with remembered pictures.     

The benefit of surface uniformity for encoding boundary features in visual working memory

Using a change detection paradigm, the present study examined an object-based encoding benefit in visual working memory (VWM) for two boundary features (two orientations in Experiments 1-2 and two shapes in Experiments 3-4) assigned to a single object. Participants remembered more boundary features when they were conjoined into a single object of uniform color than when they were not bound together into an object. However, such an object-based benefit diminished or disappeared when those features occurred on different parts of an object, as defined by surface discontinuity or by negative minima of curvature. These results suggest that the number of boundary features that can be stored in VWM is influenced by the hierarchical structure of objects: surface uniformity facilitates the integration of two boundary features into a single object representation, but this integration is weakened when the features occur on different parts of an object.