The Role of Visual Representations within Working Memory for Paired-Associate and Serial Order of Spoken Words

Backward recall and foreknowledge of recall direction: a test of the Encoding-Retrieval Matching Hypothesis

When participants must recall a sequence of items in reverse order just after their presentation, inconsistent findings have been observed relative to when participants must recall a sequence in their presentation order. Recently, the Encoding-Retrieval Matching Hypothesis (ERM) has been developed to account for these inconsistencies. Within the ERM hypothesis, foreknowledge of recall direction plays an important role. In two experiments, we tested a key prediction of the ERM hypothesis: In backward recall with foreknowledge of recall direction, the size of the effect will vary as a function of its reliance on visuospatial representations. Participants performed an immediate serial recall task with digits. As predicted, the detrimental effect of manual-spatial tapping was larger in backward recall relative to forward recall when recall direction was predictable (Experiment 1b), but not when it was unpredictable (Experiment 1a). In Experiment 2, the word length effect, not relying on visuospatial representations, was equally large in forward and backward recall, and it was unaffected by foreknowledge of recall direction. Overall, the results support the predictions derived from the ERM hypothesis and contribute to the delineation of when and how foreknowledge can influence backward recall performance relative to forward recall performance.

Imagery-based strategies for memory for associations

Cued recall of word pairs is improved by asking participants to combine items in an interactive image. Meanwhile, interactive images facilitate serial-recall (Link Method), but even better when each item is imagined alongside a previously learned peg-word (Peg List Method). We asked if a peg system could support memory for pairs, hypothesising it would outperform interactive imagery. Tested with cued recall, five study strategies were manipulated between-subjects, across two experiments: (1) Both words linked to one peg; (2) Each word linked to a different peg; (3) Peg list method but studying as a serial list; (4) Interactive imagery (within-pairs); (5) Link Method. Participants were able to apply peg-list strategies to pairs, as anticipated by mathematical modelling. Error-patterns spoke to mathematical models; peg lists exhibited distance-based confusability, characteristic of positional-coding models, and errors tended to preserve within-pair position, even for inter-item associative strategies, suggesting models of association should incorporate position. However, the peg list strategies came with a speed-accuracy tradeoff and did not challenge the superiority of the interactive imagery strategy. Without extensive practice with peg list strategies, interactive imagery remains superior for associations. Peg strategies may excel instead in tasks that primarily test serial order or with extensive training.

Dynamic Visual Noise Does Not Affect Memory for Fonts

Dynamic visual noise (DVN) selectively impairs memory for some types of stimuli (e.g., colors, textures, concrete words), but not for others (e.g., matrices, Chinese characters, simple shapes). According to the image definition hypothesis, the key difference is whether the stimulus leads to images that are ill-defined or well-defined. The former will be affected because the addition of noise quickly reduces the usefulness of the image in supplying information about the item's identity. The image definition hypothesis predicts that fonts should lead to ill-defined images and therefore should be affected by DVN, and although three previous studies appear to show this result, they lack a key control condition and report only proportion correct. Two experiments reassessed whether DVN affects memory for fonts, but, unlike the previous studies, both included a static visual noise condition and both were analyzed using signal detection measures. There was no evidence that DVN affected memory for font information, thus disconfirming a prediction of the original version of image definition hypothesis. We suggest a revised version that focuses on redintegration can explain the results.

Dynamic visual noise affects ill-defined, not well-defined, images

Dynamic visual noise (DVN), a matrix of squares that randomly alternate between black and white, interferes with some but not all tasks that involve visuo-spatial processing. Although visual working memory is generally invoked to explain the detrimental effects of DVN, the failure of DVN to impair memory for some stimuli that should be processed via visual working memory has not been satisfactorily explained. The image-definition hypothesis proposes that DVN will impair only ill-defined, not well-defined, images. We report five experiments that test this hypothesis. Experiments 1 and 2 use stimuli that lead to well-defined visual images (matrices, photographs of common objects) and no effect of DVN was observed. In contrast, Experiments 3 and 4 use stimuli that lead to ill-defined visual images (textures, photographs of snowflakes) and DVN affected performance. Experiment 5 demonstrated that a potentially disconfirmatory result in the literature was due to analysing proportion correct rather than a measure of discriminability. These results offer initial support for the image-definition hypothesis, and we discuss the implications for theories explaining DVN.

Visual similarity effects in immediate serial recall and (sometimes) in immediate serial recognition

Words that sound dissimilar are recalled better than otherwise comparable words that sound similar on both immediate serial recall and immediate serial recognition tests, the so-called acoustic similarity effect. Although studies using immediate serial recall have shown an analogous visual similarity effect, in which words that look dissimilar are recalled better than words that look similar, this effect has not been examined in immediate serial recognition. We derived a prediction from the Feature Model that a visual similarity effect will be observed in immediate serial recognition only when the items are acoustically dissimilar; the model predicts no effect when the items are acoustically similar. Experiments 1 and 2 used visually dissimilar and visually similar stimuli that were all acoustically similar and replicated the visual similarity effect in serial recall but revealed no effect in serial recognition. Experiments 3 and 4 used a second set of stimuli that were acoustically dissimilar and found a visual similarity effect in both serial recall and serial recognition. The experiments confirm the Feature Model's predictions and add to earlier findings that the two tests, serial recall and serial recognition, may show quite different results because the two tests are not as similar as previously thought.

Multiple high-reward items can be prioritized in working memory but with greater vulnerability to interference

Emerging literature indicates that working memory and attention interact in determining what is retained over time, though the nature of this relationship and the impacts on performance across different task contexts remain to be mapped. In the present study, four experiments examined whether participants can prioritize one or more high-reward items within a four-item target array for the purposes of an immediate cued recall task, and the extent to which this mediates the disruptive impact of a postdisplay to-be-ignored suffix. All four experiments indicated that endogenous direction of attention toward high-reward items results in their improved recall. Furthermore, increasing the number of high-reward items from one to three (Experiments 1-3) produces no decline in recall performance for those items, while associating each item in an array with a different reward value results in correspondingly graded levels of recall performance (Experiment 4). These results suggest the ability to exert precise voluntary control in the prioritization of multiple targets. However, in line with recent outcomes drawn from serial visual memory, this endogenously driven focus on high-reward items results in greater susceptibility to exogenous suffix interference, relative to low-reward items. This contrasts with outcomes from cueing paradigms, indicating that different methods of attentional direction may not always result in equivalent outcomes on working memory performance.

The (lack of) effect of dynamic visual noise on the concreteness effect in short-term memory

It has been suggested that the concreteness effect in short-term memory (STM) is a consequence of concrete words having more distinctive and richer semantic representations. The generation and storage of visual codes in STM could also play a crucial role on the effect because concrete words are more imaginable than abstract words. If this were the case, the introduction of a visual interference task would be expected to disrupt recall of concrete words. A Dynamic Visual Noise (DVN) display, which has been proven to eliminate the concreteness effect on long-term memory (LTM), was presented along encoding of concrete and abstract words in a STM serial recall task. Results showed a main effect of word type, with more item errors in abstract words, a main effect of DVN, which impaired global performance due to more order errors, but no interaction, suggesting that DVN did not have any impact on the concreteness effect. These findings are discussed in terms of LTM participation through redintegration processes and in terms of the language-based models of verbal STM.