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There is a recent surge of interest in maintenance processes in working memory, such as articulatory rehearsal, elaboration, and attentional refreshing. Yet, we know little about the central attentional demand of these processes. It has been assumed that articulatory rehearsal does not require central attention at all (Vergauwe, Camos, & Barrouillet, 2014), being in essence a cost-free strategy. In contrast, elaboration and attentional refreshing are assumed to incur large and continuous costs on central attention. We tested these assumptions in three experiments in which participants were presented with a varying number of words to rehearse. Participants were instructed to rehearse the words aloud, or to elaborate them by creating interactive images. Attentional refreshing was examined in a condition in which words were to be maintained during articulatory suppression. During retention participants carried out a series of choice reaction tasks, which were used to measure central attentional demands of the maintenance strategies. Articulatory rehearsal had costs on processing RTs that lasted for 10 s. Maintenance of words during articulatory suppression did not yield persistent costs on central attention, implying that participants did not continuously refresh the words. Finally, the current results cast doubt on the idea that elaboration requires central attention for an extended period of time. All experimental scripts and data sets reported here are available online ( https://osf.io/69p8j/ ).

Previous research has claimed that working memory (WM) updating is one of three primary central executive processes, and the only one to reliably predict fluid intelligence. However, standard WM updating tasks confound updating requirements with generic WM functions. This article introduces a method for isolating a process unique to WM updating, namely the removal of no-longer relevant information. In a modified version of an established updating paradigm, to-be-updated items were cued before the new memoranda were presented. Overall, longer cue-target intervals—that is, longer time available for removal of outdated information—led to faster updating, suggesting that people can actively remove information from WM. Experiments 1 and 2 demonstrated that well-established effects of item repetition and similarity on updating RTs were diminished with longer cue-target interval, arguably because representational overlap between outdated and new information becomes less influential when outdated information can be removed prior to new encoding. Experiment 3 looked at individual differences, using the reduction of updating RTs to measure removal speed. Removal speed was measured reliably but was uncorrelated to WM capacity. We conclude that (1) removal of outdated information can be experimentally isolated and measured reliably, (2) removal speed is a unique, active WM updating ability, and (3) the view of WM updating as a core executive process that uniquely predicts fluid abilities is overstated.

The ability to keep working memory content up to date is vital for a number of higher cognitive functions such as navigation and reasoning, but it is also crucial for the effective operation of working memory itself. Removing outdated or irrelevant information allows focused processing of relevant information, and minimizes interference. We present evidence from three experiments that (1) people utilize an active removal process to update working memory, (2) that this removal process is an item-specific operation, and (3) that updating subsets of information held in working memory involves switching between maintenance and updating modes of working memory.

Theories assuming that representations in working memory decay unless maintained by rehearsal must predict that in any condition where rehearsal does not fully counteract decay, memory declines with a longer retention interval. Two experiments served to test this prediction in a complex-span paradigm in which encoding of letters for later recall alternated with series of spatial distractor operations. The opportunity for rehearsal was varied through cognitive load, the proportion of available time per distractor operation that was actually needed for that operation. The time needed for each operation within a series was measured independently. Retention interval was varied by increasing the number of operations at constant cognitive load. Memory declined with higher cognitive load, but was unchanged (Experiment 1) or improved (Experiment 2) with more distractor operations. Decay theories can explain the effect of cognitive load by assuming that at high load rehearsal fails to fully compensate decay, but then must predict a negative effect of the number of operations at higher cognitive load, contrary to the data. Simulations with an interference-based computational model of working memory, SOB-CS, show that the model explains the experimental findings.

The impact of working memory training on a broad set of transfer tasks was examined. Each of three groups of participants trained one specific functional category of working memory capacity: storage and processing, relational integration, and supervision. A battery comprising tests to measure working memory, task shifting, inhibition, and reasoning was administered before, immediately after, and 6 months after 4 weeks of computer-based training. Training groups were compared to an active control group practicing perceptual matching tasks. Data were analyzed with linear mixed-effects models that revealed distinct transfer profiles for the experimental groups: Storage-Processing training had an effect on working memory and reasoning, and Supervision training improved task shifting and reasoning. There was no such broad transfer of Relational Integration training. The degree of improvement in the training tasks correlated positively with the magnitude of transfer. Differential effects of training different functional categories of working memory and executive functions could explain why previous studies yielded mixed results: Training specific processes leads to transfer on specific cognitive constructs only.

This article presents four experiments that tested predictions of SOB (Serial Order in a Box), an interference-based theory of short-term memory. Central to SOB is the concept of novelty-sensitive encoding, which holds that items are encoded to the extent that they differ from already-encoded information. On the additional assumption that distractors are encoded into memory in the same manner as list items, the theory predicts differential effects of interfering activity based on the similarity structure of distractors. Consistent with predictions, three experiments showed that overt articulation of distractors in between recalls of list items did not affect forgetting when the same distractor was repeated multiple times, whereas forgetting was observed if several different distractors were articulated within the same time span. A fourth experiment showed that the absence of forgetting with repeated articulations of the same item was not due to compensatory attentional refreshing of memory traces. The data support the notion that forgetting from short-term memory arises from interference and are difficult to reconcile with temporal decay.

Reports two experiments on mechanism of interference in working memory. Experiment 1 shows that a target word in a memory list, which bears high similarity to one of 4 words read aloud in the retention interval, is recalled less well than a control word. A second target word, not similar to any word read aloud but with all its phonemes repeated among the words read aloud, suffered the same degree of impairment. Feature overwriting explains both results, whereas similarity-based confusion explains only the first. In Experiment 2, participants remembered lists of 4 words, followed by 4 letters. A target word with high phoneme overlap with the letters was recalled worse than a control word, in line with predictions from feature overwriting. A further target word with many phonological neighbors created by inserting letter phonemes into it was recalled better than a control, contrary to predictions from feature migration.

A mathematical model of working-memory capacity limits is proposed on the key assumption of mutual interference between items in working memory. Interference is assumed to arise from overwriting of features shared by these items. The model was fit to time-accuracy data of memory-updating tasks from four experiments using nonlinear mixed effect (NLME) models as a framework. The model gave a good account of the data from a numerical and a spatial task version. The performance pattern in a combination of numerical and spatial updating could be explained by variations in the interference parameter: assuming less feature overlap between contents from different domains than between contents from the same domain, the model can account for double dissociations of content domains in dual-task experiments. Experiment 3 extended this idea to similarity within the verbal domain. The decline of memory accuracy with increasing memory load was steeper with phonologically similar than with dissimilar material, although processing speed was faster for the similar material. The model captured the similarity effects with a higher estimated interference parameter for the similar than for the dissimilar condition. The results are difficult to explain with alternative models, in particular models incorporating time-based decay and models assuming limited resource pools.