Visual, auditory, and cross-modality dual-task costs: electrophysiological evidence for an amodal bottleneck on working memory consolidation

When two masked, attended targets (T1 and T2) are presented within approximately half a second of each other, report of T2 is poor, compared with when the targets are presented farther apart in time--a phenomenon known as the attentional blink (AB; Raymond, Shapiro, & Arnell, 1992). Some researchers have suggested that an amodal bottleneck on working memory consolidation underlies the AB (see, e.g., Arnell & Jolicoeur, 1999). In the present work, T1 was masked, whereas T2 was unmasked. The modality of T1 (visual or auditory) and the modality of T2 (visual or auditory) were factorially manipulated across four experiments. For all modality combinations, T2's P3 event-related brain potential component was found to be delayed when T2 was presented soon after T1 (lag 3), compared with when T1 and T2 were presented farther apart (lag 8). Results suggest that the working memory consolidation bottleneck is amodal in nature, and provide evidence that visual, auditory, and cross-modality ABs all result from a bottleneck on consolidation operations.     

Raven's matrices and working memory: A dual-task approach

The cognitive system does not just act as a mirror from the sensory input; instead, it tends to normalize this information. Given that letter processing seems to be much more specialized than digit processing in the cortex, we examined whether the regularization process occurs differently from digits to letters than from letters to digits: We employed a masked priming same/different experiment (e.g., probe, VESZED; prime, V35Z3D ; and target, VESZED). When embedded in letter strings, digits that resemble letters (e.g., 3 and 5 in V35Z3D -VESZED) tend to be encoded in a letter-like manner, whereas when embedded in digit strings, letters that resemble digits (e.g., E and S in 9ES7E2–935732) tend not to be encoded in a digit-like manner.     

Simultaneous cognitive operations in working memory after dual-task practice

The authors tested the hypothesis that with adequate practice, people can execute 2 cognitive operations in working memory simultaneously. In Experiment 1, 6 students practiced updating 2 items in working memory through 2 sequences of operations (1 numerical, 1 spatial). In different blocks, imperative stimuli for the 2 sequences of operations were presented either simultaneously or sequentially. Initially, most participants experienced substantial dual-task costs. After 24 sessions of practice, operation latencies for simultaneous presentation were equal to the maximum of times for the 2 operations in the sequential condition, suggesting perfect timesharing. Experiment 2 showed that a reduction of dual-task costs requires practice on the combination of the 2 updating tasks, not just practice on each individual task. Hence, the reduction of dual-task costs cannot be explained by shortening or automatization of individual operations.     

Evidence for disproportionate dual-task costs in older adults for episodic but not semantic memory

Previous research demonstrates that older adults are poor at dual tasking, but there is less agreement on whether their decrement is worse than that predicted from single-task performance. This study investigated whether task domain moderates dual-task costs in old age. In two experiments, young and older adults retrieved either previously learned associates (episodic retrieval) or overlearned category members (semantic retrieval) under single or working-memory load conditions, using cued recall (Experiment 1) and recognition (Experiment 2) procedures. In both experiments the proportional costs of dual tasking were age invariant for semantic retrieval but were particularly marked for episodic retrieval, although the size of the age effect was reduced in recognition compared to cued recall. The data suggest that age effects in dual tasking may be domain specific.     

Age-related differences in working memory and force control under dual-task conditions

The aim of this study was to investigate the relationship between force control and cognitive performance under dual-task conditions in younger (18-22 years) and older adults (65-77 years). Cognitive (n-back test) and motor performance (force-tracking) was measured independently and simultaneously. Results indicated overall age-related differences for the n-back and the force-tracking task. Age-related differences increased during dual-task conditions. While younger adults exhibited no decrease in cognitive or motor performance during dual-task conditions, older adults showed a decrease in motor and cognitive performance. Additionally, when older adults made an error in the cognitive task they tended to show greater variability in the force-tracking task. These results suggest that cognitive motor deficits are responsible for older adults' performance decrements under dual-task conditions.     

Field dependence-independence from a working memory perspective: a dual-task investigation of the Hidden Figures test

Field dependence-independence (FDI) is a construct intensively investigated within cognitive style research, but its cognitive underpinnings are not clearly specified. We propose that performance on FDI tasks primarily reflects the operations of the visuospatial and executive components of working memory. We tested this hypothesis in a dual-task experiment with a commonly used measure of FDI, the Hidden Figures Test. The results showed that performance on this test was impaired by concurrent performance of secondary tasks that primarily tap the visuospatial component (spatial tapping) and the executive component (2-back and random number generation), but was almost unaffected by other secondary tasks (simple tapping and articulatory suppression). Moreover, an analysis of secondary task performance ruled out the possibility of strategic trade-offs and revealed an intriguing dissociation for two different sets of "randomness" indices for the random number generation task. These results support the hypothesised mapping between FDI and working memory components and suggest that the dual-task paradigm can provide a useful way to bring underspecified constructs like FDI into closer alignment with theoretical ideas developed within cognitive psychology.     

Searching while loaded: Visual working memory does not interfere with hybrid search efficiency but hybrid search uses working memory capacity

In “hybrid search” tasks, such as finding items on a grocery list, one must search the scene for targets while also searching the list in memory. How is the representation of a visual item compared with the representations of items in the memory set? Predominant theories would propose a role for visual working memory (VWM) either as the site of the comparison or as a conduit between visual and memory systems. In seven experiments, we loaded VWM in different ways and found little or no effect on hybrid search performance. However, the presence of a hybrid search task did reduce the measured capacity of VWM by a constant amount regardless of the size of the memory or visual sets. These data are broadly consistent with an account in which VWM must dedicate a fixed amount of its capacity to passing visual representations to long-term memory for comparison to the items in the memory set. The data cast doubt on models in which the search template resides in VWM or where memory set item representations are moved from LTM through VWM to earlier areas for comparison to visual items.     

Searching short-term memory for linear-positioning movements

To determine whether memory search for movements was serial or parallel, the search processes involved in a short-term motor-memory paradigm were investigated. A linear-positioning task was used to present a series of 1, 2, or 3 movements in a memory set. Upon completion of a memory set, subjects were presented with a search movement. The search movement was either the same length as one of the memory-set movements ("yes" response) or a different length ("no" response). Four subjects completed three consecutive days of testing. On Day 1 RT and movement length were practiced. On Day 2 the subjects were required to search a memory set of movements and respond in the yes condition by lifting the index finger of the left hand. This movement terminated a RT search clock. The same procedures were followed on Day 3, except that a no response was indicated by lifting the index finger. A 2 X 3 X 3 (response X memory set X RT trials) within-subjects analysis yielded nonsignificant main effects and interactions. The results were discussed in relation to verbal memory.     

Age- and practice-related influences on dual-task costs and compensation mechanisms under optimal conditions of dual-task performance

Impaired dual-task performance in younger and older adults can be improved with practice. Optimal conditions even allow for a (near) elimination of this impairment in younger adults. However, practice effects under these conditions in older adults are unknown. Further, it is open, how changed task scheduling and/ or the acquisition of task coordination skills affect the temporal overlap of two tasks in different age groups; this overlap indicate the involvement of these practice-related mechanisms to compensate for impaired dual-task performance. In a dual-task situation of Schumacher et al. (2001 , Psychological Science, 12, 230) including optimal conditions for dual-task performance, both younger and older adults were able to achieve an improvement in dual-task performance with 8 practice sessions to the same degree. The temporal task overlap changed similarly in both age groups during these sessions demonstrating a similar degree of the involvement of compensation mechanisms in younger and older adults. At the end of practice, however, we showed that older adults do not achieve the same optimized dual-task performance level of younger adults.     

Parallel memory retrieval in dual-task situations: II. Episodic memory

Three experiments asked whether subjects could retrieve information from a 2nd stimulus while they retrieved information from a 1st stimulus. Subjects performed recognition judgments on each of 2 words that followed each other by 0, 250, and 1,000 ms (Experiment 1) or 0 and 300 ms (Experiments 2 and 3). In each experiment, reaction time to both stimuli was faster when the 2 stimuli were both targets (on the study list) or both lures (not on the study list) than when 1 was a target and the other was a lure. Each experiment found priming from the 2nd stimulus to the 1st when both stimuli were targets. Reaction time to the 1st stimulus was faster when the 2 targets came from the same memory structure at study (columns in Experiment 1; pairs in Experiment 2; sentences in Experiment 3) than when they came from different structures. This priming is inconsistent with discrete serial retrieval and consistent with parallel retrieval.     

Parallel memory retrieval in dual-task situations: I. Semantic memory

Can participants retrieve information about the 2nd of 2 stimuli while they are processing the 1st? Four experiments suggest they can. Reaction times to the 1st stimulus were faster if it came from the same category as the 2nd than if it came from a different category. This category-match effect was observed for letter-digit discrimination (Experiment 1), magnitude and parity judgments about digits (Experiment 2), and lexical decisions (Experiment 3). Experiment 4 showed that the 2nd stimulus could semantically prime the 1st. The category-match effect was observed only when the same task was performed on the 2 stimuli. When the task changed from the 1st stimulus to the 2nd, there was no advantage of a category match. This dependence on task set may explain previous failures to find parallel retrieval.     

Searching for serial refreshing in working memory: Using response times to track the content of the focus of attention over time

One popular idea is that, to support the maintenance of a set of elements over brief periods of time, the focus of attention rotates among the different elements, thereby serially refreshing the content of working memory (WM). In the research reported here, probe letters were presented between to-be-remembered letters, and response times to these probes were used to infer the status of the different items in WM. If the focus of attention cycles from one item to the next, its content should be different at different points in time, and this should be reflected in a change in the response time patterns over time. Across a set of four experiments, we demonstrated a striking pattern of invariance in the response time patterns over time, suggesting either that the content of the focus of attention did not change over time or that response times cannot be used to infer the content of the focus of attention. We discuss how this pattern constrains models of WM, attention, and human information processing.     

Working memory capacity and dual-task interference in picture naming

Researchers have found no agreement on whether dual-task interference in language performance, such as dual-task interference from tone discrimination on picture naming, reflects passive queuing or active scheduling of processes for each task. According to a passive-queuing account, while a central response-selection bottleneck is occupied by the tone discrimination task, picture naming is held in a passive queue until the bottleneck is freed. In contrast, according to an active-scheduling account, participants determine the order in which the tasks proceed, monitor progress on the tasks, suspend picture naming and hold it in working memory, and determine when to resume picture naming. Here, we report a study that assessed the relative merits of the queuing and scheduling accounts by examining whether the magnitude of dual-task interference in picture naming is associated with individual differences in the capacity of monitoring and updating of working memory representations, as assessed by the operation-span task. We observed that the updating/monitoring ability correlated with the speed of picture naming and with the magnitude of the interference from tone discrimination on picture naming. These results lend support to the active-scheduling account of dual-task interference in picture naming.     

Visual working memory for observed actions

Human society depends on the ability to remember the actions of other individuals, which is information that must be stored in a temporary buffer to guide behavior after actions have been observed. To date, however, the storage capacity, contents, and architecture of working memory for observed actions are unknown. In this article, the author shows that it is possible to retain information about only 2-3 actions in visual working memory at once. However, it is also possible to retain 9 properties distributed across 3 actions almost as well as 3 properties distributed across 3 actions, showing that working memory stores integrated action representations rather than individual properties. Finally, the author shows that working memory for observed actions is independent from working memory for object and spatial information. These results provide evidence for a previously undocumented system in working memory for storing information about actions. Further, this system operates by the same storage principles as visual working memory for object information. Thus, working memory consists of a series of distinct yet computationally similar mechanisms for retaining different types of visual information.     

Distraction biases working memory for faces

Psychonomic Bulletin & Review - Working memory persists in the face of distraction, yet not without consequence. Previous research has shown that memory for low-level visual features is...     

Implicit working memory

Working Memory (WM) plays a crucial role in many high-level cognitive processes (e.g., reasoning, decision making, goal pursuit and cognitive control). The prevalent view holds that active components of WM are predominantly intentional and conscious. This conception is oftentimes expressed explicitly, but it is best reflected in the nature of major WM tasks: All of them are blatantly explicit. We developed two new WM paradigms that allow for an examination of the role of conscious awareness in WM. Results from five studies show that WM can operate unintentionally and outside of conscious awareness, thus suggesting that the current view should be expanded to include implicit WM.     

What's working in working memory: a role for the Central Executive

Two experiments are reported which seek to explore the nature of the Central Executive of Baddeley's (Baddeley and Hitch, 1974) model of working memory. Experiment 1 uses a dual task methodology to compare performance on two storage tasks, making use of the two slave systems, the Phonological Loop (PL) and the Visuo-Spatial Scratch Pad (VSSP). Results suggest that storage can be thought of as based on the use of slave system independent resources. Experiment 2 uses a similar approach to compare performance on 2 processing tasks, again one PL based, the other VSSP based. These results suggest that processing is based on a central, shared set of resources. The two experiments support both a multiple resources model of working memory and more specifically identify a role for the Central Executive.     

Three layers of working memory: Focus-switch costs and retrieval dynamics as revealed by the N-count task

Two experiments explored the process of switching items in and out of the focus of attention using a new paradigm, the N-count task (adapted from Garavan, 1998; N varied from 1 to 4). This task yielded a focus size of one, indicated by a substantial focus-switch cost for 2-count. Additionally, the focus-switch costs in response time increased with working memory load, indicating an effortful search process occurring at a speed of about 240 ms/item. Maintaining and switching to and from a passive load did not increase the focus-switch costs or decrease memory accuracy, indicating that there is no crosstalk between passive and active items. The results support a concentric theory of working memory: a small focus at its core, a surrounding area of (at least) three readily available items referred to as the outer store, and a still wider region of passive storage, possibly more long-term memory than working memory.