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Two experiments with a working-memory updating task investigated dual-task interference between short-term storage of numerical and spatial material, between execution of a numerical and a spatial updating operation, and between storage and processing. Participants memorised a set of digits and a set of spatial positions, updated elements of both sets by a sequence of operations, and then recalled the final values. In Experiment 1, a single element in each memory set had to be updated several times. There was little interference between storage of the two sets, and between storage and processing, but parallel execution of the two operations was not possible. In Experiment 2, all elements in both memory sets were updated in random order. There was substantial interference between memory for the numerical and the spatial sets, and between storage and processing. Parallel execution of two operations was again not possible. Moreover, trying to do two operations simultaneously resulted in impaired memory of final results. The results support the distinction between the activated part of long-term memory that can hold elements currently not needed for processing, and a more central, capacity-limited part of working memory that provides access to its contents for processing
This study investigated whether older adults could acquire the ability to perform 2 cognitive operations in parallel in a paradigm in which young adults had been shown to be able to do so (K. Oberauer & R. Kliegl, 2004). Twelve young and 12 older adults practiced a numerical and a visuospatial continuous memory updating task in single-task and dual-task conditions for 16 to 24 sessions. After practice, 9 young adults were able to process the 2 tasks without dual- task costs, but none of the older adults had reached the criterion of parallel processing. The results suggest a qualitative difference between young and older adults in how they approach dual-task situations.
Parameters of a formal working-memory model were estimated for verbal and spatial memory updating of children. The model proposes interference though feature overwriting and through confusion of whole elements as the primary cause of working-memory capacity limits. We tested 2 age groups each containing 1 group of normal intelligence and 1 deficit group. For young children the deficit was developmental dyslexia; for older children it was a general learning difficulty. The interference model predicts less interference through overwriting but more through confusion of whole elements for the dyslexic children than for their age-matched controls. Older children exhibited less interference through confusion of whole elements and a higher processing rate than young children, but general learning difficulty was associated with slower processing than in the age-matched control group. Furthermore, the difference between verbal and spatial updating mapped onto several meaningful dissociations of model parameters.
We tested the limits of working-memory capacity (WMC) of young adults, old adults, and children with a memory-updating task. The task consisted of mentally shifting spatial positions within a grid according to arrows, their color signaling either only go (control) or go/no-go conditions. The interference model (IM) of Oberauer and Kliegl (2006) was simultaneously fitted to the data of all groups. In addition to the 3 main model parameters (feature overlap, noise, and processing rate), we estimated the time for switching between go and no-go steps as a new model parameter. In this study, we examined the IM parameters across the life span. The IM parameter estimates show that (a) conditions were not different in interference by feature overlap and interference by confusion; (b) switching costs time; (c) young adults and children were less susceptible than old adults to interference due to feature overlap; (d) noise was highest for children, followed by old and young adults; (e) old adults differed from children and young adults in lower processing rate; and (f) children and old adults had a larger switch cost between go steps and no-go steps. Thus, the results of this study indicated that across age, the IM parameters contribute distinctively for explaining the limits of WMC.
We tested the independent influences of two content-based factors on dual-task costs, and on the parallel processing ability: The pairing of S-R modalities and the pairing of relevant features between stimuli and responses of two tasks. The two pairing factors were realized across four dual-task groups. Within each group the two tasks comprised two different stimulus modalities (visual and auditory), two different relevant stimulus features (spatial and verbal) and two response modalities (manual and vocal). Pairings of S-R modalities (standard: visual-manual and auditory-vocal, non-standard: visual-vocal and auditory manual) and feature pairings (standard: spatial-manual and verbal-vocal, non-standard: spatial-vocal and verbal-manual) varied across groups. All participants practiced their respective dual-task combination in a paradigm with simultaneous stimulus onset before being transferred to a psychological refractory period paradigm varying stimulus-onset asynchrony. A comparison at the end of practice revealed similar dual-task costs and similar pairing effects in both paradigms. Dual-task costs depended on modality and feature pairings. Groups training with non-standard feature pairings (i.e., verbal stimulus features mapped to spatially separated response keys, or spatial stimulus features mapped to verbal responses) and non-standard modality pairings (i.e., auditory stimulus mapped to manual response, or visual stimulus mapped to vocal responses) had higher dual-task costs than respective standard pairings. In contrast, irrespective of modality pairing dual-task costs virtually disappeared with standard feature pairings after practice in both paradigms. The results can be explained by crosstalk between feature-binding processes for the two tasks. Crosstalk was present for non-standard but absent for standard feature pairings. Therefore, standard feature pairings enabled parallel processing at the end of practice. (C) 2016 Elsevier B.V. All rights reserved.