The task-switching paradigm is being increasingly used as a tool for studying cognitive control and task coordination. Different procedural variations have been developed. They have in common that a comparison is made between transitions in which the previous task is repeated and transitions that involve a change toward another task. In general, a performance switch cost is observed such that switching to a new task results in a slower and more error-prone execution of the task. The present article reviews the theoretical explanations of the switch cost and the findings collected in support of those explanations. Resolution and protection from interference by previous events explain part of the switching cost, but processes related to task setting and task preparation also play a prominent role, as testified by faster execution and lower switch costs when the preparation time is longer. The authors discuss the evidence in favor of each of these sets of accounts and raise a number of questions that situate task switching in a broader context of cognitive control processes. The role of several aspects of the task set, including task variations, task-set overlap, and task-set structure, is addressed, as is the role of knowledge about probability of task changes and about the structure of task sequences.

In cognitive research, speed and accuracy are two important aspects of performance. When analyzed separately, these performance variables sometimes lead to contradictory conclusions about the effect of a manipulation. To avoid such conflicts, several measures that integrate speed and accuracy have been proposed, but the added value of using such measures remains unclear. The present paper compares the relative utility of seven integrated performance measures, namely four variations on a binning procedure that weights response times of correct and incorrect trials differently, and three measures that combine averaged speed and accuracy scores. The properties of these integrated measures were explored in three simulation studies. The first study compared three binning measures and showed that one measure failed to grasp the performance difference between two conditions. The second study showed that the sampling distributions of the measures were symmetric, except for a strong skewness on the rate correct score. The third study varied the trade-off and the effect sizes of speed and accuracy in four different combinations of size and direction of speed and accuracy effects. These studies highlighted some further shortcomings of the binning measures. The combination measures performed well, but linear integration of speed and accuracy and rate correct score were most efficient in detecting effects and accounting for a larger proportion of the variance. The paper concludes that these combination measures are useful provided that the speed and accuracy data are also inspected.

A computerized version of the Corsi blocks task (Milner, 1971) was assessed for standard forward-recall order (Experiments 1 and 3) and for reversed-recall order (Experiments 2 and 3) either in a single-task or in a dual-task design combined with articulatory suppression, matrix-tapping, random-interval generation or fixed-interval generation as concurrent tasks during the encoding stage. Concurrent performance of the matrix-tapping task impaired memory performance for short as well as for longer block sequences. The random-interval generation task, which loads executive processes, impaired memory performance mainly at intermediate- and longer-sequence lengths, while fixed-interval generation, which is presumed to put no load on executive processing, did not show any effect. Articulatory suppression did not impair memory performance on forward-recall order, but it impaired memory for longer sequences in the backward-recall condition in Experimentt 2, but not in Experiment 3. The results are discussed within the context of the working-memory model of Baddeley and Hitch (1974

The current study tested the development of working memory involvement in children's arithmetic strategy selection and strategy eYciency. To this end, an experiment in which the dual-task method and the choice/no-choice method were combined was administered to 10-to 12-year-olds. Working memory was needed in retrieval, transformation, and counting strategies, but the ratio between available working memory resources and arithmetic task demands changed across development. More frequent retrieval use, more eYcient memory retrieval, and more eYcient counting processes reduced the working memory requirements. Strategy eYciency and strategy selection were also modiWed by individual diVerences such as processing speed, arithmetic skill, gender, and math anxiety. Short-term memory capacity, in contrast, was not related to children's strategy selection or strategy eYciency.

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