this article are also gratefully acknowledged

WhH subjectsswitch between two tasks, performance is slower after a taskswitch tht after a task repetition. We report five experimentsshperi thp a large part ofth)I "task-sh5S) costs" cannot be attributed to a control operation, needed to configureth cognitive system for th upcoming task (e.g., Rogers & Monsell, 1995). In all experiments subjects switchs between picture-naming and word-reading. We presented di#erent stimulieithl in just one of th two tasks, or inboth ofth9S ShSI#qH(93 were larger for stimuli presented inboth tasks ths forthH3 presented in only one task, even after more the 100 intervening trials between prime and probe events. We suggest (as proposed by Allport & Wylie, 2000)th0 stimuli acquire associationswith th tasks inwh9E th9 occur.Whu th current task activation is weak, as on aswitch of tasks, stimuli can trigger retrieval of th associated, competing task, provoking larger time costs.

The current state of A.D. Baddeley and G.J. Hitch’s (1974) multicomponent working memory model is reviewed. The phonological and visuospatial subsystems have been extensively investigated, leading both to challenges over interpretation of individual phenomena and to more detailed attempts to model the processes underlying the subsystems. Analysis of the controlling central executive has proved more challenging, leading to a proposed clarification in which the executive is assumed to be a limited The term working memory appears to have been first proposed by Miller, Galanter, and Pribram (1960) in their classic book Plans and the Structure of Behavior. The term has subsequently been used in computational modeling approaches (Newell & Simon, 1972) and in animal learning studies, in which the participant animals are required to hold information across a number of trials within the same day (Olton, 1979). Finally, within cognitive psychology, the term has been adopted to cover the system or systems involved in the temporary maintenance and manipulation of information. Atkinson and Shiffrin (1968) applied the term to a unitary short-term store, in contrast to the proposal of Baddeley and Hitch (1974), who used it to refer to a system comprising multiple components. They emphasized the functional importance of this system, as opposed to its simple storage capacity. It is this latter concept of a multicomponent working memory that forms the focus of the discussion that follows. I myself have been using the concept for over 25 years; does it still work? Before addressing this issue, it is perhaps appropriate to consider what are the criteria for working. The multicomponent model of working memory was proposed as a theoretical framework whose function was to give

Correct performance often depends on remembering the task one has been instructed to do. When the task periodically changes, memory for the current task must decay (lose activation) to prevent it from interfering with memory for the next task when that is encoded. Three task-switching experiments examine this decay process. Each shows within-run slowing, a performance decline occurring as memory for the current task decays. In experiment 1, slowing is attenuated when memory for the task is optional, suggesting that memory is indeed causal. Experiment 2 finds slowing despite a flat hazard rate for task instructions, suggesting that slowing is not an artifact of instruction anticipation. Experiment 3 finds slowing in the familiar alternatingruns paradigm (Rogers & Monsell, 1995), suggesting that it may lurk elsewhere. A process model of activation explains within-run slowing and relates it to switch cost and "restart cost" (Allport & Wylie, 2000) in functional terms.

Human perceptual and cognitive abilities are limited resources. Attention is the mechanism used to allocate such resources in the most effective way. Current technologies, in addition to allowing fast access to information and people, should be designed to support human attentional processes on which they impose further strain. This paper analyses the issues related to the design of systems capable of such support: Attention Aware Systems. We introduce the research aimed at understanding and modelling human attentional processes, including perceptual and cognitive processes as studied in cognitive psychology, as well as rhetorical, aesthetic, and social aspects related to attentional mechanisms. We analyse current approaches to the design of Attention Aware Systems along three major features: detection of user's current attentional state, detection and evaluation of possible alternative attentional states, strategies for focus switch or maintenance. Finally, we discuss the most promising research direction for the development of systems capable of supporting human attentional mechanisms.

this article. We also thank Phil Allen, Jim Johnston, Joel Lachter, and Roger Remington for their insight and valuable discussions

This study examined the performance of 41 patients with focal prefrontal cortical lesions and 38 healthy controls on a task-switching procedure. Three different conditions were evaluated: single tasks without switches and two switching tasks with the currently relevant task signalled either 1500 ms (Long Cue) or 200 ms (Short Cue) before the stimulus. Patients with Superior Medial lesions showed both a general slowing of reaction time (RT) and a significantly increased switch cost as measured by RT. No other prefrontal group showed this increased reaction time switch cost. Increased error rates in the switching conditions, on the other hand, were observed in patients with Inferior Medial lesions and, to a lesser extent, ones with Superior Medial lesions. Patients with left dorsolateral lesions (9/46v) showed slower learning of the task as indicated by a high error rate early on. Several different processes are involved in task-switching and these are selectively disrupted by lesions to specific areas of the frontal lobes.

this article without authors' permission) The Absence of A Switch Cost When Preparing for Multiple Tasks: Interactions Between Element- and Ensemble-Level Effects Mei-Ching Lien & Eric Ruthruff NASA Ames Research Center Six experiments examined an intriguing result from a dual-task study by De Jong (1995) where no task-switch cost was found. We investigated whether this phenomenon is due to the formation of task ensembles - a control structure covering more than one task element (e.g., prepare Task 1 and the switch to Task 2). Experiment 1, where tasks were performed individually, showed the usual large switch cost (182 ms). This cost disappeared and even reversed in Experiments 2-5, where the temporal and/or spatial contiguity between adjacent task elements was increased to encourage ensemble formation. In Experiment 6, the switch cost between elements was large within an ensemble, but small or nonexistent between ensembles. These data suggest that the element-level effect is fragile and can be reduced or eliminated when a higher-level control structure is formed. A dual-route model of task switching is proposed

this article should be addressed to MeiChing Lien, Mail Stop 262-4, NASA Ames Research Center, Moffett Field, California 94035. E-mail: mclien@mail.arc.nasa.gov Journal of Experimental Psychology: In the public domain Human Perception and Performance 2003, Vol. 29, No. 3, 692--712 DOI: 10.1037/0096-1523.29.3.692 692 trial a pair of stimuli was presented in one quadrant of a square, with one of the two stimuli being irrelevant. The irrelevant stimulus in the pair could indicate the same response as the relevant stimulus (congruent), the opposite response (incongruent), or it could be a neutral character. Across successive trials, the quadrant in which the pair appeared rotated in a clockwise manner, with the two top positions indicating one task and the two bottom positions indicating the other task to be performed. As a result, the repeat trials and switch trials were intermixed within a block, with the task sequence (e.g., AABB) known in advance

scaffolding