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Future research on cognitive control must precisely characterize the supervisory functions of executive mental processes. The achievement of this objective will be facilitated by formal concepts and algorithms from contemporary computer operating systems. In particular, operating-system fundamentals can help to advance work with the Executive-Process Interactive Control (EPIC) architecture, a theoretical framework for computational modeling of human multiple-task performance. EPIC models that incorporate general executive processes like those of operating systems provide insights about how people schedule tasks, allocate perceptual-motor resources, and coordinate task processes during multiple-task performance under both laboratory and real-world conditions. Such insights may lead to discoveries about the acquisition of procedural task knowledge and efficient multitasking skills.

According to a recent theory, anterior cingulate cortex is sensitive to response conflict, the coactivation of mutually incompatible responses. The present research develops this theory to provide a new account of the error-related negativity (ERN), a scalp potential observed following errors. Connectionist simulations of response conflict in an attentional task demonstrated that the ERN—its timing and sensitivity to task parameters—can be explained in terms of the conflict theory. A new experiment confirmed predictions of this theory regarding the ERN and a second scalp potential, the N2, that is proposed to reflect conflict monitoring on correct response trials. Further analysis of the simulation data indicated that errors can be detected reliably on the basis of post-error conflict. It is concluded that the ERN can be explained in terms of response conflict and that monitoring for conflict may provide a simple mechanism for detecting errors. Errors are an important source of information in the regulation of cognitive processes. The mechanism by which people detect and correct their errors has been the object of study for many years, but research interest has increased in recent years following the discovery of neural correlates of performance monitoring. In particular,

When subjects switch between a pair of stimulus–response tasks, reaction time is slower on trial N if a different task was performed on trial N � 1. We present a parallel distributed processing (PDP) model that simulates this effect when subjects switch between word reading and color naming in response to Stroop stimuli. Reaction time on ‘‘switch trials’ ’ can be slowed by an extended response selection process which results from (a) persisting, inappropriate states of activation and inhibition of task-controlling representations; and (b) associative learning, which allows stimuli to evoke tasks sets with which they have recently been associated (as proposed by Allport & Wylie, 2000). The model provides a good fit to a large body of empirical data, including findings which have been seen as problematic for this explanation of switch costs, and shows similar behavior when the parameters are set to random values, supporting Allport and Wylie’s proposal. © 2001 Elsevier Science Key Words: task switching; task set; Stroop effect; parallel distributed processing; executive functions. Atkinson and Shiffrin (1968) proposed a distinction between relatively permanent cognitive structures, such as short- and long-term memory, and control processes which harness those fixed structures in order to attain specific goals. This distinction was elaborated in the following years (e.g.,

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.

Considerable evidence indicates that a processing bottleneck constrains performance for temporally overlapping tasks by limiting response selection to one response at a time. However, Schumacher et al. (2001) report that dual-task costs are minimal when participants are given practice and instructed to place equal emphasis on the two tasks. We focus on whether such findings are compatible with the operation of an efficient bottleneck. In Experiment 1, participants trained until able to perform both tasks simultaneously without interference. Novel stimulus pairs produced similar reaction times to practiced pairs, demonstrating that the ability did not result from the development of compound stimulus-response associations. Manipulating the relative onset (Exps. 2 and 4) and duration (Exps. 3 and 4) of response selection processes did not lead to dual-task costs. Thus, the results indicate that the two tasks did not share a bottleneck after practice. 2 Performing two tasks at the same time can be extremely difficult. Psychologists have often visited this phenomenon to gain insight into the limits of human cognition. Why should the brain, considered the paragon of distributed computation, be so resistant to processing multiple, independent tasks in a parallel fashion? While the dominant finding is that simultaneous execution leads to dramatic decrements in the performance of one or both tasks (see Pashler, 1998), some important exceptions to this principle have been described (e.g. Spelke, Hirst and Neisser, 1976). However, in many of these exceptional cases, the level of analysis is not sufficiently sensitive to provide answers about how proficient dual-task performance is achieved. That is, the timing of the two tasks is not adequately controlled to determine whether crit...

Participants switched between two randomly ordered, two-choice reaction-time (RT) tasks, where an instructional cue preceded the target stimulus and indicated which task to execute. Task-switching cost dissipated passively while the participants waited for the instructional cue in order to know which task to execute (during the Response–Cue Interval). Switching cost was sharply reduced, but not abolished, when the participants actively prepared for the task switch in response to the instructional cue (during the Cue–Target Interval). The preparation for a task switch has shown not to be a by-product of general preparation by phasic alertness or predicting target onset. It is suggested that task-switching cost has at least three components reflecting (1) the passive dissipation of the previous task set, (2) the preparation of the new task set, and (3) a residual component. © 2000 Academic Press Compared to the wealth of empirical evidence regarding elementary cognitive process, relatively little is known on how these processes are controlled (Logan, 1985; Monsell, 1996). One paradigm to study cognitive control is task switching, in which participants rapidly switch between two or more choice reaction-time (RT) tasks. In most circumstances, switching tasks is associated with a sizable decrement in performance (called switching cost)

... In this article I define a taxonomy and three dimensions of simulated task environments. The dimensions are based on viewing simulated task environments from the perspectives of the researcher, the task, and the participants. Research on complex systems is inherently complex. It is my hope that the terms and distinctions introduced in this article will further the scientific enterprise by enabling us to spend less time explaining our paradigms and more time communicating our results

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.

Unexpected interruptions introduced during the execution phase of simple Tower of London problems incurred a time cost when the interrupted goal was retrieved, and this cost was exacerbated the longer the goal was suspended. Furthermore, time taken to retrieve goals was greater following a more complex interruption, indicating that processing limitations may be as important as time-based limitations in determining the ease of goal retrieval. Such findings cannot simply be attributed to task-switching costs and are evaluated in relation to current models of goal memory (E. M. Altmann & G. J. Trafton, 2002; J. R. Anderson & S. Douglass, 2001), which provide a useful basis for the investigation and interpretation of interruption effects.