Participants performed choice reaction time (RT) tasks on 2-dimensional stimuli such that each task was based on 1 stimulus dimension. A cue preceded the target stimulus and instructed the participant about which (randomly selected) task to perform. Shifting between tasks was associated with an RT cost, which was larger when the (randomly varying) cue-target interval was short as opposed to when it was long. Cue-target interval was not confounded with the remoteness from the previous trial. Hence, it affected the task-shift cost through preparation rather than by allowing carryover effects to dissipate. Similar results were obtained for 2 location tasks and for the object-based tasks (color and shape discrimination). They indicate a time-effort consuming process that operates after a task shift, precedes task execution, and presumably reflects the advance reconfiguration of processing mode. Cognitive psychologists have developed complex models to describe how participants perform on individual tasks. However, much less attention has been devoted to understanding the processes by which participants shift between tasks. There are at least three reasons why task shifting is important. First, patients with lesions in the frontal cortex show impairment in their ability to shift between tasks (Shallice & Burgess, 1991) and in the ability to switch attention between perceptual dimensions (

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) 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)

This article describes a quantitative model, which suggests what the underlying mechanisms of cognitive control in a particular task-switching paradigm are, with relevance to task-switching performance in general. It is suggested that participants dynamically control response accuracy by selective attention, in the particular paradigm being used, by controlling stimulus representation. They are less efficient in dynamically controlling response representation. The model fits reasonably well the pattern of reaction time results concerning task switching, congruency, cue-target interval and response-repetition in a mixed task condition, as well as the differences between mixed task and pure task conditions.

Poorer performance in conditions involving task repetition within blocks of mixed tasks relative to task repetition within blocks of single task is called mixing cost (MC). In 2 experiments exploring 2 hypotheses regarding the origins of MC, participants either switched between cued shape and color tasks, or they performed them as single tasks. Experiment 1 supported the hypothesis that mixed-tasks trials require the resolution of task ambiguity by showing that MC existed only with ambiguous stimuli that afforded both tasks and not with unambiguous stimuli affording only 1 task. Experiment 2 failed to support the hypothesis that holding multiple task sets in working memory (WM) generates MC by showing that systematic manipulation of the number of stimulus-response rules in WM did not affect MC. The results emphasize the role of competition management between task sets during task control.Keywords: task switching, switching cost, mixing cost, task ambiguity, working memory One of the prominent questions in psychological research concerns behavior control. Whereas the behaviorists' tradition has ascribed most behavioral control to the environment, recent cognitive theorists have emphasized more internally driven, top-down forms of control. This idea of cognitive control involves concepts such as goal-directed behavior, initiation, executive control processes, and so forth. A key concept in the context of top-down control is the task-set. According to Rogers and Monsell (1995), the control of task-sets is manifested in the ability to configure processing resources to perform one rather than another of the many cognitive tasks that a stimulus affords.A common paradigm for studying task-set control is the taskswitching paradigm. In the original version of this paradigm, performance in blocks of trials in which a task is repeated is compared with performance in blocks in which the participants switch between two different tasks (Allport, Styles, & Hsieh, 1994;Jersild, 1927;Spector & Biederman, 1976). More recent studies have used a modified paradigm that makes it possible to contrast task-switch trials and task-repetition trials within blocks of mixed tasks (e.g., De Jong, 1995bGoschke, 2000;Mayr & Keele, 2000;Meiran, 1996;Rogers & Monsell, 1995). In most cases, switching tasks is accompanied by a robust performance cost, seen both in reaction time (RT) and error rates, indicating switch cost.A recent conceptualization that incorporates knowledge from the variety of task-switching paradigms elaborates and sharpens the understanding of the switch mechanisms by differentiating between several cost components. The difference in performance between switch and repetition trials (in mixed-tasks blocks) is termed switching cost, and the difference between repetition trials (in mixed-tasks blocks) and single-task trials (in pure blocks) is termed mixing cost (

Real-life emotion regulation often occurs at some point after an emotion-triggering event (ETE) has been introduced, but most previous research has involved regulation before or after the ETE. In a series of experiments, the authors examined online regulation via distraction and cognitive reappraisal by manipulating the strategy initiation point in sadness-evoking films. Distraction was effective even when initiated late, presumably because it involves diluting the ETE contents by mixing them with a nonsad input. By contrast, reappraisal was less effective when initiated late, suggesting a possible point of no return for this strategy: Adopting a detached view late in the ETE may be difficult because it involves continued focus on the ETE and hence requires overcoming a previously formed tendency of identifying with the emotional content.