The Research Of Cue Mechanism In Task Rule Shifting

Task cue-target alternating paradigm was the classical paradigm to study task rule shifting, the typical task cue switching paradigm included two kinds of different tasks, according to the cue to process and implement, which attracted the attention of many researchers was focus on the task cue. This research on the basis of task rule shifting to investigate the characteristics of task cues. Three experiments were designed in this study, and the basic rule was parity task or magnitude task, it is that, according the cue to judge the number was odd-even or less than 5- more than 5(1-9,except 5). The first experiment was on the basis of domestic and foreign literature and introducing the concept of probability to design. The experiment set three different situations: infrequency(25%), intermediate frequency(50%), frequency(75%). Studying the influence of three different cue repeating frequencies to task rule shifting; The second experiment was on the basis of the first one, and introducing the concepts of task selection and task execution, which the task selection had two cases, one was that the task selection was consistent with the task implementation, and the other was the task selection was inconsistent with the task implementation, designing two different cases to study the influence of task se lection to task execution in task rule shifting; The third experiment was on the basis of the literature and the development of experimental apparatus ERP, introducing the concepts of high hierarchal level rule and low hierarchal level rule, designing nove l experiment procedure, in which the low hierarchal level rule was hidden in the high hierarchal level rule, to study the influence of different hierarchal level rules on the rule shifting according to ERP. The results showed as follows:(1) The first one found that, the reaction time of parity task was longer than the magnitude task, and the result may associated with digital space processing; the cue repetition frequency was higher, the task rule shifting switching cost was larger.(2) Consistent with the first one, the second experiment also found that, during the process of the task execution, the reaction time of parity task was longer than the magnitude task, and the cue repetition frequency was higher, the task rule shifting switching cost was larger. Two new findings was in the second experiment, one was that, to task selection, the subject had preferences, compared with the reaction time of parity task and the frequency of parity task, the reaction time of magnitude task was longer and the frequenc y of magnitude task was higher; the other one was that the effect of task selection on the task execution was endogenous effect, was bottom- up controlled. Compared with the case of task selection was consistent the task execution, the rule shifting switching cost of the case of task selection was inconsistent the task execution was larger.(3) The ERP results in the third experiment showed that: The P2 and late positive component(LPC) were enhanced in high shifting trials when compared with low shifting trials for the cue stimuli; An increased LPC was evoked by the high hierarchical level of rule shifting when compared with low shifting for the target stimuli. These findings extend previous studies on task switching by providing evidence that the rule shifting is conducted hierarchically during the early time window after cue presentation. The behavior dates showed that the high hierarchal level rule shifting switching cost was larger than the low hierarchal level rule shifting switching cost.