预知任务转换的内源性准备和外源性调节

采用ERP探究在预知条件下任务转换的神经机制。使用“任务转换”实验范式,以汉字（名词/动词）或数字（奇数/偶数）的归类为任务。被试执行任务重复（AA,BB,…）或在两个任务间转换（AB,BA,…）,每个任务序列为连续的两个任务（任务1,任务2）。结果发现,任务1中,在刺激呈现后300ms左右,数、词的转换序列与重复序列出现显著差异;在中央区,320ms左右,任务1中转换序列比重复序列、任务2中转换任务比重复任务都产生一个更为负走向的波。这些结果表明,在预知条件下,简单任务转换的内源性准备可能开始于任务1呈现后300ms左右;内源性准备和外源性调节可能都反映了认知冲突过程,此认知冲突可能是转换代价的主要来源     

内源性注意与外源性注意对数字加工的不同影响

分别采用内源性注意和外源性注意实验范式,材料为小数（1－4）和大数（6－9）的中文与阿拉伯数字,任务为判断数字是否大于5,考察在注意与非注意条件下不同大小数字加工的距离效应和符号效应。结果发现：⑴在内源性线索和外源性线索的注意条件下,大小数都出现了距离效应;但在非注意条件下,内源性线索时的大小数都出现了距离效应,而外源性线索时只有小数出现了距离效应,大数的距离效应明显减弱或消失。⑵在内源性线索和外源性线索的注意条件下,大小数都没有出现符号效应;但在非注意条件下,大数没有出现符号效应,而小数出现了符号效应（阿拉伯数字的绩效比中文数字差）,并且内源性线索时的符号效应强度小于外源性线索。     

内源性注意和外源性注意对中小学生SNARC效应的影响

采用内源性注意和外源性注意实验范式,以判断数字奇偶为任务,材料为1～9的阿拉伯数字,考察内源性和外源性线索不同注意条件下中小学生的数字加工SNARC效应。结果发现:(1)内源性线索和外源性线索条件下,中小学生在数字加工任务中所表现出来的SNARC效应随着年龄增长逐渐增大;(2)内源性线索和外源性线索注意条件下,各年级学生均表现出显著的SNARC效应;(3)内源性线索非注意条件下,中学生能够表现出显著的SNARC效应,但小学生的SNARC效应不明显;外源性线索非注意条件下,高中生能够表现出显著的SNARC效应,但小学生和初中生的SNARC效应不明显,说明外源性注意对中小学生数字加工SNARC效应的影响比内源性注意大,且对SNARC效应的影响主要表现在较大的数字8和9上。     

任务转换和目标变化下的自我加工优势

通过联结学习任务和线索转换任务探讨自我关联刺激在任务转换和目标变化下的加工优势。结果发现：（1）相比于朋友和生人，自我更容易学习联结；（2）在线索转换任务中，所有关联刺激均未出现任务转换成本；（3）在目标变化条件下，自我关联刺激的目标结转效率最佳。结果表明自我关联刺激能够调节任务转换成本，并且在目标变化条件下能快速聚焦注意，表现出基于感知的特异性加工优势。     

不同趋近动机强度积极情绪对认知控制的影响

情绪的动机维度模型认为, 积极情绪对认知加工的影响受其趋近动机强度的调节, 高、低趋近动机积极情绪对认知加工的影响不同。本研究运用情绪图片诱发被试高、低趋近动机积极情绪, 采用停止信号任务和任务转换作业考察了不同趋近动机强度积极情绪对认知控制的影响。结果发现：(1)与中性条件相比, 高趋近动机积极情绪促进了停止信号任务中Go任务和任务转换作业中重复任务的反应执行。(2)在停止信号任务中, 相对于中性条件, 低趋近动机积极情绪条件下的停止信号反应时显著缩短; 在任务转换作业中, 低趋近动机积极情绪条件下的反应时转换损失和错误率转换损失均显著降低, 而高趋近动机积极情绪条件下的反应时转换损失显著增加。因此, 积极情绪对认知控制的影响受其趋近动机强度的调节, 即低趋近动机积极情绪增强认知灵活性, 提高停止反应与任务转换的速度; 而高趋近动机积极情绪增强认知稳定性, 加快停止信号任务中Go任务和任务转换作业中重复任务的反应执行, 增加了反应时转换损失。     

汉字加工中呈现速率对重复知盲效应的影响

实验采用RSVP任务,考察了汉字加工中呈现速率对重复知盲效应的影响,结果发现：（1）在加工汉字重复刺激时,存在着重复知肓（RB）效应,其强度随着呈现速率的变化而改变,当呈现速率较快时,正确率较低,呈现速率较慢时,正确率较高;（2）与加工英文信息比较,在汉字加工中,RB效应的出现似乎推迟了一段时间,这可能从另一方面反映出加工汉字比英文需要不同的加工时间．即加工信息的难易程度也影响RB效应出现的时间。     

视觉选择性注意对注意缺损多动障碍儿童数字距离效应的影响

采用Posner的内源性和外源性线索实验范式,材料为1~9的阿拉伯数字(不包括5),以判断目标数字是否大于5为任务,考察视觉选择性注意中的内源性注意和外源性注意对注意缺陷型多动障碍儿童(ADHD)数字加工距离效应的影响。结果发现:(1)内源性和外源性注意条件下,正常儿童在数字判断加工任务中的反应时短于ADHD儿童;(2)内源性有效线索提示条件下,ADHD儿童和正常儿童均表现出显著的数字距离效应;而无效线索提示条件下,ADHD儿童的大小数字距离效应均不明显,正常儿童仍然表现出显著的数字距离效应;(3)外源性有效线索提示条件下,ADHD儿童的小数字距离效应显著,但大数字距离效应不明显,正常儿童则表现出显著的大小数字距离效应;而无效线索提示条件下,只有正常儿童表现出显著的数字距离效应,ADHD儿童的数字距离效应不显著。     

准备时间和预先信息对任务切换的影响

两个实验采用任务线索范式,考察了准备时间和预先信息对任务切换的影响。实验1的准备时间为可预测,实验2的为不可预测,以考察准备时间的可预测性对任务切换的影响。以被试执行重复任务、切到任务和切离任务的正确反应时为主要指标,结果：（1）在准备时间可预测和不可预测两种条件下,准备时间和预先信息之间存在显著交互作用。在可预测条件中,重复和切到任务的反应时随着准备时间的增加而减少,但切到代价无显著变化,切离任务的反应时不受准备时间的影响,切离代价表现出反准备效应;不可预测条件下,三种任务的反应时都随着准备时间的增加而减少,但是切到和切离代价表现出反准备效应;（2）切离任务的反应时和代价显著高于切到任务的反应时和代价;（3）在这两种条件下,都没有出现切换代价的准备效应     

内外源性空间注意对多感觉整合的影响

本文采用内-外源性空间线索靶子范式, 操控内源性线索有效性(有效线索、无效线索)、外源性线索有效性(有效线索、无效线索)、目标刺激类型(视觉刺激、听觉刺激、视听觉刺激)三个自变量。通过两个不同任务难度的实验(实验1: 简单定位任务; 实验2: 复杂辨别任务)来考察内外源性空间注意对多感觉整合的影响。两个实验结果均发现外源性空间注意显著减弱了多感觉整合效应, 内源性空间注意没有显著增强多感觉整合效应; 实验2中还发现了内源性空间注意会对外源性空间注意减弱多感觉整合效应产生影响。结果表明, 与内源性空间注意不同, 外源性空间注意对多感觉整合的影响不易受任务难度的调控; 当任务较难时内源性空间注意会影响外源性空间注意减弱多感觉整合效应的过程。由此推测, 内外源性空间注意对多感觉整合的调节并非彼此独立、而是相互影响的。     

不同注意条件下的空间－数字反应编码联合效应

考察在无线索、内源性线索与外源性线索时不同符号数字在注意与非注意条件下的空间－数字的反应编码联合效应（Spatial Numerical Association of Response Codes,简称SNARC效应）。采用1到9的中文与阿拉伯数字为材料,以判断数字奇偶为任务。实验结果表明：⑴无线索时注意条件下阿拉伯和中文数字都出现了SNARC效应,而非注意条件下则都没有出现,并且受影响的主要是较大的数字（8、9）;⑵外源性线索和内源性线索时,我们得到一个逐渐递减的SNARC效应,受影响的也主要是较大的数字（8、9）。在内源性线索的注意条件阿拉伯和中文数都有SNARC效应,而在非注意条件只有阿拉伯数有SNARC效应;在外源性线索的注意条件只有阿拉伯数有SNARC效应,而在非注意条件阿拉伯和中文都没有SNARC效应,说明外源性注意的影响比内源性注意更大,中文数字所受的影响比阿拉伯数字更大。     

刺激类型与预先信息对任务切换的影响

为揭示联结竞争与任务设置重构在切换加工过程中的关系,以切换代价为指标,研究了刺激类型与预先信息对任务切换的影响效应,结果发现:(1)无信息的切换代价显著高于部分信息和全部信息的切换代价,而后二者之间无显著差异;(2)单向刺激的切换代价显著高于双向刺激的切换代价;(3)预先信息和刺激类型对切换代价的影响无交互作用。这表明任务设置重构与联结竞争是两个具有相加效应的序列认知活动。     

Task switching based on externally presented versus internally generated information

A number of observations from the task switching literature suggest that task preparation based on internally generated knowledge is less efficient than task preparation based on externally presented information. In the present study, we investigated task switching based on internally generated versus externally presented information and additionally varied the reliability of foreknowledge. Source and reliability of foreknowledge were varied between groups of participants. With reliable foreknowledge, the relevant task always conformed to foreknowledge, even when the features of the imperative stimulus called for an alternative task. With unreliable foreknowledge, the relevant task was determined by the imperative stimulus and foreknowledge was sometimes misleading. Apart from measuring switch costs, we examined the effectiveness of establishing a task set by measuring interference exerted by conflicting stimuli (conditions with reliable foreknowledge) or misled expectancies (conditions with unreliable foreknowledge). In terms of switch costs, we observed a slight superiority of externally presented over internally generated information when foreknowledge was reliable, but this relationship strongly reversed with unreliable foreknowledge. This conclusion was corroborated by observations regarding the effectiveness of task-set establishment in terms of proneness to interference.

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Effects of repetition and foreknowledge in task-set reconfiguration

To examine the roles of executive control and automatic activation in task switching, we manipulated foreknowledge as well as task transitions. In Experiments 1 and 2, performance with foreknowledge was faster than performance with no foreknowledge, but the amount of switch cost did not depend on foreknowledge. This result suggests that switch costs primarily reflect persisting activation rather than inadequate preparation. In Experiment 3, switch cost was greater with foreknowledge about task transition alone than with foreknowledge about both task transition and identity, suggesting that foreknowledge about specific task identity did allow preparation for a switched task. We argue that task repetition and foreknowledge effects are independent. Although foreknowledge allows preparation for both repeated and switched tasks, repeating the same task has benefits over task switching regardless of foreknowledge.     

Exogenous influences on task set activation in task switching

To explore the effect of exogenous processes on cognitive control, we used a cueing task-switching paradigm with two spatial judgement tasks and added an irrelevant colour attribute to the task-relevant spatial attribute of the target. The colour was not related to any specific Stimulus–Response relation in the tasks. A correlation was created between stimulus colour and task identity. This correlation was strong but imperfect in Experiment 1 and perfect in Experiment 2. As a result of the colour–task correlation, stimuli contained redundant information about task identity. By changing the correlation pattern every few blocks we caused this information to be sometimes invalid. In both experiments, performance was worse when the information carried by the target was invalid than when it was valid. However, this effect was exclusive to conditions with short task preparation time. By comparing performance with a control group, which had no colour–task correlation (in Experiment 2) we established that the colour manipulation did not cause a qualitative change in preparation strategy, and that the exogenous effect was stronger in switch trials than in repetition trials. We conclude that exogenous processes that are related to task set affect performance primarily if they are presented before endogenous processes of task set preparation have been launched.     

Control processes in voluntary and explicitly cued task switching

Explicitly cued task switching slows performance relative to performing the same task on consecutive trials. This effect appears to be due partly to more efficient encoding of the task cue when the same cue is used on consecutive trials and partly to an additional task-switching process. These components were examined by comparing explicitly cued and voluntary task switching groups, with external cues presented to both groups. Cue-switch effects varied in predictable ways to dissociate explicitly cued and voluntary task switching, whereas task-switch effects had similar characteristics for both instructional groups. The data were well fitted by a mathematical model of task switching that included a cue-encoding mechanism (whereby cue repetition improves performance) and an additional process that was invoked on task-switch trials. Analyses of response-time distributions suggest that this additional process involves task-set reconfiguration that may or may not be engaged before the target stimulus is presented.     

An imperfect relationship between prospective memory and the prospective interference effect

Three experiments examined the functional relationship between the frequency of prospective responding and the prospective interference effect within the context of a task switching paradigm. Prospective responding was less frequent across the experiments when prospective cues appeared in switch blocks than when they appeared in pure blocks. The magnitude of the prospective interference effect for response time (RT) was similar for pure and switch blocks when exogenous task cuing was used, and was greater for switch blocks than for pure blocks when endogenous task cuing was used. These data reveal a dissociation between the effect of task switching on the frequency of prospective responding and the prospective interference effect, and indicate that the functional relationship between these two measures is dependent on task demands.     

任务切换理论争议新证据

任务切换是研究认知控制的主要范式之一。大量研究发现切换试次比重复试次的反应时更长,错误率更高,这种差异称为切换代价。任务切换时所产生切换代价的理论解释主要有惯性论、重构论和联结论。近十年来,这些理论均获得新的实验支持和发展,但其争议依旧,没有哪一理论能成功解释任务切换的所有效应。未来研究可以建立整合模型,以准确描述切换代价产生的认知机制。     

Task preparation and task repetition: two-component model of task switching.

The switch cost (the disadvantage of performing a new task vs. a repeated task) has been attributed to lack of preparation for the switched task or priming of the repeated task. These sources were examined by manipulating foreknowledge of task transition (repeat or switch), response-to-stimulus interval (RSI), and practice level. Regardless of foreknowledge, the cost decreased with RSI and practice. The reduction was greater with foreknowledge than with no foreknowledge, and the amount of switch cost did not depend on foreknowledge. These results suggest that the switch cost with foreknowledge may consist of both inadequate preparation and repetition benefit but the switch cost with no foreknowledge may reflect repetition benefit only. An ACT-R (adaptive control of thought-rational) model was proposed, accommodating both preparation and priming effect with 2 independent processes: conflict resolution among productions and decay of chunk activation.