数学优差生任务转换中的准备效应

采用任务转换范式考察144名数学优差生任务转换中的准备效应.结果发现:延长反应-线索间距和线索-目标间距都减小了转换代价,表明任务定势惯性和任务定势重组都起作用;学优生监控当前目标的同时选择任务表征的能力,以及激活新任务定势的同时抑制先前任务定势的能力都比学差生强;反应定势选择和反应定势转换能力从8岁到18岁都逐渐增强.     

不同熟练度双语者非语言任务转换的差异——来自ERP证据

考察熟练蒙汉双语者和非熟练汉英双语者在非语言任务转换中优势效应的脑电活动特征。采用线索任务2:1转换范式,通过操纵线索到刺激间的时间间隔,比较熟练双语者与非熟练双语者在不同时间间隔的转换代价减小效应,探索转换能力的优势效应是否源于内源性准备。研究结果显示:熟练双语者在线索到刺激间的时间间隔为250 ms时反应时和转换代价都显著小于非熟练双语者;熟练双语者在线索到刺激间的时间间隔从0 ms到250 ms的转换代价减小效应更大。脑电数据结果显示:无论转换序列还是重复序列,非熟练双语者的D-Pos的平均波幅均比熟练双语者更正,说明非熟练双语者需要更多的心理资源进行重构准备。研究提示不同语言的转换经验促进了熟练双语者执行功能的转换能力,这种转换能力的优势效应可迁移到相似的非语言任务转换过程中。     

材料类型和任务可预测性在任务转换中的作用

以阿拉伯数字和汉字数字为材料,采用奇偶判断和大小判断任务交替呈现范式,考察材料类型和任务可预测性在任务转换中的作用。结果发现:(1)对阿拉伯数字和汉字数字的反应时无显著差异,转换代价差异不显著;(2)不可预测任务反应时显著长于可预测任务,转换任务和重复任务都显示了基于可预测性的准备效应。表明材料类型对任务转换无影响,重复和转换任务都存在一般的任务控制更新过程。     

自主任务转换中的重构和干扰

任务转换是研究执行功能的常用范式。任务转换通常伴随着转换代价：执行转换任务比重复任务的反应时更长、错误率更高。转换代价可能反映了任务设置重构(重构理论), 也可能表明任务之间存在干扰(干扰理论)。与任务线索范式相比, 自主任务转换范式更具生态效度, 而且不仅能获得转换代价这个传统结果, 还引入了任务选择比例、任务转换率等新指标, 其结果倾向于支持重构理论。此外, 新近研究指出自主任务转换可能也包含干扰的作用。未来, 应通过进一步改进实验范式等方法, 实现两大理论的融合。     

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     

语言转换的认知及其神经机制

语言转换是双语研究领域的焦点问题之一,抑制控制模型、语言特异性选择模型、任务设置惯性模型和序列难度效应模型从不同的角度解释了语言转换的认知机制。认知神经科学的一些研究发现,语言转换与任务转换具有类似的神经机制,说明语言转换代价与任务转换代价的本质可能是相同的。抑制控制和语言熟练程度如何影响语言的转换,语言转换代价与任务转换代价的本质是否相同,一般领域的抑制机制是否可以迁移到语言转换领域等问题是未来需要进一步研究的问题。     

工作记忆中转换加工的内源性准备 和外源性调节

考察工作记忆中转换加工的控制过程。采用“任务转换”范式,探究预知条件（实验一）和未预知条件（实验二）下的转换加工。结果发现：（1）任务重复与任务转换是两个不同的过程;无论是在预知条件还是未预知条件下都出现任务重复效应显著大于任务转换效应;（2）验证了转换加工包括内源性准备和外源性调节两个不同的加工过程, 内源性准备只是任务设置重建的一部分;（3）对先后呈现的两个任务（任务1—任务2 ：任务重复或任务转换）在预知重复、预知转换和未预知条件下,任务2对任务1的影响不同,存在前瞻性记忆效应。由此推断转换加工的心理过程是：在预知情况下,任务1呈现后即启动内源性准备,直到任务2呈现时,通过外源性调节最终完成任务转换;而在未预知情况下,只能依赖外源性调节来实现     

多感觉整合范式中潜在的跨通道转换效应

大脑可以对来自不同感觉通道的信息进行处理与整合。与单一感觉通道相比, 个体对同时呈现在不同感觉通道的目标信号的响应会更快。对于这种现象的一种主要理论解释是共同激活模型, 该模型认为来自不同通道的刺激在特定的脑区汇聚整合, 比如顶叶内沟、颞上沟和前额叶皮层区域。整合后的信号强度更大, 可以更快地触发反应, 但是信号的整合发生在认知加工的哪一阶段目前尚未有明确结论。当个体对出现在不同感觉通道之间的任务转换进行加工时, 产生与感觉通道相关的任务转换的损失小于跨感觉通道转换损失与任务转换损失的总和, 这为与感觉通道相关的转换代价来源于任务设置的惯性和干扰提供了证据。而在单通道和多通道之间发生转换时, 跨通道转换代价会减小甚至消失, 这是由于同时发生的多感觉整合抵消了一部分损失, 这种现象支持了共同激活模型理论。然而, 多感觉信号整合对任务转换的神经加工过程产生怎样的影响并不清楚, 在未来的研究中可以把多感觉整合范式同经典的任务转换范式结合改进, 进而确定跨通道转换的加工机制和多感觉信号整合的发生阶段。     

任务难度对焦点转换和焦点内信息激活的影响

设置两种难度的比较任务(倒序数2和数3)和一个探测任务(倒序数1),探讨:(1)排除Voigt等研究中数字启动效应后,任务难度对焦点转换的影响;(2)任务难度对焦点内信息激活的影响.结果表明:(1)ft务难度影响焦点转换代价,即任务越难,焦点转换代价越大;(2)任务难度影响焦点内信息激活水平,即任务越难,激活水平越低.这提示:任务难度对焦点转换的影响是多方面的.     

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     

Short cue presentations encourage advance task preparation: a recipe to diminish the residual switch cost

In the task-switching literature, it has frequently been demonstrated that although advance task preparation reduces the switch cost, it never really eliminates the switch cost. This remaining residual switch cost received much attention, and it has been argued that advance preparation is restricted in nature. In the present study, the role of task-cue presentation in the establishment of the residual switch cost was investigated. In 4 experiments, the cue was removed during the preparation interval, and it was hypothesized that this would encourage participants to complete advance task preparation. The results of all 4 experiments provided support for this hypothesis: When the cue was presented for a short time and then removed, the residual switch cost completely disappeared. This was found for different cue types. Furthermore, Experiment 3 demonstrated that it was not the presence of the cue itself but merely differences in advance task preparation that caused the effects. This suggests that advance task preparation is not as restricted in nature as previously assumed.     

Task practice differentially modulates task-switching performance across the adult lifespan

Cued-trials task-switching paradigms have been used extensively to examine ageing-related changes in cognitive control. Many studies report an increase in mixing cost (i.e., cost of repeating the same task in a single-task vs. a mixed-task block) and a less reliable increase in switch cost (i.e., cost of switching vs. repeating tasks in a mixed-task block) in old as compared to young adults. However, there is substantial variability between studies in the emergence and size of age effects on mixing and/or switch cost. In this study, we examined variation in mixing cost and switch cost as a function of task practice and preparation interval across the adult lifespan (18-79 years) using a paradigm that promotes advance preparation and reduces cue encoding differences between switch and repeat trials. Both preparation interval and task practice modulated mixing cost and switch cost-but task practice mediated the effects of preparation interval and age differentially for mixing cost and switch cost. Mixing cost was consistently larger in older participants, reduced with preparation and varied little with task practice. In contrast, the effect of preparation interval on switch cost varied with task practice. Reduction in switch cost with preparation interval emerged in younger participants by the second practice session and even later in older participants. When fully practiced, older participants showed greater mixing cost but less switch cost than younger participants. Age effects on both mixing cost and switch cost were mediated by changes in processing of repeat trials, indicative of reduced differentiation between switch and repeat trials in mixed-task blocks. This is consistent with reduced cognitive flexibility with increasing age.     

No-go trials can modulate switch cost by interfering with effects of task preparation

It has recently been shown that the cost associated with switching tasks is eliminated following ‘no-go’ trials, in which response selection is not completed, suggesting that the switch cost depends on response selection. However, no-go trials may also affect switch costs by interfering with the effects of task preparation that precede response selection. To test this hypothesis we evaluated switch costs following standard go trials with those following two types of non-response trials: no-go trials, for which a stimulus is presented that indicates no response should be made (Experiment 1); and cue-only trials in which no stimulus is presented following the task cue (Experiment 2). We hypothesized that eliminating no-go stimuli would reveal effects of task preparation on the switch cost in cue-only trials. We found no switch cost following no-go trials (Experiment 1), but a reliable switch cost in cue-only trials (i.e., when no-go stimuli were removed; Experiment 2). We conclude that no-go trials can modulate the switch cost, independent of their effect on response selection, by interfering with task preparation, and that the effects of task preparation on switch cost are more directly assessed by cue-only trials.     

Modeling task switching without switching tasks: a short-term priming account of explicitly cued performance

Switch costs in task switching are commonly attributed to an executive control process of task-set reconfiguration, particularly in studies involving the explicit task-cuing procedure. The authors propose an alternative account of explicitly cued performance that is based on 2 mechanisms: priming of cue encoding from residual activation of cues in short-term memory and compound cue retrieval of responses from long-term memory. Their short-term priming account explains the repeated cue encoding benefit, switch cost, reduction in switch cost with preparation time, and other effects. The authors develop a mathematical model of their priming account and fit it to data from 3 experiments, demonstrating that a set of basic psychological processes can produce several effects--including putative switch costs--without switching tasks.     

Component processes in task switching

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.     

Task-switching performance with 1:1 and 2:1 cue-task mappings: not so different after all

When task-switching studies use the task-cuing procedure with a 1:1 cue-task mapping, task switching and cue switching are confounded, which is problematic for interpreting switch costs. The use of a 2:1 cue-task mapping is a potential solution to this problem, but it is possible that introducing more cues may also introduce marked changes in task-switching performance. In 5 experiments involving 160 subjects, the authors compared performance with 1:1 and 2:1 mappings across several methodological changes. Differences in switch costs between mappings were small and, in most analyses, nonsignificant. In all experiments, both mappings yielded significant reductions in switch cost across cue-target interval, and there were significant cue-switching effects with the 2:1 mapping. A model of cue encoding fit the data from both mappings about equally well. Overall, task-switching performance was more similar than it was different between mappings, leading the authors to suggest that the use of a 2:1 mapping is a viable solution to the problem associated with a 1:1 mapping.     

Dissociating the components of switch cost using two-to-two cue-task mapping

In the task switch paradigm, a switch of task is typically accompanied by a change in task cue. It has been proposed that the performance deficit usually observed when switching tasks is actually the result of changing cues. To test this possibility, we used a 2:2 cue-task mapping in which each cue indicated 2 different tasks. With advance presentation of a cue, the cost associated with changing cues disappeared, though a substantial task switch cost remained. Without advance cues, the relative contributions of task switch cost and cue change cost differed by transition frequencies. The results suggest that task execution contributes to switch cost independent of cue changes.     

策略转换的成本与顺序效应

灵活的策略转换是个体有效地解决问题的重要条件。策略转换需要成本已得到大量证明,但策略转换成本是否为对称转换成本尚无定论。基于已有研究,对策略转换中存在策略顺序困难效应与较差策略顺序调节效应两种典型的顺序效应进行了具体介绍。在此基础上提出了不对称策略转换成本可能是对称转换成本与策略顺序困难效应之和的假设,并进而提出设想:可通过操纵时间变量来分离策略顺序困难效应与较差策略顺序调节效应。此外,从策略转换成本的角度创新地阐释了策略选择的惰性与倒退现象。     

汉、英句法结构相似性与第二语言的熟练度对第二语言句法加工的影响

采用事件相关电位（ERP）技术,考察了汉、英句法结构相似性与第二语言（英语）熟练度对第二语言句法加工的影响。实验材料包含与汉语句法结构相似和不同的两种英语句法结构违反的句子。结果发现：与正确句子相比,相似句法违反句在高熟练组被试中,引发正向的ERP波形偏转（150-800ms）,而在低熟练组被试中,只引发了降低的N400（300-550ms）效应;对于不同句法违反句,无论高低熟悉程度的被试,均未出现显著的ERP效应。研究结果表明,第二语言句法与母语的相似性越高,加工起来更容易;第二语言熟练度水平对第二语言句法加工具有一定的促进作用,但受到两种语言句法结构相似性的影响,相似性越高,熟练度的促进作用越大。