Cueing task goals and earning money: Relatively high monetary rewards reduce failures to act on goals in a Stroop task

We examined the role of monetary rewards in failures to act on goals in a Stroop task. Based on recent developments in theorizing on the interplay between rewards and cognitive control, we hypothesized that relatively high monetary rewards enhance the focus and stability of a cued task goal compared to low monetary rewards, and hence cause a reduction in failures to act on current task goals under circumstances that warrant top–down goal implementation. To test this, participants received a modified version of the Stroop task, in which they were either briefly cued with the goal of naming the color or meaning of targets on a trial-by-trial basis. After goal cuing, but before presenting the target, either a low or high reward cue was presented. Results showed that higher rewards produced a general speed-up. More importantly, Stroop interference on error rates was lower in the high reward condition compared to the low reward condition, revealing that the rewards enhanced focus and stability of the cued goal. These results provide support for theorizing that reward processing modulates utility assessment of current goals by affecting attention to facilitate goal-directed behavior.     

Reward prospect interacts with trial-by-trial preparation for potential distraction

When attending for impending visual stimuli, cognitive systems prepare to identify relevant information while ignoring irrelevant, potentially distracting input. Recent work showed that a supramodal distracter-filtering mechanism is invoked in blocked designs involving expectation of possible distracter stimuli, although this entails a cost (distraction-filtering cost) on speeded performance when distracters are expected but not presented. Here we used an arrow-flanker task to study whether an analogous cost, potentially reflecting the recruitment of a specific distraction-filtering mechanism, occurs dynamically when potential distraction is cued trial-to-trial (cued distracter-expectation cost). In order to promote the maximal utilization of cue information by participants, in some experimental conditions the cue also signalled the possibility of earning a monetary reward for fast and accurate performance. This design also allowed us to investigate the interplay between anticipation for distracters and anticipation of reward, which is known to engender attentional preparation. Only in reward contexts did participants show a cued distracter-expectation cost, which was larger with higher reward prospect and when anticipation for both distracters and reward were manipulated trial-to-trial. Thus, these results indicate that reward prospect interacts with the distracter expectation during trial-by-trial preparatory processes for potential distraction. These findings highlight how reward guides cue-driven attentional preparation.     

Learning grammatical categories from distributional cues: Flexible frames for language acquisition

Performance in a behavioral task can be facilitated by associating stimulus properties with reward. In contrast, conflicting information is known to impede task performance. Here we investigated how reward associations influence the within-trial processing of conflicting information using a color-naming Stroop task in which a subset of ink colors (task-relevant dimension) was associated with monetary incentives. We found that color-naming performance was enhanced on trials with potential-reward versus those without. Moreover, in potential-reward trials, typical conflict-induced performance decrements were attenuated if the incongruent word (task-irrelevant dimension) was unrelated to reward. In contrast, incongruent words that were semantically related to reward-predicting ink colors interfered with performance in potential-reward trials and even more so in no-reward trials, despite the semantic meaning being entirely task-irrelevant. These observations imply that the prospect of reward enhances the processing of task-relevant stimulus information, whereas incongruent reward-related information in a task-irrelevant dimension can impede task performance.     

奖赏预期对面孔情绪加工的影响：一项事件相关电位研究

采用事件相关电位(ERPs)技术考察了奖赏预期对人类面孔情绪识别的影响。实验采用线索-目标范式, 分别记录了被试在奖赏预期条件下以及无奖赏预期条件下对正性、中性和负性面孔进行情绪辨别任务的ERP数据。行为结果显示, 被试在奖赏预期条件下的反应时快于无奖赏预期条件下的反应时, 对情绪面孔的反应时快于对中性面孔的反应时。ERPs数据显示, 奖赏线索比无奖赏线索诱发了更正的P1、P2和P300成分。目标刺激诱发的P1、N170波幅以及N300均受到奖赏预期的调节, 在奖赏预期条件下目标诱发了更正的ERPs。P1、N170、VPP等成分没有受到面孔情绪的影响, 而额中央位置的N300波幅显示情绪(正性与负性)面孔与中性面孔加工的差异。重要的是, N300波幅出现奖赏预期与情绪的交互作用, 正、负情绪加工效应以及负性偏向效应受奖赏预期的差异性影响。正性情绪加工效应不受奖赏预期的影响, 而负性情绪加工效应和负性偏向效应在奖赏预期条件下显著大于无奖赏预期条件下。这些结果说明, 奖赏预期能够调节对面孔情绪的加工, 且不同加工进程中奖赏对情绪加工的调节作用不同。动机性信息调节注意资源的分配, 促进了个体在加工面孔情绪时的负性偏向。     

Reward-driven modulation of adaptive control: How prospective monetary gains interact with unpredictable control demands

Shifting attention is an effortful control process and incurs a cost on the cognitive system. Previous research suggests that rewards, such as monetary gains, will selectively enhance the ability to shift attention when this demand for control is explicitly cued. Here, we hypothesized that prospective monetary gains will selectively enhance the ability to shift attention even when control demand is unpredictable and not cued beforehand in a modality shift paradigm. In two experiments we found that target detection was indeed facilitated by reward signals when an unpredictable shift of attention was required. In these crossmodal trials the target stimulus was preceded by an unpredictive stimulus directing attention to the opposite modality (i.e., visual–auditory or auditory–visual). Importantly, there was no reward effect in ipsimodal trials (i.e., visual–visual or auditory–auditory). Furthermore, the absence of the latter effect could not be explained in terms of physical limits in speed of responding. Potential motivation of monetary rewards thus selectively translates into motivational intensity when control (i.e., switching) is demanded in unpredictable ways.     

Brain regions activated by endogenous preparatory set shifting as revealed by fMRI

An ongoing controversy concerns whether executive control mechanisms can actively reconfigure the cognitive system in preparation for switching to a new task set. To address this question, we recorded brain activity from 14 healthy participants, using event-related functional magnetic resonance imaging, while they performed a cued attention task. Critically, in any particular trial, the cued task set was either the same as that in the previous trial or switched. As was hypothesized, cue-related, switch-specific preparatory activity was observed in a network of dorsal frontal and parietal brain areas that are typically associated with cognitive control processes. Moreover, the magnitude of switch-specific preparatory activity varied with the number of possible task sets that could be presented in a given trial block. These findings provide compelling support for the existence of top-down, preparatory control processes that enable set switching. Furthermore, they demonstrate that global task structure is a critical determinant of whether switch-specific preparatory activity is observed.     

Monetary reward increases attentional effort in the flanker task

An important question is whether monetary reward can increase attentional effort in order to improve performance. Up to now, evidence for a positive answer is weak. Therefore, in the present study, the flanker task was used to examine this question further. Participants had to respond sooner than a certain deadline in a flanker task. One group of participants received a performance-contingent monetary reward, whereas the other group earned a fixed amount of money. As a result, monetary reward significantly improved performance in comparison with the control group. The analysis of speed-accuracy trade-off functions revealed that monetary reward increased attentional effort, leading to an enhanced quality of stimulus coding. Little evidence was found that reward also improved selective spatial attention.     

Approach and avoidance movements are unaffected by cognitive conflict: A comparison of the Simon effect and stimulus–response compatibility

Participants in this study reached from central fixation to a lateral position that either contained or was opposite to the stimulus. Cognitive conflict was induced when the stimulus and response directions did not correspond. In the Simon task, the response direction was cued by the color of the lateral stimulus, and corresponding and noncorresponding trials varied randomly in the same block of trials, resulting in high uncertainty and long reaction times (RTs). In the stimulus-response compatibility (SRC) task, participants reached toward or away from the stimulus in separate blocks of trials, resulting in low uncertainty and short RTs. In the SRC task, cognitive conflict in noncorresponding trials slowed down RTs but hardly affected reach trajectories. In the Simon task, both RTs and reach trajectories were strongly influenced by stimulus-response correspondence. Despite the overall longer RTs in the Simon task, reaches were less direct and deviated toward the stimulus in noncorresponding trials. Thus, cognitive conflict was resolved before movement initiation in the SRC task, whereas it leaked into movement execution in the Simon task. Current theories of the Simon effect, such as the gating of response activation or response code decay, are inconsistent with our results. We propose that the SRC task was decomposed as approaching and avoiding the stimulus, which is sustained by stereotyped visuomotor routines. With complex stimulus-response relationships (Simon task), responses had to be coded as leftward and rightward, with more uncertainty about how to execute the action. This uncertainty permitted cognitive conflict to leak into the movement execution.     

Impaired color word processing at an unattended location: Evidence from a Stroop task combined with inhibition of return

A Stroop task with separate color bar and color word stimuli was combined with an inhibition-of-return procedure to examine whether visual attention modulates color word processing. In Experiment 1, the color bar was presented at the cued location and the color word at the uncued location, or vice versa, with a 100- or 1,050-msec stimulus onset asynchrony (SOA) between cue and Stroop stimuli. In Experiment 2, on Stroop trials, the color bar was presented at a central fixated location and the color word at a cued or uncued location above or below the color bar. In both experiments, with a 100-msec SOA, the Stroop effect was numerically larger when the color word was displayed at the cued location than when it was displayed at the uncued location, but with the 1,050-msec SOA, this relation between Stroop effect magnitude and location was reversed. These results provide evidence that processing of the color word in the Stroop task is modulated by the location to which visual attention is directed.     

Attention, temporal predictability, and the time course of context effects in naming performance

Models of attention and context effects in naming performance should be able to account for the time course of color-word Stroop interference revealed by manipulations of the stimulus onset asynchrony (SOA) between color and word. Prominent models of Stroop task performance ( [Cohen et al., 1990], [Cohen and Huston, 1994] and [Phaf et al., 1990]) fail to account for the fact that response time (RT) and Stroop interference peak at zero SOA and diminish with word preexposure. The models may be saved by assuming that the time course of interference is determined by a strategic orienting of attention to color onsets when SOA is predictable. To test this temporal predictability hypothesis, SOA was blocked or randomly mixed in Experiment 1. In addition, the time interval between color onsets was randomly variable in Experiment 2. Although RTs were affected, none of the randomization manipulations influenced the typical shape of the time course of Stroop effects. These findings provide evidence against the temporal predictability hypothesis and thereby against prominent models of the Stroop task.     

A parallel distributed processing model of stimulus-stimulus and stimulus-response compatibility.

A parallel distributed processing (PDP) model is proposed to account for choice reaction time (RT) performance in diverse cognitive and perceptual tasks such as the Stroop task, the Simon task, the Eriksen flanker task, and the stimulus-response compatibility task that are interrelated in terms of stimulus-stimulus and stimulus-response overlap (Kornblum, 1992). In multilayered (input-intermediate-output) networks, neuron-like nodes that represent stimulus and response features are grouped into mutually inhibitory modules that represent stimulus and response dimensions. The stimulus-stimulus overlap is implemented by a convergence of two input modules onto a common intermediate module, and the stimulus-response overlap by direct pathways representing automatic priming of outputs. Mean RTs are simulated in various simple tasks and, furthermore, predictions are generated for complex tasks based on performance in simpler tasks. The match between simulated and experimental results lends strong support for our PDP model of compatibility.     

RT distributional analysis of cognitive-control-related brain activity in first-episode schizophrenia

Impairments in cognitive control are a defining feature of schizophrenia. Aspects of cognitive control include proactive control—the maintenance of task rules or goals to bias attention and maintain preparedness—and reactive control—the engagement of attention in reaction to changing cognitive demands. Proactive control is thought to be particularly impaired in schizophrenia. We sought to examine proactive and reactive control in schizophrenia, as measured by reaction time (RT) variability, and especially long RTs, which are thought to represent lapses in proactive control, during the Stroop paradigm. Furthermore, we sought to examine the neural underpinnings of lapses in proactive control and the subsequent engagement of reactive control in those with schizophrenia, as compared to healthy controls, using fMRI. We found that patients with schizophrenia displayed greater RT variability and more extremely long RTs than controls suggesting that proactive control was weaker in the schizophrenia than in the control group. All of the subjects engaged regions of the cognitive control network during long RTs, consistent with an engagement of reactive control following a failure in proactive control on these trials. The schizophrenia group, however, displayed significantly diminished activity in these regions relative to controls. Our results suggest increased failures in proactive control, but also impaired reactive control, in schizophrenia as compared to healthy subjects.     

Computerized stroop test to assess selective attention in children with attention deficit hyperactivity disorder

Research shows abnormal function of the pre-frontal cortex in Attention Deficit Hyperactivity Disorder (ADHD). This cortex is involved in the control of executive functions related to planning and execution of goal-oriented strategies, working memory, inhibitions, cognitive flexibility, and selective attention. Selective attention involves focus on the target stimulus, ignoring competing distractions. The Stroop Test (Stroop, 1935) is usually used to evaluate selective attention. This study investigated whether children with ADHD could exhibit modified performance in the Stroop Test. Using a computerized version of this test (Capovilla, Montiel, Macedo, & Charin, 2005), the study compared the reaction times (RTs) of 62 Brazilian children, between 8 and 12 years of age, 31 of whom were diagnosed with ADHD and sent to psychiatric clinics, and 31 without ADHD studying in regular schools. All children with ADHD satisfied the criteria of the DSM-IV-TR and were evaluated with the Conners Abbreviated Questionnaire (Goyette, Conners, & Ulrich, 1978), completed by parents and teachers. The results revealed that children with ADHD exhibit greater interference in RT than children without ADHD. This corroborated the hypothesis that children with ADHD exhibit a deficit in selective attention, consisting in augmented RTs, as measured by the Computerized Stroop Test.     

The effects of different instructions for preparatory muscle tension on simple reaction time

The effects of preparatory weak muscular contraction (pre-tension) have been investigated in a number of previous studies using tasks with either simple or choice responses to measure the reaction time (RT). These studies suggested that optimal pre-tension performed prior to a motor response tends to shorten the RTs. Using a simple RT task in which participants performed a grip response to a visual stimulus, the present study compared the RTs between two pre-tension conditions (self-selection and constraint) to investigate the effects of different instructions for pre-tension. Under the self-selection condition, participants were asked to determine their optimal pre-tension levels while attempting to give responses as fast as possible. Under the constraint condition, the participants developed a pre-tension at a target force determined by the experimenter. The target force was set at the same level as the pre-tension level maintained under the self-selection. Despite the fact that the pre-tension level manipulated was the same for both conditions, the RTs were significantly shorter under self-selection than under constraint. Moreover, the present study showed a positive correlation coefficient between the proportion of shortening in RT and the variation of pre-tension level. This indicated a performance trade-off between the stability of pre-tension and RTs. The result suggests that shorter RTs that occur under self-selection are primarily mediated by mental factors, such as attention allocation, rather than by the effects of peripheral muscular preparation.     

Preparatory Set,Response Complexity,and Reaction Latency

The interaction between preparatory set and response complexity was demonstrated in an experiment investigating the reaction latency of discrete arm movements. Following simple finger-lift reaction-time (RT) trials, subjects performed simple and complex versions of a discrete horizontal arm movement under one of two enforced preparatory set conditions. For the simple task, requiring subjects to attend to the components of the response prior to stimulus presentation (enforced motor set) produced significantly shorter RTs than when concentration was on the stimulus (enforced sensory set). However, RT differences for the complex version of the task failed significance. Theoretical implications of the results for Henry’s (1960) memory drum theory of neuromotor reaction were discussed.     

A facilitative effect of negative affective valence on working memory

Gotoh, F., Kikuchi, T. &Olofsson, U. (2010). A facilitative effect of negative affective valence on working memory. Scandinavian Journal of Psychology, 51, 185–191. Previous studies have shown that negatively valenced information impaired working memory performance due to an attention‐capturing effect. The present study examined whether negative valence could also facilitate working memory. Affective words (negative, neutral, positive) were used as retro‐cues in a working memory task that required participants to remember colors at different spatial locations on a computer screen. Following the cue, a target detection task was used to either shift attention to a different location or keep attention at the same location as the retro‐cue. Finally, participants were required to discriminate the cued color from a set of distractors. It was found that negative cues yielded shorter response times (RTs) in the attention‐shift condition and longer RTs in the attention‐stay condition, compared with neutral and positive cues. The results suggest that negative affective valence may enhance working memory performance (RTs), provided that attention can be disengaged.     

Trunk orientation induces neglect-like lateral biases in covert attention

The purpose of this study was to resolve a paradox in the literature on the effects of body orientation on spatial attention. Neuropsychological studies have found that real or simulated trunk rotation relieves contralesional inattention in patients with unilateral neglect, suggesting that trunk orientation affects how attention is allocated to space. However, in two previous studies, trunk orientation did not affect spatial attention in other populations. In this study, we investigated the effects of trunk orientation on the performance of a covert attention task by neurologically intact adults. The covert attention task allowed the evaluation of the effects of trunk orientation on both the allocation of attention to space and the ability to shift that attention to new locations. As in previous research, trunk orientation did not affect participants' response times (RTs) to validly cued targets. However, rotating participants' trunks to the left increased their RTs to invalidly cued targets on the right and decreased their RTs to invalidly cued targets on the left. These results indicate that trunk orientation induces directional biases in the ability to shift attention. Thus, for intact participants, trunk rotation created lateral biases in the covert attention task similar to those seen in neglect patients.     

Selective impairment of auditory selective attention under concurrent cognitive load

Load theory predicts that concurrent cognitive load impairs selective attention. For visual stimuli, it has been shown that this impairment can be selective: Distraction was specifically increased when the stimulus material used in the cognitive load task matches that of the selective attention task. Here, we report four experiments that demonstrate such selective load effects for auditory selective attention. The effect of two different cognitive load tasks on two different auditory Stroop tasks was examined, and selective load effects were observed: Interference in a nonverbal-auditory Stroop task was increased under concurrent nonverbal-auditory cognitive load (compared with a no-load condition), but not under concurrent verbal-auditory cognitive load. By contrast, interference in a verbal-auditory Stroop task was increased under concurrent verbal-auditory cognitive load but not under nonverbal-auditory cognitive load. This double-dissociation pattern suggests the existence of different and separable verbal and nonverbal processing resources in the auditory domain.     

色-词Stroop任务中的冲突类型述评

在认知控制领域中, 色-词Stroop任务常被用于研究冲突加工的内在机制。本文首先简述色-词Stroop任务中的刺激冲突和反应冲突及研究这两类冲突常用的实验范式。然后介绍这两类冲突的神经动力学特征：事件相关电位研究显示, N450的波幅调整反映了大脑对冲突的监测, 持续电位(sustained potential, SP)的波幅调整反映了大脑对反应冲突的解决; 核磁共振成像研究显示, 前扣带回、背外侧前额叶分别在反应冲突的监测、认知控制的执行上扮演着重要的角色。文章最后针对目前研究范式存在的问题提出了改进方法和认知神经研究的新方向。     

The Stroop effect at 80: The competition between stimulus control and cognitive control

For more than 80 years, researchers have examined the interference between automatic processing of stimuli, such as the meaning of color words, on performance of a controlled‐processing task such as naming the color in which words are printed. The Stroop effect and its many variations provide an ideal test platform for examining the competition between stimulus control and cognitive control of attention, as reflected in behavior. The two experiments reported here show that rhesus monkeys, like human adults, show interference from incongruous stimulus conditions in a number‐Stroop task, and that the monkeys may be particularly susceptible to influence from response strength and less able, relative to human adults, of using executive attention to minimize this interference.