Evidence for a cognitive control network for goal-directed attention in simple sustained attention

The deterioration of performance over time is characteristic for sustained attention tasks. This so-called “performance decrement” is measured by the increase of reaction time (RT) over time. Some behavioural and neurobiological mechanisms of this phenomenon are not yet fully understood. Behaviourally, we examined the increase of RT over time and the inter-individual differences of this performance decrement. On the neurophysiological level, we investigated the task-relevant brain areas where neural activity was modulated by RT and searched for brain areas involved in good performance (i.e. participants with no or moderate performance decrement) as compared to poor performance (i.e. participants with a steep performance decrement). For this purpose, 20 healthy, young subjects performed a carefully designed task for simple sustained attention, namely a low-demanding version of the Rapid Visual Information Processing task. We employed a rapid event-related functional magnetic resonance imaging (fMRI) design. The behavioural results showed a significant increase of RT over time in the whole group, and also revealed that some participants were not as prone to the performance decrement as others. The latter was statistically significant comparing good versus poor performers. Moreover, high BOLD-responses were linked to longer RTs in a task-relevant bilateral fronto-cingulate-insular-parietal network. Among these regions, good performance was associated with significantly higher RT-BOLD correlations in the pre-supplementary motor area (pre-SMA). We concluded that the task-relevant bilateral fronto-cingulate-insular-parietal network was a cognitive control network responsible for goal-directed attention. The pre-SMA in particular might be associated with the performance decrement insofar that good performers could sustain activity in this brain region in order to monitor performance declines and adjust behavioural output.     

Division of attention: The single-channel hypothesis revisited

Two experiments are reported in which subjects performed two forced-paced serial reaction time tasks separately and together at their maximum sustainable rates of information processing. Experiment 1 investigated the effects on the relationship between single- and dual-task performance of using tasks with the same or different input and output modality characteristics; an additional condition tested the effects on this relationship of using tasks with higher S-R compatibility. Experiment 2 investigated the effects on the relationship between single- and dual-task performance of varying information load (number of S-R alternatives). No significant differences were found in subjects' capacities to process information in single- and dual-task conditions. This finding was unaffected by: (a) the absolute information levels of the tasks, (b) whether inputs and/or outputs involved the same or different modalities, or (c) the level of S-R compatibility. The data from both experiments provide strong support for the single-channel hypothesis.     

Spatial attention is necessary for object-based attention: Evidence from temporal-order judgments

Attentional selection is a dynamic process that relies on multiple types of representations. That object representations contribute to attentional selection has been known for decades; however, most evidence for this contribution has been gleaned from studies that have relied on various forms of spatial cueing (some endogenous and some exogenous). It has thus remained unclear whether object-based attentional selection is a direct result of spatial cuing, or whether it still emerges without any spatial marker. Here we used a novel method—the temporal-order judgment (TOJ)—to examine whether object-based guidance emerges in the absence of spatial cuing. Participants were presented with two rectangles oriented either horizontally or vertically. Following a 150-ms preview time, two target stimuli were presented on the same or on different objects, and participants were asked to report which of the two stimuli had appeared first. The targets consisted of stimuli that formed a percept of a “hole” or a “hill.” First, we demonstrated that the “hill” target was indeed processed faster, as evidenced by a positive perceived simultaneity (PSS) measure. We then demonstrated that if two targets appeared with equal probabilities on the same and on different objects, the PSS values, although positive, were not modulated by the objects. In a subsequent set of experiments, we showed that objects can modulate attentional allocation—however, only when they are biased by a spatial (endogenous) cue. In other words, in the absence of a spatial cue or bias, object representations do not guide attentional selection. In addition to providing new constraints for theories of object-based attentional guidance, these experiments introduce a novel paradigm for measuring object-based attentional effects.     

Division of attention: Age differences on a visually presented memory task

Young and old adults were compared in their efficiency of remembering concurrently presented series of letters and digits in three separate experiments. Instructions and payoffs to vary attentional emphasis across the two types of material in different conditions allowed the examination of attention-operating characteristics in the two age groups. Strategy-independent measures derived from these attention-operating characteristics revealed that older adults exhibited greater performance deficits than young adults when dividing their attention between the two tasks, even though dual-task difficulty was individually adjusted for each subject. It was concluded that either the total amount of attention available for distribution or the efficiency of its allocation decreased with age even though the ability to vary one’s attention between concurrent tasks in response to instructions and payoffs remained intact.     

Evidence for split foci of attention in a priming paradigm

Most models of visuospatial attention include the notion that attention is dedicated to a single location in space. However, several researchers have found evidence that under appropriate circumstances, attention may be allocated to noncontiguous locations (e.g., Awh & Pashler, 2000; Bichot, Cave, & Pashler, 1999; Kramer & Hahn, 1995). In the present experiments, the spatial distribution of attention was assessed by a novel method, perceptual latency priming: the latency benefit of an attended visual stimulus, as compared with a nonattended stimulus. Experiment 1 assessed whether observers are able to attend to two nonadjacent regions or a region of variable size. Experiment 2 tested whether, when two distant locations are attended to, the region between them is necessarily also in the focus of attention. Two further experiments controlled for objections against the method used and replicated the main results of the first two experiments. The experiments showed a robust attentional priming effect at two noncontiguous locations of the visual field, simultaneous with little or no priming of the intervening location.     

Divided attention: Evidence for coactivation with redundant signals

Many models of divided attention assume that signals presented on different channels produce separate activations, any one of which can initiate a response. According to these models, detection responses are especially fast when signals are presented on two channels at the same time because the system can detect a signal in either of two ways. Such models predict a testable relation among reaction time distributions for conditions in which a single signal is presented as compared with a condition in which two signals are presented, and this prediction is tested in two tasks. A bimodal detection task required a simple speeded response to either a visual or an auditory signal. A letter search task required a choice response depending on whether or not a two-letter display included the signal letter “A.” Data from both tasks are inconsistent with the prediction. When two signals are presented, responses are faster than separate-activation models can explain. The results favor “coactivation” models, in which signals presented on different channels contribute to a common pool of activation that initiates a response.     

Assessing attention control in goal pursuit: a component of dispositional self-regulation

We examined the psychometric properties of the Self-Regulation Scale (SRS; Schwarzer, Diehl, & Schmitz, 1999), a measure of attention control in goal pursuit, in 2 independent studies. Study 1 included young adults (N = 443), whereas Study 2 included young, middle-aged, and older adults (N = 330). In both studies, the SRS showed good internal consistency. In Study 1, the SRS also showed satisfactory test-retest reliability over a 6-week period. We found support for the criterion validity of the SRS in terms of positive correlations with measures of general and domain-specific self-efficacy, proactive coping, and positive affect and in terms of negative correlations with depressive symptoms and negative affect. Hierarchical regression analyses showed that attention control accounted for unique portions of variance in relevant outcome variables above and beyond measures of self-efficacy and proactive coping.     

Search for multiple targets: Evidence for memory-based control of attention

There are two opposing models with regard to the function of memory in visual search: a memorydriven model and a memory-free model. Recently, Horowitz and Wolfe (2001) investigated a multipletarget search task. Participants were required to decide whether or not there were at leastn targets present. They demonstrated that the reaction time ×n function has a positive and accelerated curve. They argued that the memory-free model predicts this curve, whereas the memory-driven model predicts a linear function. In this study, I varied the total set sizes of a multiple-target search task and fitted the models separately for eachn condition. The model fit indicated that the memory-driven model is more appropriate than the memory-free model in eachn condition. These results suggest that an amnesic process does not cause the positive accelerated curve of the reaction time ×n function but that it is the result of the time needed to examine each additionaln item.     

On varying the span of visual attention: Evidence for two modes of spatial attention

Three experiments investigated whether subjects could selectively attend to a target item presented in close spatial proximity to a distractor element. Typically, the display consisted of two curved lines, one a target and the other a distractor. The task was to judge the direction of curvature of the target. When subjects attended to a target away from fixation, performance was affected by the presence of a distractor within an area of 1° around the target. In contrast, the distractor did not influence target processing when subjects fixated on the target location. Two modes of visual attention are proposed. When a target is located away from fixation, a “wide” attentional span is employed. With the present stimuli, this led to the detailed processing of items within 1° of the attended position. However, when targets are at fixation a “narrow” span can be adopted, with the result that there is differential processing of attended items even within the formerly critical area.     

Personally-significant information affects performance only within the focus of attention: a direct manipulation of attention

It has been suggested that personally significant (PS) information interferes with performance only when presented within the focus of attention. However, this claim was never tested by a systematic manipulation of attention, but only by using correlative measures of its locus. We addressed this issue in two experiments, utilizing a cued visual search paradigm that allowed us to directly manipulate attention and to measure behavioral and physiological responses. One of the stimuli in the search display had a higher luminance value (i.e., was cued), and, orthogonally, one of the stimuli could be a PS or neutral name. When the cue did not predict target location, PS distractors mildly interfered with task performance, regardless of the cue's location. However, when the cue predicted target location, responses were facilitated for cued targets, indicating that attention was shifted to the cue. Importantly, PS distractors interfered with task performance and elicited enhanced orienting responses only when they were cued. This implies that PS information affects performance only when presented within but not outside the focus of attention.     

Age changes in assembly performance: a component analysis

100 children from Kindergarten to Grade 9 (i.e., 5 to 15 yr.) performed a one-handed manual dexterity assembly task. The videotaped performances were analyzed for the components, Grasping, Transporting, Positioning, Reaching, and Pauses. All five components contributed significantly to the improvements in the lower grades. The Grasping component deteriorated significantly in the older children, but Reaching and Positioning continued to improve up to Grade 9. There were no sex differences.     

Feature-based control of attention: Evidence for two forms of dimension weighting

In three experiments, I examined whether prior knowledge of a target feature dimension is useful for guiding spatial attention to the target in a variety of tasks: visual search (Experiments 1A and 1B), texture segregation (Experiment 2), and visual enumeration (Experiment 3). Experiment 1A used a simple search task and found that reaction times for blocks in which a target was defined within a single feature dimension were shorter than those for blocks in which a target was defined across dimensions (within-dimension facilitation; WDF). Intertrial facilitation (ITF; Müller, Heller, & Ziegler, 1995), a dimension-based priming effect from one trial to the immediately following one, was also observed. Both WDF and ITF disappeared when the same stimuli were used under a compound search task (Experiment 1B), in which participants responded to an attribute of the target in a feature dimension different from its defining dimensions. Experiments 2 and 3 showed that WDF and ITF are not necessarily contingent upon each other: In a texture discrimination task, only WDF was found; in an enumeration task for six or seven targets, only ITF was found. These results show that the two forms of dimension weighting, WDF and ITF, are mediated by different mechanisms. WDF was eliminated when focal attention to targets was required, suggesting that feature-based modulation is limited as a source for controlling spatial attention (Kumada, 1999). ITF was correlated with type of response, suggesting dimension-specific response mechanisms (Cohen & Shoup, 1997).     

Switching attention within and between categories: Evidence for intracategory inhibition

In a variation of the Posner and Snyder (1975b) paradigm, subjects made speeded “same” or “different” responses to pairs of digits or letters on the basis of name identity (Experiment 1) or physical identity (Experiment 2). Each target pair was preceded by an informative (letter or digit) or noninformative (plus-sign) warning signal. The letter or digit represented by an informative warning signal had a high probability of appearing in the subsequent target pair (expected condition). On trials in which the expected stimulus did not appear in the target pair, the target pair belonged with equal probability to either the same category (either letters or digits) as the expected stimulus or to the opposite category (unexpected-similar and unexpected-opposite conditions, respectively). The pattern of “benefits” and “costs” of attentional expectancy found by Posner and Snyder for “same” responses was replicated: Subjects were faster and more accurate in the expected condition than in the neutral (uninformative warning signal) condition, but slower and less accurate in the unexpected conditions. Present theoretical interest concerns “same” response times and accuracy for the two unexpected conditions. Under instructions emphasizing accuracy as well as speed (Experiments 1 and 2), performance was worse in the unexpected-similar condition than in the unexpected-opposite condition. Only when instructions deemphasized accuracy (Experiment 2) was performance better in the unexpected-similar condition than in the unexpected-opposite condition. The fact that subjects may have more difficulty switching attention within a category than between categories (at least when instructions emphasize accuracy as well as speed) contrasts sharply with current theoretical emphasis on intracategorical facilitation effects in the priming paradigm. The results are interpreted within the framework of a model of attention (Keele & Neill, 1978) in which the activation of associates to the focus of attention is actively and optionally suppressed so as to reduce present or potential interference with the focal information processing.     

自我信息识别优势——来自注意定向网络的证据

研究采用注意网络测验任务(attention network test, ANT), 分别检验自我相关信息在注意的警觉、定向和执行控制网络上的加工效率差异, 以揭示自我信息识别优势的注意机制。实验1考察了面孔类型(自我面孔或他人面孔)在3种注意网络下的加工效率差异; 实验2采用自我联结学习范式对实验1进行验证; 实验3将颜色类型(红色或绿色)作为目标刺激, 面孔类型作为背景, 以考察任务无关自我信息是否对注意网络加工效率有影响。研究结果发现, 当自我信息为目标时, 个体在注意定向网络上存在加工效率优势, 而警觉和执行控制网络上没有加工效率差异。当自我相关信息与任务无关时, 在注意的警觉、定向和执行控制网络中均未表现出加工效率优势。说明了自我信息的注意优势发生在注意定向网络上, 且受任务优先性影响。     

自我面孔对空间注意的调控：来自Posner空间线索范式的证据

利用Posner的空间线索范式,三个实验意在探寻自我面孔作为特殊的刺激对空间注意的调控作用。在实验一中,自我或者熟悉的面孔作为内源性线索出现在视野中央,通过朝左或者朝右来提示目标出现的位置。在实验二（小图）和实验三（大图）中,自我或熟悉的面孔与目标同时呈现,作为与任务无关的刺激出现在视野的左侧或右侧。实验一的结果发现,与熟悉的面孔相比较,自我面孔产生了更大的提示效应。这意味着当自我面孔与任务相关时,对提示位置易化优于熟悉的面孔。与之相反的是,在实验二和实验三中,自我面孔和熟悉的面孔同样捕获目标位置的空间注意。然而,研究并没有发现自我面孔与熟悉面孔在捕获注意上的差异。这一结果也许暗示着在注意捕获的过程中,面孔效应足够大而掩盖了自我效应的出现。这些发现表明自我面孔之所以是具有特殊性的刺激不仅受感知过程的影响,还依赖于与任务的关系。     

A repetition-suppression account of between-trial effects in a modified Stroop paradigm

Theories that postulate cognitive inhibition are very common in psychology and cognitive neuroscience [e.g., Hasher, L., Lustig, C., & Zacks, R. T. (2007). Inhibitory mechanisms and the control of attention. In A. Conway, C. Jarrold, M. Kane, A. Miyake, A. Towse, & J. Towse (Eds.), Variation in working memory (pp. 227-249). New York, NY: Oxford, University Press], although they have recently been severely criticized [e.g., MacLeod, C. M., Dodd, M. D., Sheard, E. D., Wilson, D. E., & Bibi, U. (2003). In opposition to inhibition. In H. Ross (Ed.), The psychology of learning and motivation (Vol. 43, pp. 163-214). Elsevier Science]. This paper poses and attempts to answer the question whether a research program with cognitive inhibition as its main theoretical assumption is still worth pursuing. We present a set of empirical data from a modified Stroop paradigm that replicates previously reported findings. These findings refer to between-trial effects previously described in the literature on Stroop, negative priming, and inhibition-of-return. Existing theoretical accounts fail to explain all these effects in an integrated way. A repetition-suppression mechanism is proposed in order to account for these data. This mechanism is instantiated as a computational cognitive model. The theoretical implications of this model are discussed.     

Evidence for intact memory-guided attention in school-aged children

Visual scenes contain many statistical regularities such as the likely identity and location of objects that are present; with experience, such regularities can be encoded and can ultimately facilitate the deployment of spatial attention to important locations. Memory-guided attention has been extensively examined in adults with the 'contextual cueing' paradigm and has been linked to specific neural substrates – a medial temporal lobe (MTL)-frontoparietal network. However, it currently remains unknown when this ability comes 'online' during development. Thus, we examined the performance of school-aged children on an age-appropriate version of the contextual cueing paradigm. Children searched for a target fish among distractor fish in new displays and in 'old' displays on a touchscreen computer. Old displays repeated across blocks of trials and thus provided an opportunity for prior experience with the invariant configuration of the stimuli to guide attentional deployment. We found that over time children searched old displays significantly faster than new displays, thus revealing intact memory-guided attention and presumed function of an MTL-frontoparietal network in 5- to 9-year-olds. More generally, our findings suggest that children are remarkably sensitive to the inherent structure of their visual environment and this enables attentional deployment to become more efficient with experience.     

Divided attention modulates semantic activation: Evidence from a nonletter-level prime task

Research has recently shown that semantic activation is modulated in proportion to the amount of attention required for letter-level processing of the prime (the attention modulation hypothesis; Smith, Bentin, & Spalek, 2001). In this study, we examined this hypothesis with an auditory divided-attention task. Participants were asked to decide whether the pitch of a probe tone presented with the prime word was higher or lower than the basic tone presented with the fixation cross. Their target task was lexical decision to the target word. Experiment 1 showed that semantic priming was modulated by the amount of attentional resources. Moreover, in Experiment 2, this modulation was also found in a situation that eliminated the possibility of participants' response strategies. Yet, Experiment 3 showed repetition priming to be unaffected. These results support an amended attention modulation hypothesis in which modulation is not limited to letter-level processing.