多个非线索化位置易化的一项实验研究

现在采用返回抑制范式所进行的空间非信息线索作用的研究,大多以非线索化位置反应时为参照,发现线索化位置的反应先易化后抑制。后者即返回抑制。本研究采用在返回抑制范式上增设中性线索化条件的方法,发现当靶子可以出现的位置为四个时,相对于中性线索化条件,非线索化位置反应快。这种非线索化位置的易化作用是独立存在的,它能使生物体尽快地付出现在多个非线索化位置的靶子有出反应。     

重复线索化和靶子注意定向对返回抑制的影响

在返回抑制范式下 ,利用线索—靶子模式进行了两个实验 ,以大学生为被试 ,以重复线索化次数来操纵线索化阶段的注意 ,以靶子的注意定向来操纵靶子加工阶段的注意 ,探讨注意对返回抑制的影响。实验一采用连续线索化方式 ,发现当靶子为自主性注意定向时 ,线索化次数对返回抑制有显著影响 ,线索化 3次时返回抑制值大于线索化 1次和 2次 ;当靶子为反射性注意定向时 ,线索化次数对返回抑制无影响。实验二采用交叉线索化方式 ,发现线索化次数对返回抑制的影响正好与实验一相反。两个实验一致表明 ,无论是线索化阶段的注意 ,还是靶子加工阶段的注意 ,均对返回抑制有显著影响 ;并且 ,在对返回抑制的影响上 ,二者存在显著交互作用。从而支持注意影响返回抑制的观点。该结果对返回抑制的机制研究有一定意义。     

返回抑制研究的新进展

Ｐｏｓｎｅｒ和Ｃｏｈｅｎ( 1984 )发现对空间某一位置进行线索化 ,在线索开始呈现到靶子开始呈现的时间间隔 (ＳＯＡ)约等于或大于 30 0毫秒时 ,被试对线索化位置上靶子的反应时长于非线索化位置 ,出现抑制效应。他们称之为返回抑制 (ｉｎｈｉｂｉｔｉｏｎｏｆｒｅｔｕｒｎ ,简称ＩＯＲ)。返回抑制的实验范式是在外周位置线索化后 ,间隔一段时间 (在此间隔时间内可插入也可不插入中央注视点线索化 ) ,然后靶子呈现在线索化位置或者非线索化位置上。早期返回抑制的研究涉及其特性和机制等多方面的问题 ,近期则倾向于将返回抑制和其它实验范…     

外框数目、线索数目和线索类型对返回抑制的影响

采用被试内重复测量设计和经典的线索—靶子实验范式,考查了外框数目（4和8）、线索数目（1和3）、不同线索类型（on-off线索（即线索出现后消失）、onset线索（即线索持续呈现））对返回抑制的影响,发现靶子潜在位置数目越多反应时越长,返回抑制量越小;线索数目越少反应时越长,返回抑制量越大;onset线索反应时长于on-off线索,onset线索产生的返回抑制量大于on-off线索。这表明空间工作记忆负载和记忆痕迹会影响返回抑制。     

靶子的潜在位置数对辨别任务中返回抑制的影响

摘要在严格控制的条件下,以大学生为被试．采用线索一靶子模式的返回抑制范式．考察了靶子在注视点周边可能出现的位置数与辨别任务中返回抑制的关系。实验结果表明．在辨别任务中靶子的潜在位置数对返回抑制量有影响,随着位置数的增加,返回抑制量减小。该结论为返回抑制的注意性观点提供了新的证据。     

返回抑制和抑制标签在长时训练下的分离

返回抑制(Inhibition of return, IOR)是指当线索-靶子的时隔大于约300 ms时, 被试对呈现在线索化位置的靶子相较对出现在非线索化位置的靶子而言反应更慢的现象。新近抑制标签 (Inhibitory tagging, IT) 理论指出, 除返回抑制外, 一个由前额叶执行控制系统负责的抑制标签机制也作用于先前线索化位置, 起着暂时中断刺激-反应链接的作用。然而, 迄今为止, 该理论的关键假设-“抑制标签一定程度上独立于返回抑制发挥作用”还未有来自常规被试研究的支持。结合线索-靶子和Stroop范式, 采用8(训练天数)×2(线索-靶子关系)×3(色字一致性)的三因素被试内实验设计, 通过连续8天的长时训练对常规被试的返回抑制和抑制标签功能在学习可塑性上的差别进行考察。结果发现, 返回抑制随着练习的增加呈现出了显著降低的趋势, 而抑制标签并未随着练习的变化而变化。研究结果表明返回抑制和抑制标签在一定程度上可以相互分离, 为抑制标签理论的关键假设提供了重要的来自常规被试的证据。     

不同线索下特质焦虑个体的返回抑制

焦虑与注意偏向的研究是近年来情绪与认知领域的热点。为探讨特质焦虑个体的注意偏向特点及其返回抑制能力是否受不同线索的调节, 采用特质焦虑量表筛选高特质焦虑大学生29名, 低特质焦虑大学生28名完成线索-靶子任务。要求被试在提示线索消失后, 对位置进行快而准地辨别反应, 分别探索中性和情绪性提示线索下被试的返回抑制。结果发现：(1)在中性线索条件下, 高焦虑个体平均反应时慢于低焦虑个体。(2) 在情绪线索条件下, 高焦虑个体在负性线索下的反应时小于在正性线索下的反应时; 高、低焦虑个体在各种SOA条件下均出现了返回抑制, 但各组返回抑制量受到情绪线索的调节：在正性情绪线索条件下, 两组返回抑制量没有显著差异; 在负性情绪线索下, 高焦虑个体返回抑制量显著小于低焦虑个体。这表明, (1)焦虑个体的注意偏向受到刺激信息的影响：只对负性情绪线索出现注意警觉; (2)只有在涉及负性情绪信息时高、低焦虑个体返回抑制能力才有差异, 高焦虑个体存在对负性情绪线索的抑制困难。     

返回抑制对工作记忆储存和目标维持的影响

将线索一靶子范式和N—Back变式结合,以工作记忆的记忆错误和侵入错误数为指标,探讨了返回抑制与工作记忆的储存和加工之间的关系,并对返回抑制的机制进行了深入探讨。结果表明,当记忆项目出现在线索化位置时,两种错误数均显著高于出现于非线索化位置的情况,但侵入错误的抑制效应只出现于长SOA条件。这揭示了返回抑制既影响工作记忆的储存又影响对任务目标的维持,也为返回抑制的注意说提供了新证据。     

阈上和阈下不同情绪线索对返回抑制的影响

为检验返回抑制是否受线索生物学意义的调节, 分别在实验一和实验二中以阈上和阈下不同情绪效价(高兴、生气和中性)的面孔为外源性线索, 变化同时提示位置的多寡, 要求被试对靶子尽可能快而准地作探测反应。实验一发现, 三种线索情况下均出现返回抑制且效应量无显著差异; 实验二发现, 线索为中性面孔时出现返回抑制, 线索为高兴和生气面孔时未出现返回抑制。说明返回抑制受线索生物学意义的调节。阈下线索的生物学意义(情绪效价)能得到自动加工, 从而影响空间注意的转移和返回抑制机制的功用; 阈上线索的情绪效价被清晰感知时, 自上而下的注意控制机制使线索的生物学意义被忽略, 从而阻碍情绪效价功能的发挥。     

线索有效性对儿童返回抑制的影响

采用通常的线索—靶子实验,来考察不同的线索有效性对儿童返回抑制的影响。所用的外源性线索分高有效性、低有效性和非信息性三类。儿童被试在实验中的任务为觉察圆形光点后即按键反应,记录反应时。结果表明,7岁、9岁和11岁儿童在高有效性和非信息性线索条件下均出现返回抑制;但7岁和9岁儿童在低有效性线索条件未出现返回抑制,而11岁儿童则出现。这些儿童的实验结果有别于成人。结果提示,7岁、9岁和11岁儿童的返回抑制是在外源性线索的作用下自动出现的,具有反射性质;但7岁和9岁儿童的返回抑制仍受线索有效性的制约,而11岁儿童返回抑制的发展已不受线索有效性的影响。     

Effects of response priming and inhibition on movement planning and execution

The authors used a precueing method to examine the effects of response priming and inhibition on goal-directed action. Participants (N = 18) completed aiming movements to 1 of 2 locations following predictive (80% cued), nonpredictive (50% cued), and antipredictive (20% cued) precues at 1 of the 2 possible target locations. Consistent with previous research, participants responded more quickly to targets at cued locations than to targets at uncued locations in the 80% condition, and more quickly to targets presented at the uncued than to those presented at cued locations in the 50% and 20% conditions. As predicted by models of action-centered selective attention, movement trajectories deviated away from the cued location in the 50% condition. Movement trajectories were also altered in the 80% and the 20% conditions. Movements directed to the uncued location deviated away from the cued location in the 80% condition, whereas movements directed to the cued location deviated away from the uncued location in the 20% condition. The authors explain the latter trajectory results as a strategy of overcompensation.     

The relationship between covert and overt attention in endogenous cuing

In a standard Posner paradigm, participants were endogenously cued to attend to a peripheral location in visual space without making eye movements. They responded faster to target letters presented at cued than at uncued locations. On some trials, instead of a manual response, they had to move their eyes to a location in space. Results showed that the eyes deviated away from the validly cued location; when the cue was invalid and attention had to be allocated to the uncued location, eye movements also deviated away, but now from the uncued location. The extent to which the eyes deviated from cued and uncued locations was related to the dynamics of attention allocation. We hypothesized that this deviation was due to the successful inhibition of the attended location. The results imply that the oculomotor system is not only involved during the endogenous direction of covert attention to a cued location, but also when covert attention is directed to an uncued location. It appears that the oculomotor system is activated wherever spatial attention is allocated. The strength of saccade deviation might turn out to be an important measure for the amount of attention allocated to any particular location over time.     

Stimulus discrimination following covert attentional orienting to an exogenous cue.

Five experiments explored exogenous covert visual-attentional orienting following a brief peripheral cue. On each trial an attentional cue was followed by a stimulus in an empty field at 1 of 8 locations on an imaginary circle centered on the fixation point. The cued area size and the cue-target spatial relation were manipulated. Accuracy and response time were affected by the exogenous cue validity. Attention was allocated to a specific location in a visual quadrant: A target at an uncued location in a quadrant was not facilitated as much as target at the cued location, and a target in a different quadrant was inhibited in relation to a neutral condition. Cuing 2 locations in a quadrant was not as facilitative for targets at the cued locations or as inhibitive for targets at other locations compared with cuing a single location in a quadrant. Results are discussed in the context of several extent models of covert visual-spatial attention.     

Movement versus focusing of visual attention

In two experiments, we investigated the idea that attention moves through visual space in an analog fashion. The spatial distribution of attention was determined by presenting a spatially informative cue and comparing reaction times to targets at cued and uncued locations as a function of the interval from cue onset to target onset (SOA). Facilitation and inhibition were measured by reference to a neutral condition in which the cue provided no spatial information. In the first experiment, we used a central cue (an arrow), and in the second experiment, we used a peripheral cue (a 50-msec flash). With central cue, the facilitatory effects of the cuing were initially equal for all locations on the indicated side of the display, and then decreased for all locations except the one that had been specifically cued. These results are interpreted as being more consistent with "focusing" of an initially broad "beam" of attention than with "movement" of a narrow beam from fixation to the cued location. With peripheral cues, strong facilitation specific to the cued location was manifest as early as 50 msec after cue onset, but this effect decreased with increasing SOA. Inhibition for uncued locations increased with increasing SOA at a rate that generally reflected their distance from the cued location. Taken together, these results reveal important differences between peripheral and central cues in the generation of attentional selectivity, not just in the time-course of events, but also in the nature of the processes involved.     

The effect of previous trial type on inhibition of return

Inhibition of return (IOR) refers to the finding that targets appearing at previously cued locations are more slowly responded to than targets appearing at previously uncued locations when a relatively long temporal interval occurs between the cue and target. This experiment was conducted to determine whether the magnitude of IOR is influenced by the type of preceding trial (cued or uncued) and/or the location of the cue/target on the previous trial. Although no effect of cue/target location is observed, there was a marked effect of previous trial type, as IOR was greater following an uncued trial relative to a cued trial. This effect was attributable to differences in the response time as a function of previous trial type: specifically, participants were faster to respond to cued and uncued trials when the previous trial type was identical.     

Visuospatial attention in schizophrenia: deficits in broad monitoring

Although selective attention is thought to be impaired in people with schizophrenia (PSZ), prior research has found no deficit in the ability to select one location and withdraw attention from another. PSZ and healthy control subjects (HCS) performed a stimulus detection task in which one, two, or all four peripheral target locations were cued. When one or two locations were cued, both PSZ and HCS responded faster when the target appeared at a cued than uncued location. However, increases in the number of validly cued locations had much more deleterious effects on performance for PSZ than HCS, especially for targets of low contrast whose detection was more dependent on attention. PSZ also responded more slowly in trials with four cued locations relative to trials with one or two invalidly cued locations. Thus, visuospatial attention deficits in schizophrenia arise when broad monitoring is required rather than when attention must be focused narrowly.     

Covert visual orienting: Hemifield-activation can be mimicked by zoom lens and midlocation placement strategies

How is attention distributed over visual space when an observer expects a target to occur at one of several possible locations? Two experiments sought to understand the source of the conflict between studies leading to the notions of hemifield activation (Hughes and Zimba 1985) and attentional gradients (Downing and Pinker 1985; Shulman et al. 1985, 1986). Subjects were cued to attend one of the 4 corners of an imaginary square centered at fixation, allowing comparison of uncued locations in the cued and uncued hemifields. In one experiment marking of the 4 locations was varied to determine if providing a ‘target’ for attention is necessary to obtain within-hemifield gradients. RT was faster at the cued location than at the three uncued locations which had equivalent latencies, a pattern that was unaffected by marking of the potential target locations. This result, which is consistent with the notion of a gradient around the attended location is a strong disconfirmation of the hemifield activation hypothesis. The second experiment demonstrated that an unusual procedure for presenting the probe stimuli in Hughes and Zimba (1985) is at least partially responsible for their evidence for uniform hemifield activation. It is proposed that visual attention is directed to visuo-spatial channels with fixed structural properties, and that when attention to two locations is desired, the subject may attend a spatial channel located between them.     

Configural and contextual prioritization in object-based attention

When attention is directed to a location within an object, other locations within that object also enjoy an attentional advantage. Recently we demonstrated that this object-based advantage is mediated by increased attentional priority assigned to locations within an already attended object and not to early sensory enhancement due to the "spread" of attention within the attended object (Shomstein & Yantis, 2002). At least two factors might contribute to the assignment of attentional priority, one related to the configuration of objects in a scene and the other related to the probability of target appearance in each location imposed by task contingencies. We investigated the relative contribution of these factors by cuing one end of one of a pair of rectangles; a subsequent target appeared most often in the cued location. We manipulated attentional priority setting by varying (1) the probability that a target would appear in each of two uncued locations and (2) the cue to target stimulus onset asynchrony (SOA). On invalidly cued trials, the target appeared in the high-probability location (defined by an absolute spatial location, e.g., upper right) 83% of the time and in the low-probability location (e.g., lower left) 17% of the time. In both conditions, uncued targets appeared in the cued object half the time and in the uncued object half the time. At short SOAs, the same-object and probability effects were approximately additive. However, at longer SOAs, the same-object effects disappeared, and reaction times depended exclusively on location probability. These results suggest that observers adopt an implicit configural scanning strategy (in which unattended locations within an attended object have high priority) or an implicit contextual scanning strategy (in which objectively high-probability locations have high priority) depending on task contingencies and the amount of time that is available to deploy attention.     

The effect of shape and location on temporal masking of spatial vibrotactile patterns

Target patterns presented to uncued locations on a single fingerpad were followed by either same-shape (SS) maskers or different-shape (DS) maskers presented to either the same location (SLoc) or a different location (DLoc). DS maskers interfered with identification more when they were at SLoc than when they were at Dloc, but the reverse was true for SS maskers; they interfered more at DLoc than at SLoc. When targets were presented to cued locations, performance in the absence of maskers improved, but the pattern of interference from maskers resembled that for uncued presentation. The proportion of masker responses on incorrect trials revealed that both temporal masking and response competition may be involved in the effects of location on pattern identification.     

Object-based control of attention is sensitive to recent experience

How is attention guided by past experience? In visual search, numerous studies have shown that recent trials influence responses to the current trial. Repeating features such as color, shape, or location of a target facilitates performance. Here we examine whether recent experience also modulates a more abstract dimension of attentional control, object-based and location-based control. Participants performed a cued target discrimination task with stimuli presented on 2 rectangles. Response times to targets appearing in an uncued location on a cued rectangle were faster than to targets on the uncued rectangle, demonstrating an object-based attentional benefit. We investigated the object-based benefit on the current trial contingent on the cue-target relationship on the previous trial. The object-based benefit was significant only when the cued object contained the target on the previous trial, not when the uncued object contained the target. This effect of recent experience was not due to either the repetition of spatial cue-target location or the repetition of the response, but to adaptation to contingencies in the environment. Our results suggest a unifying view of attentional control that spans the concrete dimensions of control (e.g., determining the relative importance of red vs. blue) to the abstract (determining the relative importance of objects vs. locations in space). Attention closely tracks the short time scale structure of the environment and automatically adapts to optimize performance to this structure.