Dividing attention between the color and the shape of objects

In many dual-task experiments, the priority observers give to each task is experimentally varied. Most experiments using this methodology have studied the effect of dividing attention between spatially distinct objects. We examined performance when attention had to be divided between stimulus attributes other than spatial location. In the first experiment, observers identified the color and the shape of a single letter. Accuracy was the same for single- and dual-task conditions, and a trialby-trial analysis revealed a strong positive correlation in the correct identification of the color and the shape. In the second experiment, color and shape judgments were separated in space, with opposite results: Dual-task performance was worse than single-task performance, and the trial-by-trial analysis indicated a strong negative correlation between tasks. The results indicated that often only one dimension was processed within a trial. The results support object and space models of attention.     

A demonstration of direct access to colored stimuli following cueing by color

To test whether cueing by color can affect orienting without first computing the location of the cued color, the impact of reorienting on the validity effect was examined. In Experiment 1 subjects were asked to detect a black dot target presented at random on either of two colored forms. The forms started being presented 750 ms before the onset of a central cue (either an arrow or a colored square). In some proportion of the trials the colors switched locations 150 ms after cue onset, simultaneously with target onset. The color switch was not found to retard responses following a color cue more than following a location cue. Furthermore, it did not reduce the validity effect of the color cue: Though the validity effect of the location cue was quite larger than the validity effect of the color cue, both effects were additive with the presence/absence of a color switch. In Experiment 2, subjects were rather asked to detect a change in shape of one of the colored forms. In this case, color switch was found to affect performance even less following a color cue. The fact that across experiments, color switch did not retard neither responding nor orienting selectively in the color cue condition, indicates that when attention is set to a certain color, reorienting to a new object following color switch does not require re-computing the address of the cued color. That finding is argued to embarrass a strong space-based view of visual attention.     

Attentional resource demands of visual word recognition in naming and lexical decisions.

Attentional demands of lexical access were assessed with dual-task methodology. Subjects performed an auditory probe task alone (single-task) or combined (dual-task) with either a lexical decision or a naming task. In Experiment 1, probe performance showed a decrement from single- to dual-task conditions during recognition of words in both lexical decision and naming tasks. In addition, decrements in probe performance were larger during processing of low-frequency compared with high-frequency words in both of the word recognition tasks. Experiment 2 showed that the time course of frequency-sensitive demands was similar across lexical decision and naming tasks and that attention is required early in the word recognition sequence. The results support the assumption that lexical access is both frequency sensitive and attention demanding.     

Automaticity and the detection of speech

The development of automatic perceptual responses to speech stimuli was examined. In the first experiment, phoneme-monitoring performance for speech syllables was examined under conditions in which stimulus-to-response mapping and memory load were manipulated. The results indicated that automaticity develops under consistent-mapping conditions. In the second experiment, a dual-task procedure was combined with mapping and selective attention manipulations in order to examine the development of automaticity across single- and multiple-channel conditions. The results indicated that performance under consistently mapped training conditions was interfered with by dividing attention across multiple channels of input. It is concluded that there may be differences in the way that automaticity develops across visual and auditory modalities and that these differences need to be examined more closely.     

Attention alters the appearance of motion coherence

Selective attention enhances visual information processing, as measured by behavioral performance and neural activity. However, little is known about its effects on subjective experience. Here, we investigated the effect of transient (exogenous) attention on the appearance of visual motion, using a psychophysical procedure that directly measures appearance and controls for response bias. Observers viewed pairs of moving dot patterns and reported the motion direction of the more coherent pattern. Directing attention (via a peripheral precue) to a stimulus location increased its perceived coherence level and improved performance on a direction discrimination task. In a control experiment, we ruled out response bias by lengthening the time interval between the cue and the stimuli, so that the effect of transient attention could no longer be exerted. Our results are consistent with those of neurophysiological studies showing that attention modulates motion processing and provide evidence of a subjective perceptual correlate of attention, with a concomitant effect on performance.     

Color-based inhibition of return

The inhibition of return of visual attention based on stimulus color was examined in three experiments. In the first experiment, a discrete trial paradigm showed that subjects were slower to detect a color patch if the color matched that of a patch presented earlier in the same location. Experiment 2 showed that the inhibition only occurs if a neutral, nontarget distractor color is presented between presentation of the initial color cue and the subsequent target patch—explaining the previous failures to detect the phenomenon. Experiment 3 extended the results to a different combination of colors. Taken together, the results have important implications for the processing of stimulus attributes such as spatial location and color, and for the conditions necessary for producing inhibition of return.     

颜色和形状工作记忆对非空间返回抑制效应的影响

为进一步考察非空间返回抑制效应是否受工作记忆内容的影响,分别采用颜色和形状工作记忆内容,通过两个实验考察了工作记忆对非空间返回抑制效应的影响。实验结果表明,在颜色和形状工作记忆条件下,均产生了颜色或形状返回抑制效应,并且颜色或形状返回抑制效应量之间均无显著差异,颜色和形状工作记忆内容只增加了判断靶刺激的反应时。研究结论对进一步认识工作记忆内容与非空间返回抑制效应之间的关系有重要参考价值。     

动态情景中颜色特征和身份特征在返回抑制中的作用

在动态的“线索-靶子”范式中引入隧道刺激, 以靶子与线索的非空间特征相同时的反应延迟测量返回抑制效应。实验1利用单向隧道创设客体的空间位置信息明确且可靠的条件, 考察客体的颜色特征在返回抑制中的作用。实验2利用双向隧道创设客体的空间位置信息不明确的条件, 考察客体的颜色特征在返回抑制中的独立作用。实验3、4分别采用与实验1、2类似的方法, 在动态任务情景中考察客体的身份特征在返回抑制中的作用。结果显示, 线索呈现与靶子呈现的时间间隔较长时, 4个实验中均存在显著的返回抑制效应。这表明, 动态情景中, 客体的空间位置信息明确且可靠时, 颜色特征和身份特征在返回抑制中都发挥着重要作用; 客体的空间位置信息不明确时, 颜色特征和身份特征在返回抑制中也都具有相对独立的作用。     

Attentional capture by motion onsets is spatially imprecise

Using straight translatory motion of a visual peripheral cue in the frontoparallel plane, and probing target discrimination at different positions along the cue's motion trajectory, we found that target orientation discrimination was slower for targets presented at or near the position of motion onset (4.2° off centre), relative to the onset of a static cue (Experiment 1), and relative to targets presented further along the motion trajectory (Experiments 1 and 2). Target discrimination was equally fast and accurate in the moving cue conditions relative to static cue conditions at positions further along the cue's motion trajectory (Experiment 1). Moreover, target orientation discrimination was not slowed at the same position, once this position was no longer the motion onset position (Experiment 3), and performance in a target colour-discrimination task was not slowed even at motion onset (Experiment 4). Finally, we found that the onset location of the motion cue was perceived as being shifted in the direction of the cue's motion (Experiment 5). These results indicate that attention cannot be as quickly or precisely shifted to the onset of a motion stimulus as to other positions on a stimulus’ motion trajectory.     

Cueing attention by relative motion in the periphery of the visual field

Sudden changes of visual stimulation attract attention. The observer's body motion generates retinal-flow field patterns containing information about his/her own speed and trajectory and relative motion of other objects. We investigated the effectiveness of relative motion as an attentional cue and compared it with conventional cueing by appearance of a frame in the far periphery of the visual field. In a group of ten subjects, contrast thresholds for the perception of static Gabor grating orientation [four alternative non-forced-choice (4ANFC)] task were determined at 20 degrees, 30 degrees, 40 degrees, and 60 degrees eccentricity. Subsequently, near-threshold discrimination performance of Gabor pattern orientation without versus with a ring-shaped cue was measured at the same positions. The same Gabor patterns were then presented embedded in a random-dot flow field, and uncued discrimination performance was compared with performance after presentation of a relative-motion cue (RMC), ie a small random-dot field with motion in the opposite direction of the flow field. Both the conventional ring cue and the RMC induced significantly increased discrimination performance at all test locations. With the parameters chosen for this study, the RMC was slightly less effective than the conventional cue, but its effects were somewhat more pronounced in the far periphery of the visual field. Thus, relative motion is a powerful cue to attract attention to peripheral visual objects and improves performance as effectively as a conventional ring cue. The findings have practical relevance for everyday life, in particular for tasks like driving and navigation.     

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.     

Investigating the visual span in comparative search: the effects of task difficulty and divided attention

In three experiments, participants' visual span was measured in a comparative visual search task in which they had to detect a local match or mismatch between two displays presented side by side. Experiment 1 manipulated the difficulty of the comparative visual search task by contrasting a mismatch detection task with a substantially more difficult match detection task. In Experiment 2, participants were tested in a single-task condition involving only the visual task and a dual-task condition in which they concurrently performed an auditory task. Finally, in Experiment 3, participants performed two dual-task conditions, which differed in the difficulty of the concurrent auditory task. Both the comparative search task difficulty (Experiment 1) and the divided attention manipulation (Experiments 2 and 3) produced strong effects on visual span size.     

跨通道语义启动对视觉注意的影响

采用生活中的真实客体,我们考察了跨通道语义相关性对视觉注意的影响以及跨通道促进的时程。结合启动范式和点探测范式,实验1发现在听觉启动600毫秒后,被试对高相关视觉刺激的反应比对低相关刺激的反应更快,而在视觉启动下没有发现启动效应。实验2发现在启动刺激呈现900毫秒后跨通道启动效应消失。我们的研究证明了基于先前经验的视、听语义相关能够促进视觉的选择性注意。     

Attention is required for maintenance of feature binding in visual working memory

Working memory and attention are intimately connected. However, understanding the relationship between the two is challenging. Currently, there is an important controversy about whether objects in working memory are maintained automatically or require resources that are also deployed for visual or auditory attention. Here we investigated the effects of loading attention resources on precision of visual working memory, specifically on correct maintenance of feature-bound objects, using a dual-task paradigm. Participants were presented with a memory array and were asked to remember either direction of motion of random dot kinematograms of different colour, or orientation of coloured bars. During the maintenance period, they performed a secondary visual or auditory task, with varying levels of load. Following a retention period, they adjusted a coloured probe to match either the motion direction or orientation of stimuli with the same colour in the memory array. This allowed us to examine the effects of an attention-demanding task performed during maintenance on precision of recall on the concurrent working memory task. Systematic increase in attention load during maintenance resulted in a significant decrease in overall working memory performance. Changes in overall performance were specifically accompanied by an increase in feature misbinding errors: erroneous reporting of nontarget motion or orientation. Thus in trials where attention resources were taxed, participants were more likely to respond with nontarget values rather than simply making random responses. Our findings suggest that resources used during attention-demanding visual or auditory tasks also contribute to maintaining feature-bound representations in visual working memory—but not necessarily other aspects of working memory.     

Switching in the cocktail party: exploring intentional control of auditory selective attention

Using a novel variant of dichotic selective listening, we examined the control of auditory selective attention. In our task, subjects had to respond selectively to one of two simultaneously presented auditory stimuli (number words), always spoken by a female and a male speaker, by performing a numerical size categorization. The gender of the task-relevant speaker could change, as indicated by a visual cue prior to auditory stimulus onset. Three experiments show clear performance costs with instructed attention switches. Experiment 2 varied the cuing interval to examine advance preparation for an attention switch. Experiment 3 additionally isolated auditory switch costs from visual cue priming by using two cues for each gender, so that gender repetition could be indicated by a changed cue. Experiment 2 showed that switch costs decreased with prolonged cuing intervals, but Experiment 3 revealed that preparation did not affect auditory switch costs but only visual cue priming. Moreover, incongruent numerical categories in competing auditory stimuli produced interference and substantially increased error rates, suggesting continued processing of task-relevant information that often leads to responding to the incorrect auditory source. Together, the data show clear limitations in advance preparation of auditory attention switches and suggest a considerable degree of inertia in intentional control of auditory selection criteria.     

不确定性和预期有效性对运动方向感知决策的影响

环境中的运动刺激往往多变, 更好的方向感知需要同时依赖当前信息和先验信息。然而, 当前刺激的不确定性与先验线索的预期有效性在运动方向感知决策中如何整合尚不清楚。研究采用随机点运动范式, 要求被试判断散点群的整体运动方向, 方向一致的散点为相干点, 其比例越低, 不确定性越高。实验1比较了不同相干点比例下的感知准确度。根据实验1的结果, 选出20%和60%的相干点比例分别对应实验2中散点群的高、低不确定性水平。实验2比较了高、低不确定性和高、低预期有效性(线索正确预测目标的概率)下的感知准确度。结果发现, 随着不确定性的降低和预期有效性的增加, 感知准确度显著提高; 预期效应(高、低有效性下感知准确度的差异)随不确定性的提高而增加。结果表明, 先验信息与感觉信息能在运动方向感知决策中整合。研究为双重控制机制(DMC)理论下主动性与反应性控制协同工作的观点提供了实证支持, 并为交通事故的解释与预防提供了理论依据。     

Disengaging attention: on the locus of the cue-duration effect in partial report.

Increasing cue duration impairs performance in bar-probe partial report when cues are presented peripherally, but not centrally (P. Dixon, R. Gordon, A. Leung, & V. Di Lollo, 1997). Three experiments examined whether this cue-duration effect reflects processes of exogenous attention. The effect of cue duration on partial report performance with peripheral, but not central, cues was replicated (Experiment 1). Further experiments manipulated the degree that exogenous versus endogenous modes of selection were favored and found that the cue-duration effect for peripheral cues was reduced (a) when blocks contained a high proportion of central cues (Experiment 2) and (b) when the color of the cue indicated the location of the target (Experiment 3). These findings challenge the view that the cue-duration effect is restricted to exogenous attention and are discussed in terms of the process of disengaging attention from the cue to reallocate attention to the target representation.     

Cognitive load modulates attentional capture by color singletons during effortful visual search

Color singletons that are irrelevant to locating a visual target do not typically capture attention if visual search is effortful. In contrast, when search is efficient color singletons are often found to capture attention. Such distraction by a color singleton can be modulated by single-task vs. dual-task manipulations when visual search is efficient. This is due, presumably, to the increased cognitive load in the dual-task condition, which interferes with top-down attentional control. This study investigated whether capture by a color singleton is also modulated by single-task vs. dual-task manipulations when visual search was effortful. The results of three experiments revealed that attentional capture effects were absent in a single-task condition and were present in a dual-task condition, but only when the identity of the color singleton is not associated with the target response-set. When the identity of the color singleton was relevant to the response-set it captured attention in both the single-task and in dual-task conditions.     

Is location cueing inherently superior to color cueing? Not if color is presented early enough

A possible source for the advantage of location cueing over non-spatial cueing is that orienting attention by a location cue is feasible prior to stimulus onset, whereas that is normally not the case with orienting by a non-spatial cue. To examine how critical that source is for observing an advantage, we eliminated it: In a color-preview condition, subjects were to detect a target presented on the background of one of two differently colored circles (where color-location assignment was random). In a no-preview condition, the circles were both gray, but the target was either red or green (where color assignment was random). Cue type (location vs color) was also manipulated. The color preview in Experiment 1 (in which color onset preceded cue onset) was found helpful: Whereas a substantial disparity in validity effects of the two cue types was obtained with no preview, no significant difference was found when a color preview was introduced. The validity effects of both cue types were found to be about the same also in Experiment 2, in which color onset was exactly synchronized with cue onset, and SOA was manipulated. Furthermore, the absence of an SOA x cue type interaction indicated that the time course of the color cue validity did not lag after the time course of the location cue validity, which seems incompatible with the hypothesis that a color cue cannot affect orienting without first computing a location from it prior to cue onset. Overall, the results suggest that the time course of color cueing is not inherently different from that of location cueing once its main disadvantages are removed.     

The comprehension of action-related sentences may cause interference rather than facilitation on matching actions

This study used a dual-task paradigm to analyze the time course of motor resonance during the comprehension of action language. In the study, participants read sentences describing a transfer either away from (“I threw the tennis ball to my rival”) or toward themselves (“My rival threw me the tennis ball”). When the transfer verb appeared on the screen, and after a variable stimulus onset asynchrony (SOA), a visual motion cue (Experiment 1) or a static cue (Experiment 2) prompted participants to move their hand either away from or toward themselves to press a button. The results showed meaning–action interference at short SOAs and facilitation at the longest SOA for the matching conditions. These results support the hypothesis that motor processes associated with the comprehension of action-related language interfere with an overlapping motor task, whereas they facilitate a delayed motor task. These effects are discussed in terms of resonance processes in the motor cortex.