Spatial acuity and summation on the hand: The role of thermal cues in material discrimination

The spatial characteristics of thermal perception were studied in two experiments that examined how thermal stimuli are processed within the hands. A thermal display that simulates cues associated with making contact with different materials was used in these studies. In the first experiment, participants indicated which of two simulated materials that were presented to the index fingertip was cooler. The results indicated that participants were unable to resolve the two areas of thermal stimulation. In the second experiment, the effects of concurrent thermal stimulation on the ability to discriminate between simulated materials were evaluated. Thermal cues were presented to the middle fingers of both hands and to two adjacent fingers on one hand. Thermal spatial summation was evident across the fingers, which enhanced the ability to discriminate between materials when the cooler stimulus was presented to three fingers. When the same stimulus was presented to the two hands, the stimulation of adjacent fingers altered the perceived thermal response.     

Transient attention degrades perceived apparent motion

Transient spatial attention refers to the automatic selection of a location that is driven by the stimulus rather than a voluntary decision. Apparent motion is an illusory motion created by stationary stimuli that are presented successively at different locations. In this study we explored the effects of transient attention on apparent motion. The motion target presentation was preceded by either valid attentional cues that attract attention to the target location in advance (experiments 1-4), neutral cues that do not indicate a location (experiments 1, 3, and 4), or invalid cues that direct attention to a non-target location (experiment 2). Valid attentional cues usually improve performance in various tasks. Here, however, an attentional impairment was found. Observers' ability to discriminate the direction of motion diminished at the cued location. Analogous results were obtained regardless of cue type: singleton cue (experiment 1), central non-informative cue (experiment 2), or abrupt onset cue (experiment 3). Experiment 4 further demonstrated that reversed apparent motion is less likely with attention. This seemingly counterintuitive attentional degradation of perceived apparent motion is consistent with several recent findings, and together they suggest that transient attention facilitates spatial segregation and temporal integration but impairs spatial integration and temporal segregation.     

The effects of transient attention on spatial resolution and the size of the attentional cue

It has been shown that transient attention enhances spatial resolution, but is the effect of transient attention on spatial resolution modulated by the size of the attentional cue? Would a gradual increase in the size of the cue lead to a gradual decrement in spatial resolution? To test these hypotheses, we used a texture segmentation task in which performance depends on spatial resolution, and systematically manipulated the size of the attentional cue: A bar of different lengths (Experiment 1) or a frame of different sizes (Experiments 2-3) indicated the target region in a texture segmentation display. Observers indicated whether a target patch region (oriented line elements in a background of an orthogonal orientation), appearing at a range of eccentricities, was present in the first or the second interval. We replicated the attentional enhancement of spatial resolution found with small cues; attention improved performance at peripheral locations but impaired performance at central locations. However, there was no evidence of gradual resolution decrement with large cues. Transient attention enhanced spatial resolution at the attended location when it was attracted to that location by a small cue but did not affect resolution when it was attracted by a large cue. These results indicate that transient attention cannot adapt its operation on spatial resolution on the basis of the size of the attentional cue.     

Spatial distribution of attentional bias in visuo-spatial working memory following multiple cues

When attention is focused on one location, its spatial distribution depends on many factors, such as the distance between the attended location and the target location, the presence of visual meridians in between them, and the way, endogenous or exogenous, by which attention is oriented. However, it is not well known how attention distributes when more than one location is endogenously or exogenously cued, which was the focus of the current study. Furthermore, the distribution of attention has been manly investigated in perception. In the present study we faced this issue from a different perspective, by examining the spatial distribution of the attentional bias in visuo-spatial working memory (VSWM), when attention is oriented either exogenously or endogenously, i.e., after two peripheral vs. central symbolic cues (also manipulating cue–target predictability). Results indicated a systematic difference between endogenous and exogenous attention regarding the distribution of the attentional bias over VSWM. In fact, attentional bias following endogenous cues was affected by the presence of visual meridians and by the split of the attentional focus, converging in a unipolar attentional distribution, independently of cue–target predictability. On the other hand, when pulled by exogenous cues, attention distributed uni-modally or multi-modally depending on the distance between the cued locations, with larger effects for highly predictive cues. Results are discussed in terms of space-based, object-based and perceptual grouping mechanisms.     

The benefit of attention is not diminished when distributed over two simultaneous cues

Recent findings have suggested that transient attention can be triggered at two locations simultaneously. However, it is unclear whether doing so reduces the effect of attention at each attended location. In two experiments, we explored the consequences of dividing attention. In the first experiment, we compared the effects of one or two cues against an uncued baseline to determine the consequences of dividing attention in a paradigm with four rapid serial visual presentation (RSVP) streams. The results indicated that two simultaneous cues increase the accuracy of reporting two targets by almost the same amount as a single cue increases the report of a single target. These results suggest that when attention is divided between multiple locations, the attentional benefit at each location is not reduced in proportion to the total number of cues. A consequent prediction of this finding is that the identification of two RSVP targets should be better when they are presented simultaneously rather than sequentially. In a second experiment, we verified this prediction by finding evidence of lag-0 sparing: Two targets presented simultaneously in different locations were reported more easily than two targets separated by 100 ms. These findings argue against a biased-competition theory of attention. We suggest that visual attention, as triggered by a cue or target, is better described by a convergent gradient-field attention model.     

眼睛注视线索提示效应: 内源性注意还是外源性注意?

采用改进的Posner视-空间线索提示范式, 对眼睛注视线索提示效应(eyes gaze cueing effect)的加工机制进行了探讨。实验一考察注视提示线索对空间Stroop效应的影响; 实验二考察注视提示线索对特征抽取和特征整合的影响。实验结果显示: 注视线索提示有效时的空间Stroop效应显著大于提示无效的情景; 在单一特征搜索与特征联合搜索任务中, 注视线索提示效应无差别。这说明, 注视线索通过在头脑里形成空间方位表征诱导注意转移; 注视线索通过影响特征抽取、而非特征整合阶段, 对客体加工产生易化。本研究支持注视线索提示效应属于内源性注意的观点。     

暂时建立的自我参照线索对返回抑制的影响

采用经典线索-靶子范式,考察了暂时建立的自我参照线索对返回抑制（inhibition of return, IOR）效应量的调节作用。结果发现,在暂时建立的朋友参照线索或无意义线索条件下均产生了IOR效应,但是在暂时建立的自我参照线索条件下IOR效应没有出现,这是因为相比暂时建立的朋友参照线索或无意义线索,被试对呈现在暂时建立的自我参照线索后的靶刺激的反应更快。结果表明,自我相关信息能够削弱IOR的效应量,并为IOR是一种进化适应性的视觉搜索促进机制提供了新的证据。     

Perceptual grouping in change detection

Detection of an item's changing of its location from one instance to another is typically unaffected by changes in the shape or color of contextual items. However, we demonstrate here that such location change detection is severely impaired if the elongated axes of contextual items change orientation, even though individual locations remain constant and even though the orientation was irrelevant to the task. Changing the orientations of the elongated stimuli altered the perceptual organization of the display, which had an important influence on change detection. In detecting location changes, subjects were unable to ignore changes in orientation unless additional, invariant grouping cues were provided or unless the items changing orientation could be actively ignored using feature-based attention (color cues). Our results suggest that some relational grouping cues are represented in change detection even when they are task irrelevant.     

The role of spatial attention and other processes on the magnitude and time course of cueing effects

We are quite often exposed to multiple objects present in the visual scene, thus attentional selection is necessary in order to selectively respond to the relevant information. Objects can be selected on the basis of the location they occupy by orienting attention in space. In this paper, we review the evidence showing that attention can be oriented in space either endogenously, on the basis of central cues, predictive of the relevant location, or exogenously, automatically triggered by the salient properties of visual stimuli (peripheral cues). Several dissociations observed between orienting on the basis of the two types of cues have led to the conclusion that they do not represent just two modes of triggering the orienting of the very same attentional mechanism, but rather they modulate processing differently. We present a theoretical framework according to which endogenous predictive cues facilitate target processing by orienting attention, thus amplifying processing at the attended location. In contrast, apart from attentional orienting, peripherally presented discrepant cues might trigger additional cue-target event-integration and event-segregation processes, which modulate processing in a different way, thus leading to cueing effects that are exclusively triggered by peripheral cues.     

Does attention have different effects on line orientation and line arrangement discrimination?

Visual search and texture segregation studies have led to the inference that stimuli differing in the orientation of their component line segments can be distinguished without focal attention, whereas stimuli that differ only in the arrangement of line segments cannot. In most of this research, the locus of attention has not been explicitly manipulated. In the first experiment presented here, attention was directed to a relevant peripheral target by a cue presented near the target location or at the fovea. Effects of attention on orientation discrimination were assessed in a two-alternative forced-choice task with targets that were either: (1) lines that slanted obliquely to the right or left, or were horizontal or vertical, or (2) Y-like targets that had a short arm leading obliquely right or left of a vertical line. In some groups, a four-alternative forced-choice test with lines at 0°, 45°, 90°, and 135° orientations was used. Discrimination of these targets (i.e. targets that differ in the orientation of component line segments) was only minimally facilitated as the time between the onset of the valid cue and the onset of the target (cue-target stimulus onset asynchrony, SOA) was increased from 0 or 17 msec to 267 msec. In contrast, discrimination of targets that did not differ in the orientation of component line segments but differed in line arrangement (T-like characters), was greatly facilitated by longer cue-target SOAs. In Experiment 2, a cue misdirected attention on 20% of the trials. A decrement occurred on incorrectly cued trials in comparison to correctly cued trials for both types of stimuli used (lines and Ts). The results from these experiments suggest that discrimination of line orientation benefits less from focal attention than does discrimination of line arrangement, but that both discriminations suffer when attention must be disengaged from an irrelevant spatial location.     

跨感觉通道任务中刺激驱动注意捕获的不对称性

通过两个实验探讨了来自不同感觉通道或不同空间方位的奇异刺激在视听搜索范式中的注意捕获。实验一使用定位任务探讨刺激驱动注意捕获中跨通道效应且及其不对称性, 结果发现, 当靶子在听觉通道时, 只有来自听觉同侧空间方位的奇异刺激成功的捕获了注意; 而来自视觉同侧空间和异侧空间的奇异刺激并没有捕获注意。实验二使用检测任务进一步探讨刺激驱动的注意捕获中的跨通道效应且具有不对称性, 结果发现, 来自同侧和异侧的听觉奇异刺激均捕获了注意, 但是视觉奇异刺激却不能捕获注意。研究表明, 视听搜索范式中的奇异刺激的注意捕获具有不对称性, 且存在着一种超感觉通道的注意资源。     

Textures shape the attentional focus: Evidence from exogenous and endogenous cueing

The spatial cueing paradigm (Posner Quarterly Journal of Experimental Psychology 32:3–25, 1980) has often been used to investigate the time course of the deployment of visual attention in space. In a series of eight experiments we investigated whether spatial cues would not only enhance processing of stimuli presented at cued locations, but also enhance processing of the entire texture in which the stimuli were presented. Results showed highest accuracy for responses to stimuli presented at cued locations, a replication of the traditional cueing effect (Posner 1980). Additionally, stimuli presented at uncued locations were responded to with higher accuracy when they were presented inside the same texture as the cued location, as compared with stimuli presented outside the texture with the cued location. To investigate this texture advantage for both automatic and voluntary attention deployment, exogenous and endogenous cues were used. The texture advantage was observed for short interstimulus intervals (ISIs) of 50 and 100 ms for exogenous cues and for a longer ISI of 200 ms for endogenous cues. These findings indicate that the arrangement of task-irrelevant visual stimuli also can have a large impact on the cueing effect. This suggests that visual spatial attention spreads texture-wise across the visual field. Control experiments revealed that the homogeneity within texture elements contributes most to the effect but that the texture advantage is a function of both orientation contrast at the texture border and homogeneity within texture elements.     

Effects of location and form cuing on the allocation of attention in the visual field

Two experiments were conducted which tested the effect of two different types of cues on the allocation of attention in the visual field. Subjects responded to a target appearing either 6.5 degrees to the right or to the left of fixation in a field filled with small randomly positioned line segments. The target form was either a circle or diamond in which a horizontal or vertical line segment was positioned. Subjects made a speeded discrimination response on the basis of the orientation of this line segment. In the first experiment, there was always one target at each trial. In the second experiment, both circle and diamond were presented left or right of fixation simultaneously whereby the line segment only appeared in one of the forms. In different conditions, the most likely target location (left or right) and form (circle or diamond) were cued. Control conditions served as a baseline for determining costs and benefits. Reaction time measures showed that the validity of the location cue resulted in both costs and benefits, whereas the validity of the form cue had no such effects. The results cannot be reconciled with the claim of zoom lens theories that spatial attention can switch between different modes of operations. They are also at odds with theories that claim that attention has no spatial locus. The results are consistent with a simple spotlight theory in which spatial attention involves selecting a particular restricted area of the visual field for which the perceptual efficiency is enhanced.     

What variety of attention is automatically captured by peripheral cues?

Previous studies have shown that the voluntary allocation of attention to a location in space can influence accuracy in two ways. First, additional processing resources can be allocated to the attended location, leading to an improvement in perceptual quality for objects presented at that location. Second, decision processes can be restricted to information arising from the attended location, which improves accuracy without influencing the perceptual representation. The present study examined the operation of these two attentional mechanisms when nonpredictive peripheral cues were used to capture attention automatically. Experiment 1 showed that, like predictive cues, nonpredictive cues influence accuracy by summoning perceptual resources and also by influencing decision processes. However, both the cues and the targets in this experiment were defined by luminance increments, making it possible that the cuing effects were mediated by a task-controlled attentional set rather than being fully automatic. Experiments 2 and 3 examined this possibility by using luminance-defined cues and color-defined targets; evidence was again obtained for both perceptual-level and decision-level attention effects. The capture of attention by a nonpredictive peripheral cue thus appears to influence both perceptual resource allocation and postperceptual decision processes.     

The coupling between spatial attention and other components of task-set: A task-switching investigation

Is spatial attention reconfigured independently of, or in tandem with, other task-set components when the task changes? We tracked the eyes of participants cued to perform one of three digit-classification tasks, each consistently associated with a distinct location. Previously we observed, on task switch trials, a substantial delay in orientation to the task-relevant location and tendency to fixate the location of the previously relevant task—“attentional inertia”. In the present experiments the cues specified (and instructions emphasized) the relevant location rather than the current task. In Experiment 1, with explicit spatial cues (arrows or spatial adverbs), the previously documented attentional handicaps all but disappeared, whilst the performance “switch cost” increased. Hence, attention can become decoupled from other aspects of task-set, but at a cost to the efficacy of task-set preparation. Experiment 2 used arbitrary single-letter cues with instructions and a training regime that encouraged participants to interpret the cue as indicating the relevant location rather than task. As in our previous experiments, and unlike in Experiment 1, we now observed clear switch-induced attentional delay and inertia, suggesting that the natural tendency is for spatial attention and task-set to be coupled and that only quasi-exogenous location cues decouple their reconfiguration.     

Is Posner's "beam" the same as Treisman's "glue"?: On the relation between visual orienting and feature integration theory

In the present study we investigated whether the visually allocated "beam" studied by Posner and others is the same visual attentional resource that performs the role of feature integration in Treisman's model. Subjects were cued to attend to a certain spatial location by a visual cue, and performance at expected and unexpected stimulus locations was compared. Subjects searched for a target letter (R) with distractor letters that either could give rise to illusory conjunctions (PQ) or could not (PB). Results from three separate experiments showed that orienting attention in response to central cues (endogenous orienting) showed similar effects for both conjunction and feature search. However, when attention was oriented with peripheral visual cues (exogenous orienting), conjunction search showed larger effects of attention than did feature search. It is suggested that the attentional systems that are oriented in response to central and peripheral cues may not be the same and that only the latter performs a role in feature integration. Possibilities for future research are discussed.     

Perceiving crowd attention: Gaze following in human crowds with conflicting cues

People automatically redirect their visual attention by following others’ gaze orientation, a phenomenon called “gaze following.” This is an evolutionarily generated socio-cognitive process that provides people with information about their environments. Often, however, people in crowds can have rather different gaze orientations. This study investigated how gaze following occurs in situations with many conflicting gazes. In two experiments, we modified the gaze cueing paradigm to use a crowd rather than a single individual. Specifically, participants were presented with a group of human avatars with differing gaze orientations, and the target appeared randomly on the left or right side of a display. We found that (a) when a marked difference existed in the number of avatars with divergent gaze orientations, participants automatically followed the majority’s gaze orientation, and (b) the strongest gaze cue effect occurred when all gazes shared the same orientation, with the response superiority of the majority’s oriented location monotonically diminishing with the number of gazes with divergent orientations. These findings suggested that the majority rule plays a role in gaze following behavior when individuals are confronted with conflicting multigaze scenes, and that an increasing subgroup size appears to enlarge the strength of the gaze cueing effect.     

Spatial attention can be biased towards an expected dimension

A commonly held view in both exogenous and endogenous orienting is that spatial attention is associated with enhanced processing of all stimuli at the attended location. However, we often search for a specific target at a particular location, so an observer should be able to jointly specify the target identity and expected location. Whether attention can bias dimension-specific processes at a particular location is not yet clear. We used a dual task to examine the effects of endogenous spatial cues on the accuracy of perceptual judgments of different dimensions. Participants responded to a motion target and a colour target, presented at the same or different locations. We manipulated a central cue to predict the location of the motion or colour target. While overall performance in the two tasks was comparable, cueing effects were larger for the target whose location was predicted by the cue, implying that when attending a particular location, processing of the likely dimension was preferentially enhanced. Additionally, an asymmetry between the motion and colour tasks was seen; motion was modulated by attention, and colour was not. We conclude that attention has some ability to select a dimension at a particular location, indicating integration of spatial and feature-based attention.     

Effects of orientation-selective adaptation on the Z?llner illusion

The model of inhibitory interaction between orientation detectors was examined by prolonged presentation of grating patterns (which was expected to induce orientation-selective adaptation) before measurement of the Z?llner illusion. Adaptation effects were measured under conditions which excluded intrusion by the tilt aftereffect. In experiment 1, illusion magnitude greatly decreased only when the orientation of the adapting grating was the same as that of the inducing lines, which confirmed the first prediction deduced from the model. There was no effect of adapting grating when it was oriented more than 20 degrees away from the inducing lines. In experiment 2, adaptation effects were selective not only to orientation but also to spatial frequency. In experiment 3 it was shown that illusion reduction was mediated neither by lowered apparent contrast of the inducing lines nor by retinal adaptation. The results are discussed with respect to the nature of adaptation and possible physiological correlates.     

Does previewing one stimulus feature help conjunction search?

We examined the effects of previewing one aspect of a search display, in order to determine what subset of display information is most useful as a prelude to a search task. Observers were asked to indicate the presence or absence of a known target, in a conjunction search where the target was defined by the combination of colour and orientation (a yellow horizontal line presented among yellow vertical and pink horizontal distractors). In the colour preview condition of experiment 1, observers were first shown a 1 s preview of the locations and colours of the search items before the actual search set was presented. That is, search items first appeared as yellow and pink squares for 1 s, which each then turned into yellow and pink oriented lines (in the same locations) which comprised the display to be searched. In the orientation preview condition, observers were first shown a 1 s preview of the locations and orientations of the search items before the actual search display was presented. These two conditions were compared to a control condition consisting of standard conjunction search without any preview display. There was no effect of colour preview; there was a marginal effect of orientation preview, but in the opposite direction from what was expected reaction time increased for orientation preview searches. In experiment 2 these previews were compared to two spatial cueing conditions; in this experiment the colour preview did provide a small amount of help. Finally, in experiment 3 both previews were presented in succession, and increased facilitation was found, in particular when the colour preview preceded the orientation preview. These findings are discussed in relation to the literature, in particular the Guided Search model (Wolfe et al 1989 Journal of Experimental Psychology: Human Perception and Performance 15 419-433; Wolfe 1994 Psychonomic Bulletin & Review 1 202-238).