Time course of visual attention with emotional faces

When a briefly presented and then masked visual object is identified, it impairs the identification of the second target for several hundred milliseconds. This phenomenon is known as attentional blink or attentional dwell time. The present study is an attempt to investigate the role of salient emotional information in shifts of covert visual attention over time. Two experiments were conducted using the dwell time paradigm, in which two successive targets are presented at different locations with a variable stimulus onset asynchrony (SOA). In the first experiment, real emotional faces (happy/sad) were presented as the first target, and letters (L/T) were presented as the second target. The order of stimulus presentation was reversed in the second experiment. In the first experiment, identification of the letters preceded by happy faces showed better performance than did those preceded by sad faces at SOAs less than 200 msec. Similarly, happy faces were identified better than sad faces were at short SOAs in Experiment 2. The results show that the time course of visual attention is dependent on emotional content of the stimuli. The findings indicate that happy faces are associated with distributed attention or broad scope of attention and require fewer attentional resources than do sad faces.     

Attentional sensitization of unconscious visual processing: Top-down influences on masked priming

Classical theories of automaticity assume that automatic processes elicited by unconscious stimuli are autonomous and independent of higher-level cognitive influences. In contrast to these classical conceptions, we argue that automatic processing depends on attentional amplification of task-congruent processing pathways and propose an attentional sensitization model of unconscious visual processing: According to this model, unconscious visual processing is automatic in the sense that it is initiated without deliberate intention. However, unconscious visual processing is susceptible to attentional top-down control and is only elicited if the cognitive system is configured accordingly. In this article, we describe our attentional sensitization model and review recent evidence demonstrating attentional influences on subliminal priming, a prototypical example of an automatic process. We show that subliminal priming (a) depends on attentional resources, (b) is susceptible to stimulus expectations, (c) is influenced by action intentions, and (d) is modulated by task sets. These data suggest that attention enhances or attenuates unconscious visual processes in congruency with attentional task representations similar to conscious perception. We argue that seemingly paradoxical, hitherto unexplained findings regarding the automaticity of the underlying processes in many cognitive domains can be easily accommodated by our attentional sensitization model. We conclude this review with a discussion of future research questions regar-ding the nature of attentional control of unconscious visual processing.     

Space-, object-, and feature-based attention interact to organize visual scenes

Biased-competition accounts of attentional processing propose that attention arises from distributed interactions within and among different types of perceptual representations (e.g., spatial, featural, and object-based). Although considerable research has examined the facilitation in processing afforded by attending selectively to spatial locations, or to features, or to objects, surprisingly little research has addressed a key prediction of the biased-competition account: that attending to any stimulus should give rise to simultaneous interactions across all the types of perceptual representations encompassed by that stimulus. Here we show that, when an object in a visual display is cued, space-, feature-, and object-based forms of attention interact to enhance processing of that object and to create a scene-wide pattern of attentional facilitation. These results provide evidence to support the biased-competition framework and suggest that attention might be thought of as a mechanism by which multiple, disparate bottom-up, and even top-down, visual perceptual representations are coordinated and preferentially enhanced.     

Concurrent processing of spatial relations and objects in two cerebral hemispheres

This study examined hemispheric asymmetry for concurrent processing of object and spatial information. Participants viewed two successive stimuli, each of which consisted of two digits and two pictures that were randomly located and judged them as identical or different. A sample stimulus was presented in a central visual field, followed by a matching stimulus presented briefly in a left or right visual field. The matching stimuli were different from the sample stimuli with respect to the object (digit or picture) or spatial (locations or distances of items) aspect. No visual field asymmetry was found in the detection of object change. However, a left visual field advantage was found in the detection of spatial change. This result can be explained by the double filtering by frequency theory of Ivry and Robertson, who asserted that the left hemisphere has a bias for processing information contained in relatively high spatial frequencies whereas the right hemisphere has a bias for processing information contained in relatively low spatial frequencies. Based upon this evidence, the importance of interhemispheric integration for visual scene perception is discussed.     

The beneficial effects of additional task load, positive affect, and instruction on the attentional blink

The attentional blink reflects the impaired ability to identify the 2nd of 2 targets presented in close succession--a phenomenon that is generally thought to reflect a fundamental cognitive limitation. However, the fundamental nature of this impairment has recently been called into question by the counterintuitive finding that task-irrelevant mental activity improves attentional blink performance (C. N. L. Olivers & S. Nieuwenhuis, 2005). The present study found a reduced attentional blink when participants concurrently performed an additional memory task, viewed pictures of positive affective content, or were instructed to focus less on the task. These findings support the hypothesis that the attentional blink is due to an overinvestment of attentional resources in stimulus processing, a suboptimal processing mode that can be counteracted by manipulations promoting divided attention.     

Varieties of size-specific visual selection

Compared time to evaluate stimuli of varying sizes. When Ss expect an upcoming stimulus to be a certain size, response time increases with the disparity between expected and actual size. There are, however, 2 size adjustment processes, and they reflect 2 types of visual selection. In the first, a shape-specific image representation is used to separate a visual object from a superimposed distractor. These representations require the type of slow size scaling demonstrated in imagery experiments. The second size scaling process is faster and not shape-specific. At any given time the visual system is set to process information at a particular scale, and that scale can be adjusted to match an object's size. Because both selection mechanisms depend on size, they probably occur at a relatively low, spatially organized processing level. These findings lead to a new explanation for results that had been taken as evidence for attentional selection at the level of object representations.     

The role of attention and study time in explicit and implicit memory for unfamiliar visual stimuli

The effects of limited attentional resources and study time on explicit and implicit memory were studied using Schacter and Cooper’s possible and impossible objects in their recognition and object decision paradigm. In one experiment, when attention at study was limited by a flanking digits procedure, object recognition was diminished but object decision priming for possible objects was unaffected; in another experiment, limiting attention plus reducing stimulus study time impaired object recognition and eliminated object priming. Recognition memory and perceptual priming for previously unfamiliar visual stimuli were both influenced by attention, although to different degrees. The intervening variable of study time determined the degree to which priming was affected by attentional resources. These results support a limited capacity attentional model for both recognition and perceptual priming of unfamiliar visual stimuli, and they highlight the need for assessing the interaction of attentional resources and study time in explicit and implicit memory tasks.     

Space, object, and task selection

Within the field of selective attention, two separate literatures have developed, one examining the effect of selection of objects and another examining the effect of selection of features. The present study bridged these two traditions by examining the compatibility effects generated by two features of attended and unattended nontarget (foil) stimuli. On each trial, participants determined either the identity or the orientation of a visual stimulus. Spatial attention was controlled using cues (presented prior to the target frame) designed to involuntarily capture attention. We independently manipulated the stimulus dimension the participants prepared for and the stimulus dimension on which they actually executed the task. Preparation had little influence on the magnitude of compatibility effects from foil stimuli. For attended stimuli, the stimulus dimension used in executing the task produced large compatibility effects, regardless of whether that dimension was prepared. These and other compatibility effects (e.g., Stroop effects) are discussed in relation to an integrative model of attentional selection. The key assumptions are that (1) selection occurs at three distinct levels (space, object, and task), (2) spatial attention leads to semantic processing of all dimensions, and (3) features do not automatically activate responses unless that object is selected for action.     

The modulation of the flash-lag effect by voluntary attention

In the flash-lag effect (FLE), a flashing object appears to lag behind a moving object when both happen to be physically aligned to each other. According to an earlier account of the FLE (Baldo and Klein 1995 Nature 378 565-566), this perceptual phenomenon would result from differential delays in the perceptual processing of moving and flashing stimuli, presumably involving attentional mechanisms. Here, we have attempted to demonstrate in a more convincing way the participation of voluntary attention as a major component of the FLE. In experiment 1 the observer's attentional set was induced by the spatial probability structure of the visual stimulus. A flashing dot (relative to which the location of a moving dot should be judged) was presented, in separate blocks, at fixed, alternating, or randomly chosen locations. The two former conditions, providing a higher spatial predictability, yielded a smaller FLE than the latter condition, which provided a lower spatial predictability of the flashing dot. In experiment 2 we employed a standard cueing procedure, in which a participant was instructed to shift covertly his/her attentional focus according to a symbolic cue. The cue indicated, with a validity of 80%, the visual hemifield at which the flashing dot would be presented. As predicted by our conceptual model, the mean magnitude of the FLE in the valid trials was significantly smaller than that found in the invalid ones. Therefore, both experiments provided strong evidence supporting the participation of voluntary attention in the FLE. Attentional mechanisms should be seen not as the primary cause of the FLE, but rather as an important modulatory component of a broader process whose spatiotemporal dynamics engenders the FLE and possibly other related phenomena. Even though we elected an account based on the influence of attention on perceptual latencies, our empirical findings are compatible with other theoretical models embraced by the current flash-lag controversy and should be accommodated by every attempt to explain this perceptual phenomenon.     

Object-based selection within and beyond the focus of spatial attention

In a series of experiments, we examined the effect of perceptual objects on visual attentional processing in the presence of spatially cued attentional selection. Subjects made speeded judgments about two visual elements that were either both on the same object or on two different objects. Judgments were faster when the elements were on the same object than when they were on different objects, revealing an object advantage. Importantly, the object advantage remained even when either exogenous or endogenous spatial cues were used to direct the subjects' attention to a part of the display, contrary to earlier findings of other researchers. The object advantage, however, did disappear when the stimulus duration was shortened substantially. The results show that object-based selection is pervasive and is not diminished by the act of selective attention. The results are discussed in terms of their implications for the mechanisms that underlie attentional selection.     

You can't stop new motion: Attentional capture despite a control set for colour

When a stationary object begins to move, visual spatial attention is reflexively deployed to the location of that object. We tested whether this capture of attention by new motion is entirely stimulus driven, or whether it is contingent on an observer's goals. Participants monitored a visual display for a colour change, inducing an attentional control set (ACS) for colour. Across the three performed experiments, irrelevant new-motion cues always captured visual spatial attention, despite the ACS for colour. This persistence of the attentional cueing effect demonstrates that ACSs, in particular an ACS for colour, cannot prevent new motion from capturing attention. Unlike other stimulus types, such as luminance changes, colour singletons, and new objects, new motion may always capture attention regardless of an observer's goals. This conclusion entails that new motion is an important determinant of when, and to where, visual spatial attention is deployed.     

The attentional cost of inattentional blindness

When our attention is engaged in a visual task, we can be blind to events which would otherwise not be missed. In three experiments, 97 out of the 165 observers performing a visual attention task failed to notice an unexpected, irrelevant object moving across the display. Surprisingly, this object significantly lowered accuracy in the primary task when, and only when, it failed to reach awareness. We suggest that an unexpected stimulus causes a state of alert that would normally generate an attentional shift; if this response is prevented by an attention-consuming task, a portion of the attentional resources remains allocated to the object. Such a portion is large enough to disturb performance, but not so large that the object can be recognized as task-irrelevant and accordingly ignored. Our findings have one counterintuitive implication: irrelevant stimuli might hamper some types of performance only when perceived subliminally.     

Allocation of attention in the visual field

This research investigated whether attentional resources can be simultaneously allocated to several locations in a visual display, whether the mode of processing (serial or parallel) can be switched within a trial, and the nature of the costs when attentional resources are concentrated on an invalid location. Subjects were required to determine which of two target letters was present in eight-letter circular displays. In precue conditions, a primary and a secondary target location were designated 150 ms before target onset by an indicator that varied in validity. In the control conditions no cue was provided. A second experiment verified several assumptions that had been made in interpreting the data of Experiment 1. Modifications in Jonides' (1983) two-process model were suggested in terms of a zoom lens model of attentional resources. Instead of two alternative processing modes, attentional resources are conceived as capable of distribution over the visual field, but with low resolving power, or as continuously constricting to small portions of the visual field with a concomitant increase in processing power.     

Modulation of the Spatial Extent of the Attentional Focus in High-level Volleyball Players

In this study, we explored the ability of first league professional volleyball players to modulate the allocation of attentional resources in the visual space by adapting the size of the attentional focus. Like Castiello and Umilta (1990), we employed an experimental procedure that is a variation of Posner's (1980) paradigm for exploring covert orienting of visuospatial attention. In a signalled reaction time task, a peripheral cue of varying size was presented unilaterally or bilaterally of a central fixation point, followed by a target at different stimulus onset asynchronies. The target could occur validly inside the cue or invalidly outside it with varying spatial relation to its boundary. Our results suggest that volleyball players are better able than controls to modulate the distribution of attentional resources within and around peripherally cued areas. Moreover, volleyball players seem to be able to flexibly adapt the gradient of attentional resources around the cued area, as would be expected from their sport practice.     

Automatic and voluntary focusing of attention

In this study, we investigate whether attentional focusing, like attentional orienting, comprises two independent mechanisms. We provide direct empirical evidence in favor of the existence of two mechanisms--one exogenous, or automatic, and one endogenous, or voluntary--that play a role in adjusting the size of the focus of attention. When a new object suddenly occurs in the visual field, the focus is first automatically fitted to it, and then an endogenous effort has to be exerted to maintain attention in the focused mode. Also, we provide evidence that voluntary focusing needs a perceptual object in order to operate.     

Auditory attentional blink: masking the second target is necessary, delayed masking is sufficient.

When two target items (T1 and T2) are presented in rapid succession among fillers, processing T2 is often impaired. This phenomenon is known as the attentional blink (AB). Within the visual modality, this second-target deficit generally occurs only if T2 is masked by a trailing item. The current study was designed to examine whether masking of T2 also plays a critical role in the auditory AB. Results showed a reliable AB effect even when the item following T2 was replaced by silence. However, the AB deficit was abolished when T2 was the last presented stimulus. Our results suggest that, as in vision, T2 masking is necessary for the AB to take place in audition, but that masking is effective even when delayed, providing evidence that the phenomenon shares some functional mechanisms across sensory modalities.     

Perception of visual letter strings in a case of left neglect: Manipulation of the word form

Patients with lesions in the right parietal lobe neglect the left side of nonwords much more than the left side of words. This has been interpreted in terms of a more automatic process in reading words. The case of a patient with left visual neglect after a vascular right parietooccipital lesion is presented. He showed the phenomenon of a word superiority effect over nonword in reading at the beginning in a clinical test with static cards; 6 months later, after some recovery, the same phenomenon could be demonstrated only with tachistoscopic presentation, and it occurred even inside the good right visual hemifield. The word form of visually presented stimuli was manipulated, showing that there was a striking effect particularly when spacing the letters of words in a task that requires naming the stimulus. The patient's performance is interpreted in terms of an attentional deficit occurring at an early level of spatial information processing.     

A comparison of dichotic and visuo-acoustic competition in hemispherectomized patients

Following hemispherectomy, patients performing dichotic listening tasks have great difficulty reporting items presented to the ear ipsilateral to their intact hemisphere. One possible cause is an attentional imbalance which, when competing inputs are received from both sides of space, restricts the patient's attention to the stimulus contralateral to his remaining hemisphere. If this explanation is true, then a similar ipsilateral ear decrement should occur when a competing visual stimulus is presented in the contralateral field. In the present study, however, hemispherectomy patients easily reported a digit presented to the ear ipsilateral to their intact hemisphere despite the concurrent presentation of a visual digit to their contralateral field.     

An inhibition effect in the temporal constrains of attentional selection: the Backward Blink

The study aims at investigating the dynamics of visual information processing during sequential control of attentional selection. By combining two different traditional paradigms we show for the first time that during rapid selection of visual targets, encoding of a new target stimulus is facilitated by suppression of the preceding relevant stimulus category (Backward Blink; BB). Such inhibition would operate to reduce interference from previously stored information, in order to facilitate the instantiation of a new attentional episode. Results suggest that the same underlying inhibitory mechanism might contribute to two different attentional effects, specifically, the switch cost and the Attentional Blink, suggesting a general inhibitory mechanism of attentional control, with broad implications for understanding how the brain perceives any task-relevant stimulus.     

Inhibition of return is composed of attentional and oculomotor processes

Response time can be delayed if a target stimulus appears at a location or object that was previously cued. This inhibition of return (IOR) phenomenon has been attributed to a delay in activating attentional or motor processes to a previously cued stimulus. Two experiments required subjects to localize or identify a target stimulus. In Experiment 1, the subjects’ eyes were not monitored. In Experiment 2, the subjects’ eyes were monitored, and the subjects were instructed to either execute or withhold an eye movement to a target stimulus. The results indicated that IOR was always present for location and identification responses, supporting an attentional account of IOR. However, IOR was larger when eye movements were executed, indicating that a motor component can contribute to IOR. Finally, when eye movements were withheld, IOR was larger when a target was presented alone than when it was presented with a distractor, suggesting that IOR is larger for exogenous than for endogenous covert orienting. Together, the data indicate that IOR is composed of both an oculomotor component and an attentional component.