Modulation of object-based attention by spatial focus under endogenous and exogenous orienting.

In R. Egly, J. Driver, and R. D. Rafal's (1994) influential double-rectangle spatial-cuing paradigm, exogenous cues consistently induce object-based attention, whereas endogenous cues generally induce space-based attention. This difference suggests an interdependency between mode of orienting (endogenous vs exogenous) and mode of selection (object based vs space based). However, mode of orienting is generally confounded with initial focus of attention: Endogenous orienting begins with attention focused on a central cue, whereas exogenous orienting begins with attention widely spread. In this study, an attentional-focusing hypothesis is examined and supported by experiments showing that for both endogenous and exogenous cuing, object-based effects are obtained under conditions that encourage spread attention, but they are attenuated under conditions that encourage focused attention. General implications for object-based attention are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Orienting attention without awareness

Previous research has shown that visual attention can be directed to a spatial location in 2 qualitatively different ways. Attention can be allocated endogenously in response to centrally presented precues, or it can be captured exogenously by a visual stimulus with an abrupt onset. It has been suggested that exogenous orienting of attention is an automatic process, whereas endogenous orienting of attention represents a controlled and strategic process. M.I. Posner and C.R.R. Snyder (1975) suggested that an automatic process occurs without intention, does not interfere with other mental processes, and does not necessarily give rise to awareness, whereas a controlled process will likely interfere with other processes and necessarily requires intention and awareness. Three experiments investigated the role of awareness in orienting visual attention. Endogenous and exogenous components of orienting attention were placed in opposition to each other to assess the automaticity of exogenous orienting by examining the potential for brief stimulus events to capture attention in the absence of subjective awareness. Results show that an exogenous cue presented below a subjective threshold of awareness captured attention automatically and without awareness.     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Competition Between Endogenous and Exogenous Orienting of Visual Attention.

The relation between reflexive and voluntary orienting of visual attention was investigated with 4 experiments: a simple detection task, a localization task, a saccade toward the target task, and a target identification task in which discrimination difficulty was manipulated. Endogenous and exogenous orienting cues were presented in each trial and their validity was manipulated orthogonally to examine whether attention mechanisms are mediated by separate systems and whether they have additive and independent effects on visual detection and discrimination. The results showed that each orienting mechanism developed its typical and independent effect in every case except for the difficult identification task. A theoretical framework for understanding the relationship between endogenous and exogenous orienting of attention is proposed, tested, and confirmed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory processes in covert orienting in patients with Alzheimer's disease

Previous studies of covert orienting in Alzheimer's disease (AD) have investigated exogenous and endogenous processes separately. We aimed to investigate how the 2 modes of orienting interact to control attention in healthy older participants and patients with AD. The covert orienting of visual attention task (COVAT) with abrupt onset cues was used in all experiments. In Experiments 1 and 2, predictive information was added to cues to initiate an endogenous orienting response. Results showed that healthy older participants were able to use endogenous processes to inhibit exogenous orienting. In contrast, patients with AD were unable to inhibit exogenous orienting to cues even when targets rarely appeared there. Experiment 3 investigated inhibition of return (IOR) in patients with AD. Both healthy older controls and patients with AD showed a normal IOR, suggesting that exogenous orienting processes are relatively unaffected by the normal aging process or in patients with AD. A model of covert orienting in which exogenous and endogenous orienting processes interact to control attentional behaviors is discussed.     

Saccade preparation inhibits reorienting to recently attended locations.

We measured manual reaction time in normal human Ss to confirm that an eccentric visual signal has a biphasic effect on covert attention and eye movements. First, it summons attention and biases a saccade toward the signal; a subsequent inhibition of return then slows responses to signals at that location. A temporal hemifield dominance for inhibition of return was shown; this finding coverges with observations (M. I. Posner et al; see record 1986-22316-001) in neurologic patients to suggest that it is mediated by midbrain pathways. Endogenous orienting of attention, from a central arrow cue, did not activate inhibition of return, whereas endogenous saccade preparation did so as effectively as an exogenous signal, even when no saccade was made. Inhibition of return is activated by midbrain oculomotor pathways and may function as a location "tagging" mechanism to optimize efficiency of visual search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrophysiological evidence for the "missing link" in crossmodal attention.

Notes that orienting attention involuntarily to the location of a sensory event influences responses to subsequent stimuli that appear in different modalities with one possible exception; orienting attention involuntarily to a sudden light sometimes fails to affect responses to subsequent sounds (e.g., C. Spence and J. Driver, 1997). Here the authors investigated the effects of involuntary attention to a brief flash on the processing of subsequent sounds in a design that eliminates stimulus–response compatibility effects and criterion shifts as confounding factors. 13 18–31 yr olds participated in the study. In addition, the neural processes mediating crossmodal attention were studied by recording event-related brain potentials. The data show that orienting attention to the location of a spatially nonpredictive visual cue modulates behavioral and neural responses to subsequent auditory targets when the stimulus onset asynchrony is short (between 100 and 300 ms). These findings are consistent with the hypothesis that involuntary shifts of attention are controlled by supramodal brain mechanisms rather than by modality-specific ones. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhanced facilitation of spatial attention in schizophrenia.

Objective: While attentional functions are usually found to be impaired in schizophrenia, a review of the literature on the orienting of spatial attention in schizophrenia suggested that voluntary attentional orienting in response to a valid cue might be paradoxically enhanced. We tested this hypothesis with orienting tasks involving the cued detection of a laterally presented target stimulus. Method: Subjects were chronic schizophrenia patients (SZ) and matched healthy control subjects (HC). In Experiment 1 (15 SZ, 16 HC), cues were endogenous (arrows) and could be valid (100% predictive) or neutral with respect to the subsequent target position. In Experiment 2 (16 SZ, 16 HC), subjects performed a standard orienting task with unpredictive exogenous cues (brightening of the target boxes). Results: In Experiment 1, SZ showed a larger attentional facilitation effect on reaction time than HC. In Experiment 2, no clear sign of enhanced attentional facilitation was found in SZ. Conclusions: The voluntary, facilitatory shifting of spatial attention may be relatively enhanced in individuals with schizophrenia in comparison to healthy individuals. This effect bears resemblance to other relative enhancements of information processing in schizophrenia such as saccade speed and semantic priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A unique role of endogenous visual-spatial attention in rapid processing of multiple targets.

Visual spatial attention can be exogenously captured by a salient stimulus or can be endogenously allocated by voluntary effort. Whether these two attention modes serve distinctive functions is debated, but for processing of single targets the literature suggests superiority of exogenous attention (it is faster acting and serves more functions). We report that endogenous attention uniquely contributes to processing of multiple targets. For speeded visual discrimination, response times are faster for multiple redundant targets than for single targets because of probability summation and/or signal integration. This redundancy gain was unaffected when attention was exogenously diverted from the targets but was completely eliminated when attention was endogenously diverted. This was not a result of weaker manipulation of exogenous attention because our exogenous and endogenous cues similarly affected overall response times. Thus, whereas exogenous attention is superior for processing single targets, endogenous attention plays a unique role in allocating resources crucial for rapid concurrent processing of multiple targets. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Competition between endogenous and exogenous attention to nonemotional stimuli in social anxiety.

This study investigated whether impaired endogenous attention and enhanced exogenous attention for the processing of nonemotional stimuli were observed in individuals with high social anxiety. In each trial, participants were presented with an endogenous cue at a center, followed by exogenous cues at peripheral locations; subsequently, nonemotional masked targets were presented wherein the subjects were asked to distinguish between the targets. The accuracy rates were influenced by social anxiety only in exogenous conditions. Individuals with high social anxiety exhibited higher accuracy in the valid condition than in the invalid condition of exogenous attention, whereas individuals with low social anxiety displayed uniform accuracy rates in valid, neutral, and invalid conditions. The validity effects in individuals with high social anxiety did not diminish when controlling for trait and state anxiety and depression. The results suggest that individuals with high social anxiety have an enhanced exogenous attentional system and that they are attracted to salient stimuli regardless of emotionality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recent developments in the study of tactile attention.

The last few years have seen a rapid growth of research on the topic of tactile attention. We review the evidence showing that attention can be directed to the tactile modality, or to the region of space where tactile stimuli are presented, in either an endogenous or exogenous (top-down or bottom-up) manner. We highlight the latest findings on the interaction between these two forms of attentional orienting in touch. We also review the latest research on tactile numerosity judgments and change detection highlighting the severe cognitive (attentional) limitations that constrain people's ability to process more complex tactile information displays. These findings are particularly important given that tactile interfaces are currently being developed for a number of different application domains. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Covert orienting of visuospatial attention in children with developmental coordination disorder

It is still unclear whether impairments in visuospatial processing in children with developmental coordination disorder (DCD) are a consequence of their motor deficits or are independent of them. In two experiments, 20 children with DCD and 20 matched controls were tested on the covert orienting of a visuospatial attention task (COVAT). Experiment 1 used a COVAT with peripheral cues and an 80% probability that targets would appear at the cued location. While the results suggested a deficit in the disengage operation of orienting covert attention for the DCD group, they were difficult to reconcile with models of covert orienting and the results of past research. Experiment 2 tested subjects on two new versions of the COVAT: the first used peripheral cues and no probability information (exogenous mode), and the second used central cues and an 80% probability that targets would appear at the cued location (endogenous mode). The DCD group displayed attentional orienting deficits only for the endogenous mode. These results suggest that impairments in the endogenous control of visuospatial attention are independent of motor deficits in DCD.     

On the uniqueness of attentional capture by uninformative gaze cues: Facilitation interacts with the Simon effect and is rarely followed by IOR.

Orienting to an uninformative peripheral cue is characterized by a brief facilitation followed by a long-lasting inhibition once attention is removed from the cued location. Although central gaze cues cause reflexive orienting, the inhibitory effect that is relatively ubiquitous following exogenous orienting to uninformative peripheral cues has been relatively rare. We hypothesized that IOR might be seen following gaze-induced orienting if attention were effectively returned to centre by a return gaze or return flash. The timecourse of gaze-directed orienting was measured by varying the interval between the gaze cue and a peripheral target requiring an orientation discrimination (permitting measurement of the Simon effect). Significant facilitation was observed at all but the longest SOA tested, 2,880 ms, by which time the facilitation had disappeared with no evidence of IOR. Gaze-induced cuing (which was unaffected by return cue condition) interacted with the Simon effect, decreasing it at the gazed-at location, a pattern that is not seen with more typical endogenous and exogenous cuing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visuospatial attention is guided by both the symbolic value and the spatial proximity of selected arrows.

There is considerable evidence that overlearned symbols, especially arrows, can orient attention to peripheral locations. In 2003, Pratt and Hommel showed that when 1 arrow is selected from a set of arrows, based on an attentional control setting for a specific target color, the selected arrow determines the orientation of attention. Recently, Leblanc and Jolicoeur (2010) reexamined this finding, and concluded that spatial proximity of the arrow to the target, not the symbolic value of the arrow, determines the orienting of attention. Here, we manipulated both the symbolic value of the cue (direction arrows or directionless circles) and the proximity of the cue to the peripheral target location (near or far), and found that although proximity does play a role in the orienting of attention (larger cuing effects were found with far cues than near cues), the symbolic content of the cue also plays an important role (larger cuing effects were found with arrows than circles). Thus, both the symbolic value and the spatial proximity of cues affect the orienting of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Audiovisual links in endogenous covert spatial attention.

In 7 experiments we investigated cross-modal links for endogenous covert spatial orienting in hearing and vision. Participants judged the elevation (up vs. down) of auditory or visual targets regardless of their laterality or modality. When participants were informed that targets were more likely on 1 side, elevation judgments were faster on that side, even if the modality of the target was uncertain. When participants expected a target on a particular side in Just 1 modality, corresponding shifts of covert attention also took place in the other modality, as evidenced by faster elevation judgments on that side. However, it was possible to "split" auditory and visual attention when targets in the 2 modalities were expected on constant but opposite sides throughout a block, although covert orienting effects were larger when targets were expected on the same side in both modalities. These results show that although endogenous covert attention does not operate exclusively within a supramodal system, there are strong spatial links between auditory and visual attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional effects of single dose triazolam

1. While the effects of benzodiazepines on human memory have been extensively studied little is known about the effects of these agents on attentional processes. The authors studied the effects of a single dose of triazolam on selective visual-spatial attention using a double blind, placebo controlled design. 2. In each of 2 sessions 12 normal volunteers ingested either 0.25 mg of triazolam or placebo. Attentional performance was evaluated using two versions of the covert orienting paradigm which measured automatic (exogenous) and controlled (endogenous) aspects of attentional orienting, respectively. 3. Triazolam selectively modified performance on automatic orienting to exogenous cues. Specifically, triazolam increased the facilitation of target detection seen at shorter (150 msec) SOA's. This may indicate an increase in facilitation and a reduction in inhibition or a slowing of the time course of the biphasic attentional effect normally resulting from exogenous cuing. 4. These results indicate the importance of using experimental paradigms which effectively dissociate endogenous and exogenous mechanisms of spatial orienting in studies evaluating the effects of pharmacological agents on visual-spatial attention.     

Separate mechanisms recruited by exogenous and endogenous spatial cues: Evidence from a spatial Stroop paradigm.

The present experiments tested whether endogenous and exogenous cues produce separate effects on target processing. In Experiment 1, participants discriminated whether an arrow presented left or right of fixation pointed to the left or right. For 1 group, the arrow was preceded by a peripheral noninformative cue. For the other group, the arrow was preceded by a central, symbolic, informative cue. The 2 types of cues modulated the spatial Stroop effect in opposite ways, with endogenous cues producing larger spatial Stroop effects for valid trials and exogenous cues producing smaller spatial Stroop effects for valid trials. In Experiments 2A and 2B, the influence of peripheral noninformative and peripheral informative cues on the spatial Stroop effect was directly compared. The spatial Stroop effect was smaller for valid than for invalid trials for both types of cues. These results point to a distinction between the influence of central and peripheral attentional cues on performance and are not consistent with a unitary view of endogenous and exogenous attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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 (1) when blocks contained a high proportion of central cues (Experiment 2) and (2) 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional bias to brief threat-related faces revealed by saccadic eye movements.

According to theories of emotion and attention, we are predisposed to orient rapidly toward threat. However, previous examination of attentional cueing by threat showed no enhanced capture at brief durations, a finding that may be related to the sensitivity of the manual response measure used. Here we investigated the time course of orienting attention toward fearful faces in the exogenous cueing task. Cue duration (20 ms or 100 ms) and response mode (saccadic or manual) were manipulated. In the saccade mode, both enhanced attentional capture and impaired disengagement from fearful faces were evident and limited to 20 ms, suggesting that saccadic cueing effects emerge rapidly and are short lived. In the manual mode, fearful faces impacted only upon the disengagement component of attention at 100 ms, suggesting that manual cueing effects emerge over longer periods of time. Importantly, saccades could reveal threat biases at brief cue durations consistent with current theories of emotion and attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic priming: A cognitive neuroscience approach.

Posner and Snyder have proposed that semantic priming involves two processes: Automatic spreading activation and consciously directed attention. According to this view, activation will spread from the node in memory for the prime to nodes for related words. This facilitates response to related words, but does not produce inhibitory effects. Attention, however, is viewed as a slow serial process that produces both facilitation and inhibition effects, but only at a long stimulus onset asynchrony (SOA). An alternative model has been developed based on a paper by Walley and Weiden. According to our model, facilitation effects are attributed to spreading activation in a network of neurons. Our model differs from Posner and Snyder's model in that we assume that automatic spreading activation, if strong enough to cause neurons to discharge, will produce inhibitory effects through a mechanism of recurrent lateral inhibition. Consequently, this model predicts that if spreading activation is strong enough, responding to unrelated target words will be inhibited even though attention is not directed to the related target. It is possible that even with strongly related prime-target pairs, spreading activation may not be sufficient to cause neurons to discharge and generate lateral inhibition without some additional facilitation resulting from effort-induced arousal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)