A new estimation of the duration of attentional dwell time

How rapidly can attention move from one object to the next? Previous studies in which the dwell time paradigm was used have estimated attentional switch times of 200–500 msec, results incompatible with the search rate estimates of 25–50 msec shown in numerous visual search studies. It has been argued that dwell times are so long in the dwell time paradigm because the attentional shifts measured are unlike those used in visual search. In the present experiment, a variation of a visual search task was used, in which serial endogenous (volitional) deployments of attention were measured directly by means of a probe reaction time task. The experiment revealed a dwell time of about 250 msec, consistent with the faster estimates from other dwell time studies. This result suggests that endogenous shifts of attention may be relatively slow and that the faster attentional shifts estimated from visual search tasks may be due to the involvement of bottom-up processes.     

The speed of free will

Do voluntary and task-driven shifts of attention have the same time course? In order to measure the time needed to voluntarily shift attention, we devised several novel visual search tasks that elicited multiple sequential attentional shifts. Participants could only respond correctly if they attended to the right place at the right time. In control conditions, search tasks were similar but participants were not required to shift attention in any order. Across five experiments, voluntary shifts of attention required 200–300 ms. Control conditions yielded estimates of 35–100 ms for task-driven shifts. We suggest that the slower speed of voluntary shifts reflects the “clock speed of free will”. Wishing to attend to something takes more time than shifting attention in response to sensory input.     

Involuntary attentional shifts due to orientation differences

We tested the ability of orientation differences to cause involuntary shifts of visual attention and found that these attentional shifts can occur in response to an orientation “pop-out” display. Texturelike cue stimuli consisting of discrete oriented bars, with either uniform orientation or containing a noninformative orthogonally oriented bar, were presented for a variable duration. Subsequent to or partially coincident with the cue stimulus was the target display of a localization or two-interval forced-choice task, followed by a mask display. Naive subjects consistently showed greater accuracy in trials with the target at the location of the orthogonal orientation compared with trials with uniformly oriented bars, with only 100 msec between the cue and mask onsets. Discriminating these orientations required a stimulus onset asynchrony (SOA) of 50–70 msec. The attentional facilitation is transient, in most cases absent, with a cue-mask SOA of 250 msec. These results suggest that the preattentive character of some texture discrimination tasks with SOAs of only 100 msec is vitiated by the involuntary attentional shifts that are caused by orientation differences.     

Time course of visual attention across perceptual levels and objects

Theories of shifts of visual attention based on attentional blink or dwell time do not directly address shifts of attention across different levels (global or local) involving multiple objects. Two experiments were conducted employing the attentional dwell time paradigm to investigate the shifts of visual attention between objects selected at same or different levels. Participants were instructed to identify two successive compound stimuli at a pre-specified level (global or local) presented at two different locations with variable SOA. The initial pair of locations in which the stimulus was presented was fixed in Experiment 1 but not in Experiment 2. Experiment 1 results showed very little impairment for second target identification when both the targets were at the global level. Attentional shift was better with both targets at the same level compared to different levels. Experiment 2 results showed that local followed by global target identification is difficult at short SOAs compared to other conditions. The results indicate that scope of attention affects the time course of visual attention. Global processing could be performed with very little capacity limitation simultaneously with distributed attention. The default mode of attention might be distributed and attention becomes focused for target identification. Different mechanisms may underlie shifts in focused attention between different locations and changes in attentional set required by changes in perceptual levels.     

Distinguishing between the precision of attentional localization and attentional resolution

Attentional resolution is a construct that refers to the minimal separation that allows one stimulus to be attended separately from nearby stimuli. The attentional walk task, which requires a series of covert shifts of attention within variably dense arrays of stimuli, was introduced as a method of measuring attentional resolution. Using a cuing task, we show that individual items within arrays that are too dense to support an attentional walk can nonetheless be attended. We note that the precision with which attention can be localized is, in principle, a limitation separate from attentional resolution and conclude that performance in the attentional walk task is better suited for measuring this limitation than for measuring attentional resolution per se.     

The time course of attentional zooming: A comparison of voluntary and involuntary allocation of attention to the levels of compound stimuli

Summary The time course of attentional zooming between the levels of hierarchically structured compound stimuli (level-specific covert orienting of attention) is explored experimentally. The experiment compares the RTSOA functions of voluntarily and involuntarily initiated level-specific reorienting within a cost-benefit experiment using level-specific cues. With respect to the two modes of initiation, the results reveal no functional differences between attention shift and attentional zooming. Both can be initiated either voluntarily or involuntarily, the latter mode dominating the former; for both, involuntary initiation produces faster reorienting of attention than does voluntary initiation, and for both, involuntary initiation is more effective than voluntary initiation. However, the time needed to complete attentional orienting is about twice as long for zooming than for shifts. This quantitative difference suggests that there is a functional difference between level-specific and horizontal covert orienting. The difference is explained by postulating that zooming and attention shifts differ in the number of parameter sets that have to be adjusted in the reorienting of attention. The experiment also reveals that attentional zooming to the local level needs more time than does zooming to the global level. This result gives some support to the hypothesis that the RT difference between global and local identifications (Navon's global-dominance phenomenon) is due to an additional step in the course of reorienting attention away from the global level (which is usually attended to first) to the local level, when this level is to be identified.     

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.     

The time course of intended and unintended allocation of attention

According to the contingent involuntary orienting hypothesis, only stimuli that match the attentional control settings based on intentions capture attention. In contrast, the surprise-capture hypothesis states that expectancy-discrepant stimuli can capture attention even if they do not match the control settings, implying unintended capture. The purpose of this study is to investigate whether unintended and intended attentional shifts are characterized by different time courses, indicating different underlying mechanisms. An unintended attentional shift was tested by the first, unannounced presentation of a color singleton at the location of a visual search target, and intended shifts by the following repeated presentations of a predictive singleton. Differences in time course were revealed by varying the stimulus onset asynchrony (SOA) between singleton and target. Results showed that accuracy with expected singletons was barely affected by SOA, whereas SOA strongly affected accuracy with the unexpected singleton. The results are interpreted as supporting the surprise-capture hypothesis. It is furthermore argued that a division of labor between contingent capture and surprise in the control of attention supports adaptive behavior.     

Objects but not concepts modulate the size of the attended region

Here we investigated the types of stimuli that modulate the size of the attentional spotlight. In particular, it has been previously shown that conceptual cues that either directly refer to or are semantically related to particular spatial locations can shift attention to that location (known as “conceptual cueing”). For example, reading the word sun or joy can shift attention upward whereas the word boot or hostile can shift attention downward. Here, therefore, we tested whether words could modulate the size of the attended area. Across five experiments, we found that words that either directly referred to, or were abstractly associated with, particular sizes (small versus large) did not change the size of the attentional spotlight, whereas the presence of differently sized stimuli did, as evidenced by faster responses to targets when the spotlight is small than when it is large. This suggests that physical but not conceptual inducers can modulate the size of the attentional spotlight. This highlights an important difference between the regulation of spotlight size and shifts of attention, supporting the notion that they are subserved by distinct mechanisms.     

Attention and saccadic eye movements

Four threshold detection experiments addressed three issues concerning the relationship between movements of spatial attention and saccadic eye movements: (a) the time course of attention shifts wit saccades, (b) the response of the two systems to changes in stimulus parameters, and (c) the relationship of attention to saccadic suppression. These issues bear on the more general question of the degree of independence between the saccadic and attentional movement systems. The results of these experiments support the contention that the mechanisms that shift attention are separate from those that control saccadic eye movements. Relevant events in the visual field periphery, however, will trigger both a saccade and attention shift. The attentional response to such events does not appear to be under subjects' control. The implication of these results for theories of saccadic suppression is discussed.     

Self-referential schemas and attentional bias predict severity and naturalistic course of depression symptoms

Attentional bias and self-referential schemas have been observed in numerous cross-sectional studies of depressed adults and are theorised to maintain negative mood. However, few longitudinal studies have examined whether maladaptive cognition predicts the course of depressive symptoms. Fifty-seven adults with elevated depression symptoms were assessed for negative attentional bias using a dot-probe task with eye-tracking and self-referential schemas using a self-referent encoding task. Participants subsequently completed five weekly depression symptom assessments. Participants with more negative self-referential schemas had higher baseline depression symptoms (r?=?.55). However, participants who spent more time attending to negative words showed greater symptom worsening over time (r?=?.42). The findings for negative self-referential schemas replicate past research, while the findings for negative attention bias represent the first evidence showing that attentional biases predict naturalistic symptom course. This work suggests that negative attention biases maintain depression symptoms and represent an important treatment target for neurocognitive therapeutics.     

Stress in telephone helpline nurses is associated with failures of concentration,attention and memory,and with more conservative referral decisions

Nurses working for telephone‐based medical helplines must maintain attentional focus while quickly and accurately processing information given by callers to make safe and appropriate treatment decisions. In this study, both higher levels of general occupational stress and elevated stress levels on particular shifts were associated with more frequent failures of attention, memory, and concentration in telephone nurses. Exposure to a stressful shift was also associated with a measurable increase in objectively assessed information‐processing errors. Nurses who experienced more frequent cognitive failures at work made more conservative decisions, tending to refer patients on to other health professionals more often than other nurses. As stress is associated with cognitive performance decrements in telephone nursing, stress‐reduction interventions could improve the quality and safety of care that callers to medical helplines receive.     

Attentional strategies and the visual control of discrete movements

The relationship between the availability of visual information and attention demands during the production of a discrete motor act was examined. Subjects were required to move a linear slide a distance of 15 cm in both 150 and 600 msec conditions under three light manipulations, viz., light always on; light always terminated as movement began; or, subject was unsure as to whether light would stay on or terminate. A simple key press by the index finger of the opposite hand to a tone was used as a secondary task and a measure of attention demands. The light manipulation influenced attention demands on the rapid 150 msec movement such that more attention was demanded when the subject knew the light would terminate. No such attentional strategy differences were found with the slow 600 msec movement. These findings suggest that task constraints in the form of kinematic criteria, together with the perceived availability of visual information, contribute to determining attentional strategy in movement production.     

Positive mood broadens visual attention to positive stimuli

In an attempt to investigate the impact of positive emotions on visual attention within the context of Fredrickson’s (1998) broaden-and-build model, eye tracking was used in two studies to measure visual attentional preferences of college students (n=58, n=26) to emotional pictures. Half of each sample experienced induced positive mood immediately before viewing slides of three similarly-valenced images, in varying central-peripheral arrays. Attentional breadth was determined by measuring the percentage viewing time to peripheral images as well as by the number of visual saccades participants made per slide. Consistent with Fredrickson’s theory, the first study showed that individuals induced into positive mood fixated more on peripheral stimuli than did control participants; however, this only held true for highly-valenced positive stimuli. Participants under induced positive mood also made more frequent saccades for slides of neutral and positive valence. A second study showed that these effects were not simply due to differences in emotional arousal between stimuli. Selective attentional broadening to positive stimuli may act both to facilitate later building of resources as well as to maintain current positive affective states.     

Aging and mechanisms of visual selective attention: Effects on word localization and identification

Abstract

The present study investigated age differences in attentional allocation in a word localization and identification task. Response times for valid and invalid spatial cue conditions were compared for each of two age groups under two SOA conditions: 500 msec and 1000 msec. Very high benefits for valid cues in terms of response time were found for both groups. Results indicated that attention was more important for words when compared with similar earlier studies using a simple shape identification task. A sensitive model-fitting technique was used to compare the cost and benefit of selective attention to words; it revealed that attention can be concentrated away from the fovea to benefit in word identification in much the same way for both age groups. The model-fit analysis also revealed that attention for word identification, and perhaps any more complex visual stimuli, is more diffuse than for simple shape identification. In addition, older adults are more likely to avoid the foveal area in order to distribute attentional resources to the periphery and are able to increase these effects of selection at the longer SOA. This suggests that older adults are using attention to offset visual processing deficits for peripheral information such as letter information in the reading process. The results support a two-process view of attention where attention consists both of selection and inhibition and provide evidence to support a theory of reduced inhibitory processeses as a cause for cognitive slowing associated with aging.     

A re-examination of the impact of object processing on shifts of spatial attention

When two targets are presented in rapid succession at the same spatial location, processing of the first is highly efficient, while processing of the second is often profoundly impaired at brief inter-target intervals (attentional blink; AB). While the AB has been shown to impact many processes, it is still unclear whether this includes the ability to shift spatial attention. The present study examined this question using a more sensitive dependent measure than past studies; namely, response times. It also evaluated whether masking of the cue stimulus modulated the effect of the AB on spatial shifts. The results showed significant cueing effects on T2 response times that were strongly modulated by the AB. This supports suggested links between mechanisms underlying object processing and spatial shifts of attention.     

Attention, researchers! it is time to take a look at the real world

Theories of attention, too often generated from artificial laboratory experiments, may have limited validity when attention in the natural world is considered. For instance, for more than two decades, conceptualizations of "reflexive" and "volitional" shifts of spatial attention have been grounded in methodologies that do not recognize or utilize the basic fact that people routinely use the eyes of other people as rich and complex attentional cues. This fact was confirmed by our novel discovery that eyes will trigger a reflexive shift of attention even when they are presented centrally and are known to be spatially nonpredictive. This exploration of real-world attention also led to our finding that, contrary to popular wisdom, arrows, like eyes, are capable of producing reflexive shifts of attention—a discovery that brings into question much of the existing attention research. We argue that research needs to be grounded in the real world and not in experimental paradigms. It is time for cognitive psychology to reaffirm the difficult task of studying attention in a manner that has relevance to real-life situations.     

Attentional shift by eye gaze requires joint attention: Eye gaze cues are unique to shift attention1

Researchers have demonstrated that attentional shift triggered by gaze direction is reflexive. However, here we show that attentional shift by gaze direction was not always reflexive, but could be modulated by another's perspective. In Experiment 1, a schematic face's line of sight to a peripheral target was obstructed by a vertical barrier located between the face and the target under two conditions. However, the line of sight of the face was clear under another two conditions, in which the barrier was located behind the line of sight by utilizing a depth cue. The gaze cue shifted attention only when the line of sight was not blocked (i.e. joint attention was attained). The arrow cue did not shift attention regardless of the obstruction conditions in Experiment 2. These results suggest that attentional shift by gaze cues, but not arrow cues, involve a higher social cognitive process such as interpretation of the gaze.     

Focal distraction: spatial shifts of attentional focus are not required for contingent capture

Contingent capture occurs when distractors that share the target's defining attribute capture attention and slow down target identification. This slowdown has been attributed to an involuntary attentional shift to the location of a pertinent distractor. The present study examined an additional source of delay: the time spent in processing pertinent distractors. In 7 experiments, distractors were presented at fixation, and targets were presented either at fixation or peripherally. Contingent capture invariably occurred when a salient distractor was presented within about 600 ms before the target, even when spatial shifts in attentional focus were ruled out. A 2-stage model is proposed in which stimuli must pass an input filter tuned to the target's defining attribute before gaining access to a high-level stage that is unavailable while a distractor is being processed.     

Sex Differences in Certain Mental Disorders Among Whites and Negroes in Georgia During the Decade 1923-1932

In two three-interval temporal forced-choice experiments eight subjects were tested to determine the effect of a cue on the rate of detection of a signal when both cue and detection stimulus were of very brief duration and were separated by randomly varied temporal intervals (delta ts). Delta ts ranged from a cue precedence of 900 msec, through simultaneous presentation, to a detection-stimulus precedence of 900 msec.

A significant quadratic trend was found in the delta-t variable, with maximum detection when cue and detection stimulus were simultaneous, and there was an indication that the quadratic trend differed between the two stimulus combinations. An attempt was made to distinguish between attentional effects linked to the time of occurrence of the cue and attentional effects linked to the time of occurrence of the detection stimulus.