The spatial extent of focused attention modulates attentional disengagement.

Attention can be flexibly changed to optimize visual processing: it can be oriented, resized, or even divided. Although much is known about these processes individually, much less is known about how they interact with one another. In the present study we examined how the spatial extent of the attentional focus modulates the efficiency of the first component of attentional orienting, the disengagement of attention. To this end, we used abrupt-onset stimuli of different sizes to trigger the reflexive resizing of the attentional focus (Castiello and Umiltà in Acta Psychol 73:195-209, 1990), combined with a gap task to assess the efficiency of attentional disengagement (Mackeben and Nakayama in Vis Res 33:85-90, 1993). The results of five experiments showed that the magnitude of the gap effect is significantly greater when the scope of attention is small than when it is large, indicating that disengaging attention is delayed when attention is highly focused. Furthermore, these findings highlight that different aspects of attentional control interact with one another, emphasizing the importance of studying them in conjunction.

What factors influence the switch from unitary to divided attention?

The focus of attention can be either unitary or divided and can transition from unitary to divided while performing a task. In Experiment 1, we investigated whether alerting hastens the transition from unitary to divided attention. To this end, we employed a dual-RSVP-stream Attentional Blink task (AB; impaired perception of the second of two rapidly sequential targets) with two pairs of letter targets (T1-pair and T2-pair). One component of the AB known as Lag-1 sparing (unimpaired perception of the T2-pair when it is presented directly after the T1-pair) occurs only when the T2-pair falls in an attended location. When the T2-pair falls in an unattended location, the converse pattern occurs (Lag-1 deficit). Accordingly, we used the incidence of Lag-1 sparing/deficit to index whether a location was attended or unattended. We found that presenting a brief brightening flash of the screen (alerting) just before the T1-pair hastened the transition from the initial unitary focus to a divided focus. In Experiment 2, we pitted the hastening account against an alternative hypothesis that the flash triggers phasic activation of the Locus Coeruleus-norepinephrine neuromodulatory system, thus resetting the underlying neural networks that mediate the distribution of attention, triggering a switch from unitary to divided attention. The results of Experiment 2 were incompatible with the hastening account, but consistent with the network-reset account.

Attention scaling modulates the effective capacity of visual sensory memory.

Visual sensory memory (VSM) has a high capacity, but its contents are fleeting. Recent evidence that the breadth of attention strongly influences the efficiency of visual processing suggests that it might also modulate the effective capacity of VSM. We manipulated the breadth of attention with different cue sizes and used the partial-report technique to estimate the capacity of VSM. Whether attention was deployed voluntarily or captured by a salient cue, narrowly focused attention increased the effective capacity of VSM. This study reveals, for the first time, a direct influence of the breadth of attention on the effective capacity of VSM.

Sudden Events Change Old Visual Objects Into New Ones: A Possible Role for Phasic Activation of Locus Coeruleus.

We report a novel visual phenomenon called the rejuvenation effect. It causes an "old" object that has been on view for some time to acquire the properties of a suddenly appearing new object. In each experiment, a square outline was displayed continuously on one side of fixation. The target (an asterisk) was presented either inside the square or on the opposite side of fixation. On half of the trials, a transient visual or auditory event preceded the target. In Experiment 1a ( N = 139), response times were faster when the target appeared inside the square, but only when it was preceded by a transient event, consistent with the network-reset theory of locus coeruleus-norepinephrine (LC-NE) phasic activation. Three further experiments confirmed the predictions of network-reset theory, including the absence of rejuvenation in participants with atypical LC-NE functioning (individuals with symptoms of autism spectrum disorder). These findings provide new perspectives on what causes a visual object to be perceived as new.

First unitary, then divided: the temporal dynamics of dividing attention.

Whether focused visual attention can be divided has been the topic of much investigation, and there is a compelling body of evidence showing that, at least under certain conditions, attention can be divided and deployed as two independent foci. Three experiments were conducted to examine whether attention can be deployed in divided form from the outset, or whether it is first deployed as a unitary focus before being divided. To test this, we adapted the methodology of Jefferies, Enns, and Di Lollo (Journal of Experimental Psychology: Human Perception and Performance 40: 465, 2014), who used a dual-stream Attentional Blink paradigm and two letter-pair targets. One aspect of the AB, Lag-1 sparing, has been shown to occur only if the second target pair appears within the focus of attention. By presenting the second target pair at various spatial locations and assessing the magnitude of Lag-1 sparing, we probed the spatial distribution of attention. By systematically manipulating the stimulus-onset-asynchrony between the targets, we also tracked changes to the spatial distribution of attention over time. The results showed that even under conditions which encourage the division of attention, the attentional focus is first deployed in unitary form before being divided. It is then maintained in divided form only briefly before settling on a single location.

The exogenous and endogenous control of attentional focusing.

Selective visual attention involves prioritizing both the location (orienting) and distribution (focusing) of processing. To date, much more research has examined attentional orienting than focusing. One of the most well-established findings is that orienting can be exogenous, as when a unique change in luminance draws attention to a spatial location (e.g., Theeuwes in Atten Percept Psychophys 51:599-606, 1992; Yantis and Jonides in J Exp Psychol Hum Percept Perform 10:601, 1984), and endogenous, as when a red distractor shape diverts attention when one is looking for a red target (e.g., Bacon and Egeth in Percept Psychophys 55:485-496, 1994; Folk et al. in J Exp Psychol Hum Percept Perform 18:1030, 1992). Here we ask whether attentional focusing-the broadening and contracting of prioritized processing-is influenced by the same two factors. Our methodology involved a dual-stream attentional blink task; participants monitored two spatially separated streams of items for two targets that could appear unpredictably either in the same stream or in opposite streams. The spatial distribution of attention was assessed by examining second-target accuracy in relation to inter-target lag and target location (same or opposite streams). In Experiment 1, we found that attentional contracting was more rapid when the targets differed in luminance from the distractor items. In Experiments 2 and 3, we found that the rate of attentional contracting was slower when there were task-relevant distractors in the stream opposite the first target. These results indicate that the rate of attentional focusing, like orienting, can be modulated by both exogenous and endogenous mechanisms.

On the time course of attentional focusing in older adults.

Many sensory and cognitive changes accompany normal ageing, including changes to visual attention. Several studies have investigated age-related changes in the control of attention to specific locations (spatial orienting), but it is unknown whether control over the distribution or breadth of attention (spatial focus) also changes with age. In the present study, we employed a dual-stream attentional blink task and assessed changes to the spatial distribution of attention through the joint consequences of temporal lag and spatial separation on second-target accuracy. Experiment 1 compared the rate at which attention narrows in younger (mean age 22.6, SD 4.25) and older (mean age 66.8, SD 4.36) adults. The results showed that whereas young adults can narrow attention to one stream within 133 ms, older adults were unable to do the same within this time period. Experiment 2 showed that older adults can narrow their attention to one stream when given more time (266 ms). Experiment 3 confirmed that age-related changes in retinal illuminance did not account for delayed attentional narrowing in older adults. Considered together, these experiments demonstrate that older adults can narrow their attentional focus, but that they are delayed in initiating this process compared to younger adults. This finding adds to previously reported reductions in attentional dynamics, deficits in inhibitory processes, and reductions in posterior parietal cortex function that accompany normal ageing.

Linear changes in the spatial extent of the focus of attention across time.

This research examined changes in the spatial extent of focal attention over time. The Attentional Blink (impaired perception of the second of two targets) and Lag-1 sparing (the seemingly paradoxical finding that second-target accuracy is high when the second target immediately follows the first) were employed in a dual-stream paradigm to index spatiotemporal changes in focal attention. Lag-1 sparing occurs to targets in different streams if the second target falls within the focus of attention. Focal attention is assumed to initially encompass both streams but to shrink rapidly to the first-target stream, thus withdrawing from the second target if it appears in the opposite stream. The time available for the focus to shrink before second target onset was manipulated by varying the stimulus-onset asynchrony (SOA) between successive items in the stream. There was a progressive transition from Lag-1 sparing to its converse (Lag-1 deficit) as the SOA was increased. This transition was related linearly to SOA, which suggests that the spatial extent of focal attention varies linearly over time.

Deployment of spatial attention to a structural framework: exogenous (alerting) and endogenous (goal-directed) factors.

The main question examined in the present work was whether spatial attention can be deployed to an appropriate structural framework not only endogenously when the framework is displayed continuously, as in previous work, but also exogenously, when it is displayed transiently 100 ms before the target. The results of five experiments answered that question in the negative. We found that the onset transient triggered by a brief presentation of the structural framework did enhance the response to the upcoming target. That enhancement, however, was due not to the framework itself but to the alerting effect produced by its sudden onset, witness the finding that the same enhancement was produced by an onset transient triggered by a featureless stimulus (i.e., by a brief dimming of the entire screen, in the absence of a structural framework). We conclude that spatial attention can be deployed to the region demarcated by a structural framework when it is deployed endogenously but not when it is deployed exogenously. A theoretical account of the results is proposed in terms of the temporal dynamics of the locus cœruleus/norepinephrine neuromodulatory system.

Inhibition of return to an occluded object depends on expectation.

Inhibition of return (IOR) is indexed by slower reaction times to targets presented at previously attended locations or objects. If a moving object is occluded, some studies find IOR, others do not. Four experiments examined whether this inconsistency hinges on the observer's expectation as to whether the object continues to exist at the end of its motion sequence. Results showed that observer expectation is a powerful determining factor: IOR occurs only if the observer expects the object to continue to exist. In contrast, if the object is not occluded, IOR occurs only if the object remains on view immediately before the target is presented. It was concluded that 2 factors, object continuity and observer expectation, mediate both location- and object-based IOR.

When can spatial attention be deployed in the form of an annulus?

Can spatial attention be deployed as an annulus? Some studies have answered this question in the positive, others in the negative. We tested the hypothesis that annular deployment depends on the presence of a suitable structural framework to which attention can be anchored. To this end, we added a structural framework to the displays of a study that failed to find an annular distribution of attention. The targets were displayed in an annular region around a central stream of task-irrelevant distractors which captured attention and impaired target identification. This design was replicated in our No-Anchors condition. In the Anchors condition in Experiments 1 and 2, a square outline was displayed at each of the four possible target locations. Consistent with the idea that attention can be deployed as an annulus only when a visual framework is present, the targets were identified more accurately (Experiment 1) and more rapidly (Experiment 2) when anchors were present than when they were absent. The number of anchors was increased to eight in Experiment 3. In Experiment 4 the central stream was omitted to verify that the enhanced performance did not arise from intrinsic properties of the anchors themselves. In Experiment 5, targets were presented in a blank annular region delimited by two concentric circles, thus obviating the possibility that attention was deployed as four or eight separate foci in Experiments 2 and 3, respectively.

Attending to illusory differences in object size.

Focused visual attention can be shifted between objects and locations (attentional orienting) or expanded and contracted in spatial extent (attentional focusing). Although orienting and focusing both modulate visual processing, they have been shown to be distinct, independent modes of attentional control. Objects play a central role in visual attention, and it is known that high-level object representations guide attentional orienting. It not known, however, whether attentional focusing is driven by low-level object representations (which code object size in terms of retinotopic extent) or by high-level representations (which code perceived size). We manipulated the perceived size of physically identical objects by using line drawings or photographs that induced the Ponzo illusion, in a task requiring the detection of a target within these objects. The distribution of attention was determined by the perceived size and not by the retinotopic size of an attended object, indicating that attentional focusing is guided by high-level object representations.

The flexible focus: whether spatial attention is unitary or divided depends on observer goals.

The distribution of visual attention has been the topic of much investigation, and various theories have posited that attention is allocated either as a single unitary focus or as multiple independent foci. In the present experiment, we demonstrate that attention can be flexibly deployed as either a unitary or a divided focus in the same experimental task, depending on the observer's goals. To assess the distribution of attention, we used a dual-stream Attentional Blink (AB) paradigm and 2 target pairs. One component of the AB, Lag-1 sparing, occurs only if the second target pair appears within the focus of attention. By varying whether the first-target-pair could be expected in a predictable location (always in-stream) or not (unpredictably in-stream or between-streams), observers were encouraged to deploy a divided or a unitary focus, respectively. When the second-target-pair appeared between the streams, Lag-1 sparing occurred for the Unpredictable group (consistent with a unitary focus) but not for the Predictable group (consistent with a divided focus). Thus, diametrically different outcomes occurred for physically identical displays, depending on the expectations of the observer about where spatial attention would be required.

Emotional valence and arousal interact in attentional control.

A recent study demonstrated that observers' ability to identify targets in a rapid visual sequence was enhanced when they simultaneously listened to happy music. In the study reported here, we examined how the emotion-attention relationship is influenced by changes in both mood valence (negative vs. positive) and arousal (low vs. high). We used a standard induction procedure to generate calm, happy, sad, and anxious moods in participants. Results for an attentional blink task showed no differences in first-target accuracy, but second-target accuracy was highest for participants with low arousal and negative affect (sad), lowest for those with strong arousal and negative affect (anxious), and intermediate for those with positive affect regardless of their arousal (calm, happy). We discuss implications of this valence-arousal interaction for the control of visual attention.

Ignorance is bliss: the role of observer expectation in dynamic spatial tuning of the attentional focus.

When two sequential targets (T1, T2) are inserted in an RSVP stream of distractors, perception of T2 is impaired at intertarget lags shorter than 700 msec. Paradoxically, this deficit disappears when T2 is presented directly after T1 (lag-1 sparing). Visser, Bischof, and Di Lollo (1999) found that lag-1 sparing occurs only when T1 and T2 are presented in the same stream. In contrast, Shih (2000) obtained lag-1 sparing with targets insepa-rate streams. Four experiments addressed this inconsistency and revealed lag-1 sparing with targets in different streams, but only when observers had no foreknowledge of T1's location. We hypothesized that when T1 location is known, attention is focused narrowly on that stream; if T2 then appears in the other stream it is missed, and lag-1 sparing does not occur. When T1 location is not known, attention is focused broadly, encompassing both streams, and lag-1 sparing ensues.