Exogenous visual attention prolongs perceived duration

Previous studies have shown that spatial attention prolongs the perceived duration of visual stimuli. Chen and O'Neill (Perception & Psychophysics, 63, 1229-1238, 2001) reported, however, the reversed result and thus challenged the generality of this attention effect. We therefore reinvestigated the influence of spatial attention on the perceived duration of visual stimuli in various experimental settings. In five experiments, perceived duration was longer for validly cued stimuli; thus, spatial attention was found to prolong perceived duration. In a further experiment, the specific conditions were such that neither the attention effect nor the reversed pattern, as found by Chen and O'Neill, emerged. Although we cannot provide a conclusive account of why Chen and O'Neill observed the reversed attention effect, the present results reinforce the generality of the spatial attention effect on perceived duration but also make advisable a systematic examination of the factors that might modulate this effect.     

Task-based working memory guidance of visual attention

Previous research has established that holding a stimulus in working memory (WM) facilitates the deployment of visual attention to that stimulus relative to other stimuli. The present study examined whether maintaining a specific task in WM would also bias the allocation of attention to the stimuli associated with that task. Participants performed a speeded letter search task while simultaneously keeping in WM one of two task cues shown at the beginning of each trial. The results showed that task-based WM guidance of attention was modulated by response latencies. Whereas the participants with fast reaction times showed little influence of WM contents, the participants with slow reaction times took longer to respond when the letter target appeared in a distractor stimulus consistent with the task cue held in mind. A subsequent Stroop experiment found a larger Stroop interference effect from the participants in the slow group compared with those in the fast group, suggesting that the differential WM effect between the two groups may be associated with an individual's ability to inhibit task-irrelevant information. Taken together, these results expanded the realm of previous research and provided further evidence for a close link between attention and WM.     

Sex differences in the duration of visual attention

Normal adult males and females looked at a series of photographs containing either a single adult male or female. Ss viewed each picture for as long as they wished. Assuming that measures of the duration of attention would reflect Ss attraction for the opposite sex, it was hypothesized that Ss would spend relatively more time viewing photographs of the opposite sex. The results failed to support the hypothesis. Although males did not differentially attend to the stimuli, females looked significantly longer at the females than they did at the males. The results were interpreted in terms of the “overt sexual content” of the stimuli and socially conditioned attentiveness and inattentiveness.     

Sex differences in the duration of visual attention

Normal adult males and females looked at a series of photographs containing either a single adult male or female. Ss viewed each picture for as long as they wished. Assuming that measures of the duration of attention would reflect Ss attraction for the opposite sex, it was hypothesized that Ss would spend relatively more time viewing photographs of the opposite sex. The results failed to support the hypothesis. Although males did not differentially attend to the stimuli, females looked significantly longer at the females than they did at the males. The results were interpreted in terms of the “overt sexual content” of the stimuli and socially conditioned attentiveness and inattentiveness.     

Automatic guidance of visual attention from verbal working memory

Previous studies have shown that visual attention can be captured by stimuli matching the contents of working memory (WM). Here, the authors assessed the nature of the representation that mediates the guidance of visual attention from WM. Observers were presented with either verbal or visual primes (to hold in memory, Experiment 1; to verbalize, Experiment 2; or merely to attend, Experiment 3) and subsequently were required to search for a target among different distractors, each embedded within a colored shape. In half of the trials, an object in the search array matched the prime, but this object never contained the target. Despite this, search was impaired relative to a neutral baseline in which the prime and search displays did not match. An interesting finding is that verbal primes were effective in generating the effects, and verbalization of visual primes elicited similar effects to those elicited when primes were held in WM. However, the effects were absent when primes were only attended. The data suggest that there is automatic encoding into WM when items are verbalized and that verbal as well as visual WM can guide visual attention.     

Object onset and parvocellular guidance of attentional allocation

The parvocellular visual pathway in the primate brain is known to be involved with the processing of color. However, a subject of debate is whether an abrupt change in color, conveyed via this pathway, is capable of automatically attracting attention. It has been shown that the appearance of new objects defined solely by color is indeed capable of modulating attention. However, given evidence suggesting that the visual system is particularly sensitive to new onsets, it is unclear to what extent such results reflect effects of color change per se, rather than effects of object onset. We assessed attentional capture by color change that occurred as a result of either new objects appearing or already-present "old" objects changing color. Results showed that although new object onsets accrued attention, changing the color of old objects did not. We conclude that abrupt color change per se is not sufficient to capture attention.     

Working memory and the guidance of visual attention: Consonance-driven orienting

Two experiments investigated the potential role of the content of working memory in guiding visual attention. Experiment 1 showed that maintaining a shape in working memory resulted in a decisive preference for moving attention to the same shape in the background when those shapes were task irrelevant. Experiment 2 showed a similar preference for words that were semantically related to an item held in working memory. We suggest that keeping an item active in working memory automatically results in a tendency for attention to be “attracted” to stimuli that are related to that item either visually or semantically.     

Working memory capacity and visual attention: top-down and bottom-up guidance

Previous studies have indicated that working memory capacity (WMC) is related to visual attention when selection of critical information must be made in the face of distraction. The present study examines whether WMC-related differences in flanker task performance might be decreased by displays that are designed to support bottom-up guidance of attention. Participants were required to respond to a centrally located target while ignoring a peripheral flanker. In one condition, bottom-up support was provided by embedding the target in a row of zeros. In another condition, the zeros were removed, thus emphasizing the role of top-down attention in selecting spatially defined information. It was found that the inclusion of zeros led to the elimination of WMC-related flanker effects. We conclude that bottom-up attentional guidance can attenuate the role of WMC in selective attention.     

Working memory capacity and visual attention: Top-down and bottom-up guidance

Previous studies have indicated that working memory capacity (WMC) is related to visual attention when selection of critical information must be made in the face of distraction. The present study examines whether WMC-related differences in flanker task performance might be decreased by displays that are designed to support bottom-up guidance of attention. Participants were required to respond to a centrally located target while ignoring a peripheral flanker. In one condition, bottom-up support was provided by embedding the target in a row of zeros. In another condition, the zeros were removed, thus emphasizing the role of top-down attention in selecting spatially defined information. It was found that the inclusion of zeros led to the elimination of WMC-related flanker effects. We conclude that bottom-up attentional guidance can attenuate the role of WMC in selective attention.     

Transient spatial attention and the perceived duration of brief visual events

This study was designed to explore the effects of transient attention—the stimulus-driven component of spatial attention—on the perceived duration of a brief visual event. Observers had to compare the duration of two disks presented successively within a single trial. The disks’ location and duration varied independently. One of these disks, the “attended disk”, was preceded by an attentional cue indicating the disk's location, attracting transient attention in advanced to the disk location. This attentional cue was either a typical onset cue (Experiments 1, 2, and 4) or a singleton cue (Experiment 3) that minimized the differences between the cues. The other disk, the “neutral disk”, was cued with a neutral cue that did not convey information regarding the disk location. We found that the attraction of transient attention to the location of the attended disk prolonged its perceived duration, but only when compared to brief nonattend stimuli.     

Flexible cue combination in the guidance of attention in visual search

Hodsoll and Humphreys (2001) have assessed the relative contributions of stimulus-driven and user-driven knowledge on linearly- and nonlinearly separable searches. However, the target feature used to determine linear separability in their task (i.e., target size) was required to locate the target. In the present work, we investigated the contributions of stimulus-driven and user-driven knowledge when a linearly- or a nonlinearly-separable feature is available but not required for target identification. We asked observers to complete a series of standard color × orientation conjunction searches in which target size was either linearly- or nonlinearly separable from the size of the distractors. When guidance by color × orientation and guidance by size information are both available, observers rely on whichever information results in the best search efficiency. This is the case irrespective of whether we provide target foreknowledge by blocking stimulus conditions, suggesting that feature information is used in both a stimulus-driven and a user-driven fashion.     

Effects of attention manipulation on judgments of duration and of intensity in the visual modality

The “attentional model” of time estimation assumes that temporal judgments depend on the amount of attention allocated to the temporal processor (the timer). One of the main predictions of this model is that an interval will be judged shorter when attention is not allocated to the temporal parameters of the task. Previous studies combining temporal and nontemporal tasks (dual-task method) have suggested that the time spent processing the target duration might be a key factor: The less time devoted by the subject to the temporal task, the shorter the judged duration. In the two experiments presented here, subjects were asked to judge both the duration of a visual stimulus and an increment in intensity occurring at any time during this stimulus. In the second experiment, trials without intensity increments were added. The main result is that the judged duration was shorter when the increment occurred later in the stimulus or did not occur. In those cases, subjects had been expecting increment occurrence during most part of the stimulus and thus had focused for a shorter time on stimulus duration. We propose that attention shifts related to expectancy and to detection of the increment reduce subjective duration.     

Orientation categories used in guidance of attention in visual search can differ in strength

We investigated orientation categories in the guidance of attention in visual search. In the first two experiments, participants had a limited amount of time to find a target line among distractors lines. We systematically varied the orientation of the target and the angular difference between the target and distractors. We find vertical, horizontal, and 45° targets require the least target/distractor angular difference to be found reliably and that the rate at which increases in target/distractor difference decrease search difficulty to be independent of target identity. Unexpectedly, even when the angular difference between the target and distractors was large, search performance was never optimal when the target orientation was 45°. A third experiment investigates this unexpected finding by correlating target/distractor difference and error rate with performance on tasks that measure a specific perceptual or cognitive ability. We find that the elevated error rate is correlated with performance on stimulus recognition and identification tasks, while the amount of target/distractor difference needed to detect the target reliably is correlated with performance on a stimulus reproduction task. We conclude that the target/distractor difference reveals the number of orientation categories in visual search, and, accordingly, that there are four such categories: two strong ones centred on 0° and 90° and two weak ones centred on 45° and 135°.     

Modeling visual attention

Quantitative modeling of psychological data is both technically and mathematically challenging. The present article introduces a user friendly and flexible program package that enables quantitative fits of Bundesen’s (1990) theory of visual attention to behavioral data from whole and partial report experiments. The program package is based on new computational formulas that are more general than previous ones and has already been used successfully in a number of neuropsychological investigations of attentional disorders, such as visual neglect and simultanagnosia. A clinical version of the program package is currently under development.     

Automatizing of visual attention

Perceptual automatizing was argued to occur as a consequence of repeated experience with a stimulus. Automatizing was hypothesized to entail a stereotyping in sampling of sensory information together with an attendant decrease in the rate of sampling of that information. An experiment was performed in which human Ss observed stimulus pictures for several trials, during which records were made of their visual fixations. It was found that fixation rate habituated and that this habituation was accompanied by a reduction in the uncertainty (entropy) of the spatial distributions of fixations. These results were interpreted as evidence for automatizing of visual fixation processes. Analysis of eye-movement distances suggested a possible mechanism for the reported loss of vividness of a stimulus which is perceived habitually.     

Dynamic states in working memory modulate guidance of visual attention: Evidence from an n-back paradigm

Items held in working memory (WM) can automatically bias attention when they reappear in visual displays. Recent evidence, however, suggests that WM biases of attention may be reduced under certain conditions, for example with increasing memory load. We employed a dual task paradigm to investigate how WM biases are affected by dynamic updating of memory contents. 1-back and 2-back versions of a memory task with colour stimuli were interrupted at intervals by an unrelated visual search task. Reappearance in the search display of the item that was currently active in WM guided attention, while suppressed or inactive items did not. We conclude that the rapid updating of memory contents facilitates the shifting of memory representations into different activity states on a moment-to-moment basis. The finding is consistent with models that propose that only one item can be “active” in WM at any one time to guide attention.     

Between-object binding and visual attention

Many previous studies have found that we can attend pairs of visual features (e.g., colour, orientation) more efficiently when they belong to the same “object” compared to when they belong to separate, neighbouring objects (e.g., Behrmann, Zemel, & Mozer, 1998; Egly, Rafal, & Driver, 1994). This advantage for attending features from the same object may reflect stronger binding between these features than arises for pairs of features belonging to separate objects. However, recent findings described by Davis, Welch, Holmes, and Shepherd (in press) suggest that under specific conditions this same-object advantage can be reversed, such that attention now spreads more readily between features belonging to separate neighbouring objects than between features of the same object. In such cases it would appear that features belonging to separate visual objects are more strongly bound than features of the same object. Here I review these findings and present the results of a new study. Together these data suggest that magnocellular processes in the human visual system bind together features from separate objects, whereas parvocellular processes bind together features from the same object.     

Object-based auditory and visual attention

Theories of visual attention argue that attention operates on perceptual objects, and thus that interactions between object formation and selective attention determine how competing sources interfere with perception. In auditory perception, theories of attention are less mature and no comprehensive framework exists to explain how attention influences perceptual abilities. However, the same principles that govern visual perception can explain many seemingly disparate auditory phenomena. In particular, many recent studies of 'informational masking' can be explained by failures of either auditory object formation or auditory object selection. This similarity suggests that the same neural mechanisms control attention and influence perception across different sensory modalities.     

Semantic guidance of attention within natural scenes

When viewing real-world scenes composed of a myriad of objects, detecting changes can be quite difficult, especially when transients are masked. In general, changes are noticed more quickly and accurately if they occur at the currently (or a recently) attended location. Here, we examine the effects of explicit and implicit semantic cues on the guidance of attention in a change detection task. Participants first attempted to read aloud a briefly presented prime word, then looked for a difference between two alternating versions of a real-world scene. Helpful primes named the object that changed, while misdirecting primes named another (unchanging) object in the picture. Robust effects were found for both explicit and implicit priming conditions, with helpful primes yielding faster change detection times than misdirecting or neutral primes. This demonstrates that observers are able to use higher order semantic information as a cue to guide attention within a natural scene, even when the semantic information is presented outside of explicit awareness.