Attention demands of visual search

The relation between attention demand and the number of items in the array (array size) was investigated by engaging subjects in a primary search task and measuring spare capacity at different points in time, with a secondary tone task that occurred randomly on half of the trials. The major variables in both tasks were array size 14, 8, or 12 letters and stimulus onset asynchrony (SOA: ?400, ?200, 0, 200, 400, and 600 msec. Subjects were able to perform the tasks quite independently, and me, st of the interference that resulted from nonindependence appeared in tone-task performance. Theamount of interference (i.e., maximum tone reaction time) was independent of array size, but theduration of interference (li.e., the number of SOAs at which tone reaction time was elevated) increased with array size. The findings were interpreted as supporting unlimited-capacity models of visual search performance.     

Task demands and limb apraxia in stroke

The present study was designed to examine the frequency and severity of apraxia in patients with left- or right-hemisphere stroke in both pantomime and imitation conditions and to compare the frequency of apraxia in each stroke group across the three patterns of apraxia described in Roy's model (Roy, 1996). Ninety-nine stroke patients and 15 age-matched healthy adults performed eight transitive gestures to pantomime and to imitation. Gestural performance was quantified as accuracy on five performance dimensions; a composite score, an arithmetic combination of the five performance dimensions, was used as an index of the overall accuracy. Analyses revealed a comparable proportion of patients in each stroke group were classified as apraxic in the imitation condition, but a higher proportion of left stroke patients were apraxic in the pantomime condition. The severity of apraxia in each stroke group and the performance dimensions affected were, however, comparable. Analyses of the patterns of apraxia (pantomime alone, imitation alone or apraxia in both conditions) revealed a higher frequency of apraxia in both stroke groups for the pattern reflecting apraxia in both conditions, indicating that a disruption at the movement execution stage of gesture performance was most common.     

Task demands and representation in long-term repetition priming

The effects of task demands on the representation of letter strings in long-term repetition priming (LTRP) were explored in two lexical decision experiments. The stimuli in both experiments were words and nonwords, some presented horizontally and some vertically. The only difference between the two experiments was the response required by the participant. In Experiment 1, the participants pressed one of two buttons, indicating whether or not a given stimulus was a word. In Experiment 2, the participants pressed one of four buttons, indicating both the lexical status and the orientation of a given stimulus. The results were that in Experiment 1, LTRP was not disrupted by a change in stimulus orientation, whereas in Experiment 2 it was, suggesting that the nature of the stimulus representation utilized in LTRP is partially dependent on the demands of the task.     

Task demands control acquisition and storage of visual information

Attention and working memory limitations set strict limits on visual representations, yet researchers have little appreciation of how these limits constrain the acquisition of information in ongoing visually guided behavior. Subjects performed a brick sorting task in a virtual environment. A change was made to 1 of the features of the brick being held on about 10% of trials. Rates of change detection for feature changes were generally low and depended on the pick-up and put-down relevance of the feature to the sorting task. Subjects' sorting decision suggests that changes may be missed because of a failure to update the changed feature. The authors also explore how hand and eye behavior are coordinated for strategic acquisition and storage of visual information throughout the task.     

Amount and duration of attentional demands during visual search

Previous research has suggested that, in visual-search tasks, the comparison between target and display items does not require attentional capacity. In the present experiment we used a secondary-task paradigm to distinguish the amount and duration of the attentional demands of visual search. The subjects performed visual search (the primary task) and tone detection (the secondary task) concurrently over the course of five experimental sessions (1,440 trials). For each subject, target-response mapping was either consistent or varied for Days 1-5. The results indicate that the amount of attentional demand, as reflected in secondary-task performance, increased as a function of display size in the search task. Switching from consistent to varied mapping in a sixth experimental session increased both the amount and the duration of the attentional demands of the search. The present results support models of visual-search performance in which the comparison of target and display items requires attentional capacity.     

Effect of template complexity on visual search and dual-task performance

Even dissimilar tasks interfere with one another when done together. We used visual search to examine the underlying cause of such interference. In many models, visual search is a process of biased competition controlled by a template describing the target to be sought. When the display is processed, matching against this template guides attention to the target. We show that increasing template complexity increased interference with a dissimilar concurrent task, story memory. This result was independent of reaction time: Increases in template complexity were associated with no increase in search time in Experiment 1 and with a decrease in search time in Experiment 2. The results show that the dual-task demands of visual search reflect the complexity of the template used in task control, and that this factor can be isolated from other sources of difficulty.     

Top-down search strategies determine attentional capture in visual search: Behavioral and electrophysiological evidence

To investigate how attentional capture in visual search is affected by generalized top-down search strategies, ERPs and behavioral performance were measured in two experiments where spatially nonpredictive color singleton cues preceded visual search arrays that contained one of two equally likely color singletons. When both singletons served as targets, irrelevant-color singleton cues produced behavioral attentional capture effects and elicited an N2pc component, indicative of a singleton search mode. When responses were required to only one of the two color singletons, the same cues no longer elicited behavioral spatial cuing effects, and the N2pc to these cues was attenuated and delayed, in line with the hypothesis that search was now guided by a feature-specific search strategy. Results demonstrate that the ability of visual singleton stimuli to capture attention is not simply determined by their bottom-up salience, but strongly modulated by top-down task sets.     

Task set flexibility and feature specificity modulate the limits of temporal attention

The consequences of maintaining a task set in the context of the (speeded) attentional blink were investigated in a series of experiments. Observers were asked to either attend or ignore the first of two target stimuli (T1 and T2). The results showed that when T1 and T2 shared a task relevant feature that was unique to T2, but not to T1, a shallow attentional blink was observed, as well as a lack of Lag 1 sparing. In comparison, when the targets shared a feature that was uniquely task relevant to both targets, the blink could not be avoided. Conversely, when no feature was shared between targets, ignoring T1 was successful and virtually no attentional costs were apparent. A similar lack of costs was also observed when targets shared a task relevant feature that was unique to T1 but not to T2. Finally, matching the feature dimension of a target feature that was unique to T2, but not T1, also strongly attenuated the blink. However, it did not completely abolish Lag 1 sparing. The results are interpreted in the context of current models of the attentional blink.     

Practice in visual search produces decreased capacity demands but increased distraction

Lavie (1995) proposed a load account of selective attention, which holds that spare capacity is involuntarily allocated to the processing of irrelevant stimuli. In support of this account, Lavie and Cox (1997) combined a letter search task with a flanker task and found that increasing load (search set size) resulted in decreased interference from an irrelevant distractor letter. In three experiments using a very similar procedure, we varied distractor location and distractor distinctiveness and observed that as load increased (from set size 2 to set size 6), there was a consistent reduction in interference. Critically, we addressed a fundamental hypothesis derived from the load account-that practice reduces capacity demands. This hypothesis leads to the rather counterintuitive prediction that as performance improves with practice, distractor processing should actually increase. Indeed, we found that interference in a high-load condition (set size 6), but not in a low-load condition (set size 2), did increase with practice. We describe a two-stage dilution account of attention that accommodates these results.     

Learning in combined-feature search: specificity to orientation

We investigated the dynamics and specificity of learning in the search for a target defined by combined features belonging to the same dimension (a rotated L) among homogeneous or heterogeneous distractors (differently rotated Ls). We found that learning makes searching faster although the search strategy does not change, remaining parallel with homogeneous distractors and serial with heterogeneous distractors. Learning was found to be specific for combined-feature orientation, although simple features did not change in the transfer stimulus: Transfer was partial when either the target or the distractors were rotated (so that their global orientation became the same) and totally absent when target and distractors were swapped. These results, which apply to searches among both homogeneous and heterogeneous distractors, rule out the possibility that learning is specific for orientation of just simple features. Instead, the results suggest that specificity of learning with combined features reflects the activation of junction detectors responding to a combined feature of a particular orientation.     

Task demands and age‐related differences in retrieval and response inhibition

This study investigates the role of task demands on children's ability to inhibit irrelevant information using a block‐cued directed‐forgetting task. Recall performance was compared in a block‐cued directed‐forgetting task in which task demands had been decreased by presenting blocks of semantically related words with that in which unrelated words were presented. Inhibition patterns of recall were found at a younger age in the task that contained the related words than in the task that contained the unrelated words. These results suggest that previous results charting the development of cognitive inhibition may not have been exclusively the product of the development of inhibition, but rather a product of both the difficulty of the task and the development of inhibition.     

The involvement of central attention in visual search is determined by task demands

Attention, the mechanism by which a subset of sensory inputs is prioritized over others, operates at multiple processing stages. Specifically, attention enhances weak sensory signal at the perceptual stage, while it serves to select appropriate responses or consolidate sensory representations into short-term memory at the central stage. This study investigated the independence and interaction between perceptual and central attention. To do so, I used a dual-task paradigm, pairing a four-alternative choice task with a visual search task. The results showed that central attention for response selection was engaged in perceptual processing for visual search when the number of search items increased, thereby increasing the demand for serial allocation of focal attention. By contrast, central attention and perceptual attention remained independent as far as the demand for serial shifting of focal attention remained constant; decreasing stimulus contrast or increasing the set size of a parallel search did not evoke the involvement of central attention in visual search. These results suggest that the nature of concurrent visual search process plays a crucial role in the functional interaction between two different types of attention.     

The influence of power on the information search, impression formation, and demands in negotiation

Based on work by Fiske (1992), we argue that power differences influence information search strategies during negotiation. Experiment 1 showed that negotiators with less power ask more diagnostic than leading questions, and more belief-congruent than incongruent questions, when facing a competitive rather than cooperative partner. Experiment 2 suggested that this result was caused by stronger accuracy and impression motivation among less powerful negotiators. Experiment 3 showed that belief-congruent rather than incongruent questions produce more positive impressions during negotiation. And when less powerful negotiators are asked leading questions about their willingness to cooperate (compete), they responded with lower (higher) demands. The results are discussed in terms of a motivated information-processing model of negotiation.     

Informative cues can slow search: The cost of matching a specific template

During visual search, observers hold in mind a search template, which they match against the stimulus. To characterize the content of this template, we trained observers to discriminate a set of artificial objects at an individual level and at a category level. The observers then searched for the objects on backgrounds that camouflaged the features that defined either the object’s identity or the object’s category. Each search stimulus was preceded by the target’s individual name, its category name, or an uninformative cue. The observers’ task was to locate the target, which was always present and always the only figure in the stimulus. The results showed that name cues slowed search when the features associated with the name were camouflaged. Apparently, the observers required a match between their mental representation of the target and the stimulus, even though this was unnecessary for the task. Moreover, this match involved all distinctive features of the target, not just the features necessary for a definitive identification. We conclude that visual search for a specific target involves a verification process that is performed automatically on all of the target’s distinctive features.     

Spatial exploration patterns determine navigation efficiency: Trade-off between memory demands and distance travelled

A total of 41 participants explored a novel square-shaped environment containing five identical boxes each hiding a visually distinct object. After an initial free exploration the participants were required to locate the objects first in a predetermined and subsequently in an optional order task. Two distinct exploration strategies emerged: Participants explored either along the main axes of the room (axial), or in a more spatially spread, circular pattern around the edges of the room (circular). These initial exploration strategies influenced the optimality of spatial navigation performance in the subsequent optional order task. The results reflect a trade-off between memory demands and distance efficiency. The more sequential axial strategy resulted in fewer demands on spatial memory but required more distance to be travelled. The circular strategy was more demanding on memory but required less subsequent travelling distance. The findings are discussed in terms of spatial knowledge acquisition and optimality of strategy representations.     

Spatial exploration patterns determine navigation efficiency: trade-off between memory demands and distance travelled

A total of 41 participants explored a novel square-shaped environment containing five identical boxes each hiding a visually distinct object. After an initial free exploration the participants were required to locate the objects first in a predetermined and subsequently in an optional order task. Two distinct exploration strategies emerged: Participants explored either along the main axes of the room (axial), or in a more spatially spread, circular pattern around the edges of the room (circular). These initial exploration strategies influenced the optimality of spatial navigation performance in the subsequent optional order task. The results reflect a trade-off between memory demands and distance efficiency. The more sequential axial strategy resulted in fewer demands on spatial memory but required more distance to be travelled. The circular strategy was more demanding on memory but required less subsequent travelling distance. The findings are discussed in terms of spatial knowledge acquisition and optimality of strategy representations.     

Looking sharp: Becoming a search template boosts precision and stability in visual working memory

Visual working memory (VWM) plays a central role in visual cognition, and current work suggests that there is a special state in VWM for items that are the goal of visual searches. However, whether the quality of memory for target templates differs from memory for other items in VWM is currently unknown. In this study, we measured the precision and stability of memory for search templates and accessory items to determine whether search templates receive representational priority in VWM. Memory for search templates exhibited increased precision and probability of recall, whereas accessory items were remembered less often. Additionally, while memory for Templates showed benefits when instances of the Template appeared in search, this benefit was not consistently observed for Accessory items when they appeared in search. Our results show that becoming a search template can substantially affect the quality of a representation in VWM.     

Emotional expressions and visual search efficiency: specificity and effects of anxiety symptoms

Although facial expressions are thought to vary in their functional impact on perceivers, experimental demonstration of the differential effects of facial expressions on behavior are lacking. In the present study, we examined the effects of exposure to facial expressions on visual search efficiency. Participants (n = 31) searched for a target in a 12 location circle array after exposure to an angry, disgusted, fearful, happy, or neutral facial expression for 100 ms or 500 ms. Consistent with predictions, exposure to a fearful expression prior to visual search resulted in faster target identification compared to exposure to other facial expressions. The effects of other facial expressions on visual search did not differ from each other. The fear facilitating effect on visual search efficiency was observed at 500-ms but not at 100-ms presentations, suggesting a specific temporal course of the facilitation. Subsequent analysis also revealed that individual differences in fear of negative evaluation, trait anxiety, and obsessive-compulsive symptoms possess a differential pattern of association with visual search efficiency. The experimental and clinical implications of these findings are discussed.     

Task demands and the pressures of everyday life: associations between cardiovascular reactivity and work blood pressure and heart rate.

Associations between cardiovascular stress reactivity and blood pressure and heart rate recorded in everyday life were hypothesized to depend on the stressfulness of the ambulatory monitoring period relative to standardized tasks and on activity levels at the time of measurement. One hundred two female and 60 male school teachers carried out high- and low-demand tasks under standardized conditions and ambulatory monitoring during the working day. Stress ratings during the day were close to those recorded during the low-demand task. Reactions to the low-demand task were significant predictors of ambulatory blood pressure and heart rate independent of baseline, age, gender, and body mass. Associations were more consistent for ambulatory recordings taken when participants were seated than when they were standing and when the ambulatory monitoring day was considered to be as stressful as usual or more stressful than usual, and not less stressful than usual. Laboratory-field associations of cardiovascular activity depend in part on the congruence of stressfulness and physical activity level in the 2 situations.