Spatial organization to facilitate action.

Humans exert a great deal of control over our local environments-selecting and arranging the many objects around us on the basis of conflicting task-demands, aesthetic preferences, and habitual convenience. Because routine behaviour necessitates that we regularly find and access these objects, the particular arrangements we choose can influence the likelihood and difficulty of engaging in different tasks and actions. Despite this importance, relatively little research has directly examined human organizational behaviours and tendencies. Here we investigate how objects in a computer-based search task are freely and dynamically arranged by participants over time, while manipulating the statistics of the target sequence. We report common organizational behaviours including reduction of distance between targets as well as separation of target subsets with high community. However, the extent of these behaviours and their relationship to individual differences in performance varies as a function of the target sequence structure. In particular, tasks composed of a larger number of smaller groups of targets lead to better organizational and performance outcomes than tasks composed of fewer larger groups.

Re-reading after mind wandering.

Though much research has been conducted on the causes and processes underlying mind wandering, relatively little has addressed what happens after an episode of mind wandering. We explore this issue in the context of reading. Specifically, by examining re-reading behaviours following mind wandering episodes. Results from 2 studies reveal that after mind wandering, participants re-read nearly half the time. This re-reading occurs whether mind wandering is self-caught or probe-caught, and it typically involves retracing a line or 2 of text. Based on subjective reports, it appears that individuals re-read when they feel that clarification of the text is needed, suggesting that a key concept of the text is missed during a mind wandering episode. Future work aimed at understanding how individuals refocus their attention following mind wandering in different settings should provide additional insights into the fluctuation of attentional focus and the immediate impact of a mind wandering episode. (PsycINFO Database Record

Eye and head movements are complementary in visual selection.

In the natural environment, visual selection is accomplished by a system of nested effectors, moving the head and body within space and the eyes within the visual field. However, it is not yet known if the principles of selection for these different effectors are the same or different. We used a novel gaze-contingent display in which an asymmetric window of visibility (a horizontal or vertical slot) was yoked to either head or eye position. Participants showed highly systematic changes in behaviour, revealing clear differences in the principles underlying selection by eye and head. Eye movements were more likely to move in the direction of visible information-horizontally when viewing with a horizontal slot, and vertically with a vertical slot. Head movements showed the opposite and complementary pattern, moving to reveal new information (e.g. vertically with a horizontal slot and vice versa). These results are consistent with a nested system in which the head favours exploration of unknown regions, while the eye exploits what can be seen with finer-scale saccades.

Spatial partitions systematize visual search and enhance target memory.

Humans are remarkably capable of finding desired objects in the world, despite the scale and complexity of naturalistic environments. Broadly, this ability is supported by an interplay between exploratory search and guidance from episodic memory for previously observed target locations. Here we examined how the environment itself may influence this interplay. In particular, we examined how partitions in the environment-like buildings, rooms, and furniture-can impact memory during repeated search. We report that the presence of partitions in a display, independent of item configuration, reliably improves episodic memory for item locations. Repeated search through partitioned displays was faster overall and was characterized by more rapid ballistic orienting in later repetitions. Explicit recall was also both faster and more accurate when displays were partitioned. Finally, we found that search paths were more regular and systematic when displays were partitioned. Given the ubiquity of partitions in real-world environments, these results provide important insights into the mechanisms of naturalistic search and its relation to memory.

Arranging Objects in Space: Measuring Task-Relevant Organizational Behaviors During Goal Pursuit.

Human behavior unfolds primarily in built environments, where the arrangement of objects is a result of ongoing human decisions and actions, yet these organizational decisions have received limited experimental study. In two experiments, we introduce a novel paradigm designed to explore how individuals organize task-relevant objects in space. Participants completed goals by locating and accessing sequences of objects in a computer-based task, and they were free to rearrange the positions of objects at any time. We measure a variety of organization changes and evaluate how these measures relate to individual differences in performance. In Experiment 1, we show that with weak structure in task demands, changes in object positions that arise through performance of the task lead to improved order, characterized predominantly by a centralization of frequently used items and a peripheralization of infrequently used objects. In Experiment 2, with increased task structure, we observe more refined organizational tendencies, with selective contraction and clustering of interrelated task-relevant objects. We further demonstrate that these more selective organization behaviors are reliably associated with individual differences in task performance. Collectively, these two studies reveal properties of space and of task demands that support and facilitate effective organization of the environment in support of ongoing behavior.

Endogenous strategy in exploration.

We examined the characteristics of endogenous exploratory behaviors in a generalized search task in which guidance signals (e.g., landmarks, semantics, visual saliency, layout) were limited or precluded. Individuals looked for the highest valued cell in an array and were scored on the quality of the best value they could find. Exploration was guided only by the cells that had been previously examined, and the value of this guidance was manipulated by adjusting spatial autocorrelation to produce relatively smooth and rough landscapes-that is, arrays in which nearby cells had unrelated values (low correlation = rough) or similar values (high correlation = smooth). For search in increasingly rough as compared with smooth arrays, we found reduced performance despite increased sampling and increased time spent searching after revelation of a searcher's best cell. Spatially, sampling strategies tended toward more excursive, branching, and space-filling patterns as correlation decreased. Using a novel generalized-recurrence analysis, we report that these patterns reflect an increase in systematic search paths, characterized by regularized sweeps with localized infilling. These tendencies were likewise enhanced for high-performance as compared with low-performance participants. The results suggest a trade-off between guidance (in smooth arrays) and systematicity (in rough arrays), and they provide insight into the particular strategic approaches adopted by searchers when exogenous guiding information is minimized.

Balancing energetic and cognitive resources: memory use during search depends on the orienting effector.

Search outside the laboratory involves tradeoffs among a variety of internal and external exploratory processes. Here we examine the conditions under which item specific memory from prior exposures to a search array is used to guide attention during search. We extend the hypothesis that memory use increases as perceptual search becomes more difficult by turning to an ecologically important type of search difficulty - energetic cost. Using optical motion tracking, we introduce a novel head-contingent display system, which enables the direct comparison of search using head movements and search using eye movements. Consistent with the increased energetic cost of turning the head to orient attention, we discover greater use of memory in head-contingent versus eye-contingent search, as reflected in both timing and orienting metrics. Our results extend theories of memory use in search to encompass embodied factors, and highlight the importance of accounting for the costs and constraints of the specific motor groups used in a given task when evaluating cognitive effects.

Running the figure to the ground: figure-ground segmentation during visual search.

We examined how figure-ground segmentation occurs across multiple regions of a visual array during a visual search task. Stimuli consisted of arrays of black-and-white figure-ground images in which roughly half of each image depicted a meaningful object, whereas the other half constituted a less meaningful shape. The colours of the meaningful regions of the targets and distractors were either the same (congruent) or different (incongruent). We found that incongruent targets took longer to locate than congruent targets (Experiments 1, 2, and 3) and that this segmentation-congruency effect decreased when the number of search items was reduced (Experiment 2). Furthermore, an analysis of eye movements revealed that participants spent more time scrutinising the target before confirming its identity on incongruent trials than on congruent trials (Experiment 3). These findings suggest that the distractor context influences target segmentation and detection during visual search.

Comparing target detection errors in visual search and manually-assisted search.

Subjects searched for low- or high-prevalence targets among static nonoverlapping items or items piled in heaps that could be moved using a computer mouse. We replicated the classical prevalence effect both in visual search and when unpacking items from heaps, with more target misses under low prevalence. Moreover, we replicated our previous finding that while unpacking, people often move the target item without noticing (the unpacking error) and determined that these errors also increase under low prevalence. On the basis of a comparison of item movements during the manually-assisted search and eye movements during static visual search, we suggest that low prevalence leads to broadly reduced diligence during search but that the locus of this reduced diligence depends on the nature of the task. In particular, while misses during visual search often arise from a failure to inspect all of the items, misses during manually-assisted search more often result from a failure to adequately inspect individual items. Indeed, during manually-assisted search, over 90 % of target misses occurred despite subjects having moved the target item during search.

In manually-assisted search, perception supervises rather than directs action.

During manually-assisted search, where participants must actively manipulate search items, it has been reported that participants will often select and move the target of search itself without recognizing it (Solman et al., 2012a). In two experiments we explore the hypothesis that this error results from a naturally-arising strategy that decouples perception and action during search, enabling motor interactions with items to outpace the speed of perceptual analysis. In Experiment 1, we report that the error is prevalent for both mouse and touch-screen interaction modes, and is uninfluenced by speeding or slowing instructions--ruling out these task-specific details as causes of the error. In Experiment 2 we manipulate motor speed, and show that reducing the speed of individual movements during search leads to a reduction in error rates. These findings support the conclusion that the error results from incoordination between motor and perceptual processes, with motor processes outpacing perceptual abilities.

A methodological note on evaluating performance in a sustained-attention-to-response task.

We evaluated the influence of speed-accuracy trade-offs on performance in the sustained attention to response task (SART), a task often used to evaluate the effectiveness of techniques designed to improve sustained attention. In the present study, we experimentally manipulated response delay in a variation of the SART and found that commission errors, which are commonly used as an index of lapses in sustained attention, were a systematic function of manipulated differences in response delay. Delaying responses to roughly 800 ms after stimulus onset reduced commission errors substantially. We suggest the possibility that any technique that affects response speed will indirectly alter error rates independently of improvements in sustained attention. Investigators therefore need to carefully explore, report, and correct for changes in response speed that accompany improvements in performance or, alternatively, to employ tasks that control for response speed.

Changing perspective: zooming in and out during visual search.

Laboratory studies of visual search are generally conducted in contexts with a static observer vantage point, constrained by a fixation cross or a headrest. In contrast, in many naturalistic search settings, observers freely adjust their vantage point by physically moving through space. In two experiments, we evaluate behavior during free vantage point (FVP) search, using observer-controlled zooming to simulate movement toward or away from search objects. We focus on scope fluctuations--repeated reversals in the direction of zooming during search. We found increased fluctuation when search items were sparse (Experiment 1) or of mixed size (Experiment 2). We propose that during FVP search, observers attempt to maximize the number of simultaneously discriminable items. Scope fluctuations emerge when maximizing does not enable simultaneous access to all search items, or when observers become disoriented in the search environment, necessitating repeated switches to a broad scope to reorient.

Found and missed: failing to recognize a search target despite moving it.

We present results from five search experiments using a novel 'unpacking' paradigm in which participants use a mouse to sort through random heaps of distractors to locate the target. We report that during this task participants often fail to recognize the target despite moving it, and despite having looked at the item. Additionally, the missed target item appears to have been processed as evidenced by post-error slowing of individual moves within a trial. The rate of this 'unpacking error' was minimally affected by set size and dual task manipulations, but was strongly influenced by perceptual difficulty and perceptual load. We suggest that the error occurs because of a dissociation between perception for action and perception for identification, providing further evidence that these processes may operate relatively independently even in naturalistic contexts, and even in settings like search where they should be expected to act in close coordination.

Challenge and error: critical events and attention-related errors.

Attention lapses resulting from reactivity to task challenges and their consequences constitute a pervasive factor affecting everyday performance errors and accidents. A bidirectional model of attention lapses (error↔attention-lapse: Cheyne, Solman, Carriere, & Smilek, 2009) argues that errors beget errors by generating attention lapses; resource-depleting cognitions interfering with attention to subsequent task challenges. Attention lapses lead to errors, and errors themselves are a potent consequence often leading to further attention lapses potentially initiating a spiral into more serious errors. We investigated this challenge-induced error↔attention-lapse model using the Sustained Attention to Response Task (SART), a GO-NOGO task requiring continuous attention and response to a number series and withholding of responses to a rare NOGO digit. We found response speed and increased commission errors following task challenges to be a function of temporal distance from, and prior performance on, previous NOGO trials. We conclude by comparing and contrasting the present theory and findings to those based on choice paradigms and argue that the present findings have implications for the generality of conflict monitoring and control models.

Memory load affects visual search processes without influencing search efficiency.

Participants' eye-movements were monitored while they searched for a target among a varying number of distractors either with or without a concurrent memory load. Consistent with previous findings, adding a memory load slowed response times without affecting search slopes; a finding normally taken to imply that memory load affects pre- and/or post-search processes but not the search process itself. However, when overall response times were decomposed using eye-movement data into pre-search (e.g., initial encoding), search, and post-search (e.g., response selection) phases, analysis revealed that adding a memory load affected all phases, including the search phase. In addition, we report that fixations selected under load were more likely to be distant from search items, and more likely to be close to previously inspected locations. Thus, memory load affects the search process without affecting search slopes. These results challenge standard interpretations of search slopes and main effects in visual search.

Item-specific location memory in visual search.

In two samples, we demonstrate that visual search performance is influenced by memory for the locations of specific search items across trials. We monitored eye movements as observers searched for a target letter in displays containing 16 or 24 letters. From trial to trial the configuration of the search items was either Random, fully Repeated or similar but not identical (i.e., Intermediate). We found a graded pattern of response times across conditions with slowest times in the Random condition and fastest responses in the Repeated condition. We also found that search was comparably efficient in the Intermediate and Random conditions but more efficient in the Repeated condition. Importantly, the target on a given trial was fixated more accurately in the Repeated and Intermediate conditions relative to the Random condition. We suggest a tradeoff between memory and perception in search as a function of the physical scale of the search space.

Age trends for failures of sustained attention.

Recent research has revealed an age-related reduction in errors in a sustained attention task, suggesting that sustained attention abilities improve with age. Such results seem paradoxical in light of the well-documented age-related declines in cognitive performance. In the present study, performance on the sustained attention to response task (SART) was assessed in a supplemented archival sample of 638 individuals between 14 and 77 years old. SART errors and response speed appeared to decline in a linear fashion as a function of age throughout the age span studied. In contrast, other measures of sustained attention (reaction time coefficient of variation), anticipation, and omissions) showed a decrease early in life and then remained unchanged for the rest of the life span. Thus, sustained attention shows improvements with maturation in early adulthood but then does not change with aging in older adults. On the other hand, aging across the entire life span leads to a more strategic (i.e., slower) response style that reduces the overt and critical consequences (i.e., SART errors) of momentary task disengagement.

Anatomy of an error: a bidirectional state model of task engagement/disengagement and attention-related errors.

We present arguments and evidence for a three-state attentional model of task engagement/disengagement. The model postulates three states of mind-wandering: occurrent task inattention, generic task inattention, and response disengagement. We hypothesize that all three states are both causes and consequences of task performance outcomes and apply across a variety of experimental and real-world tasks. We apply this model to the analysis of a widely used GO/NOGO task, the Sustained Attention to Response Task (SART). We identify three performance characteristics of the SART that map onto the three states of the model: RT variability, anticipations, and omissions. Predictions based on the model are tested, and largely corroborated, via regression and lag-sequential analyses of both successful and unsuccessful withholding on NOGO trials as well as self-reported mind-wandering and everyday cognitive errors. The results revealed theoretically consistent temporal associations among the state indicators and between these and SART errors as well as with self-report measures. Lag analysis was consistent with the hypotheses that temporal transitions among states are often extremely abrupt and that the association between mind-wandering and performance is bidirectional. The bidirectional effects suggest that errors constitute important occasions for reactive mind-wandering. The model also enables concrete phenomenological, behavioral, and physiological predictions for future research.

The eyes fixate the optimal viewing position of task-irrelevant words.

We evaluated whether one's eyes tend to fixate the optimal viewing position (OVP) of words even when the words are task irrelevant and should be ignored. Participants completed the standard Stroop task, in which they named the physical color of congruent and incongruent color words without regard to the meanings of the color words. We monitored the horizontal position of the first eye fixation that occurred after the onset of each color word to evaluate whether these fixations would be at the OVP, which is just to the left of word midline. The results showed that (1) the peak of the distribution of eye fixation positions was to the left of the midline of the color words, (2) the majority of the fixations landed on the left side of the color words, and (3) the average leftward displacement of the first fixation from word midline was greater for longer color words. These results suggest that the eyes tend to fixate the OVP of words even when those words are task irrelevant.