Types Of Visual Search Research Articles

Reading problems and their connection with visual search and attention.

Attention has been hypothesized to act as a sequential gating mechanism for the orderly processing of letters and words. These same visuoattentional processes are often assumed to partake in some but not all types of visual search. In the current study, 24 dyslexic and 36 typical readers completed an attentionally demanding visual conjunction search. Visual feature search served as an internal control. It has been suggested that reading problems should go hand in hand with specific problems in visual conjunction search-particularly elevated conjunction search slopes (time per search item)-often interpreted as a problem with visual attention. Results showed that reading problems were associated with slower visual search, especially conjunction search. However, reading deficits were not associated with increased conjunction search slopes but instead with increased search intercepts, traditionally not interpreted as reflecting attention. We discuss these results in the context of hypothesized visuoattentional problems in dyslexia. Remaining open to multiple interpretations of the data, the current study demonstrates that difficulties in visual search are associated with reading problems, in accordance with growing literature on visual cognition problems in developmental dyslexia.

Anti-saccades predict cognitive functions in older adults and patients with Parkinson's disease.

A major component of cognitive control is the ability to act flexibly in the environment by either behaving automatically or inhibiting an automatic behaviour. The interleaved pro/anti-saccade task measures cognitive control because the task relies on one’s abilities to switch flexibly between pro and anti-saccades, and inhibit automatic saccades during anti-saccade trials. Decline in cognitive control occurs during aging or neurological illnesses such as Parkinson’s disease (PD), and indicates decline in other cognitive abilities, such as memory. However, little is known about the relationship between cognitive control and other cognitive processes. Here we investigated whether anti-saccade performance can predict decision-making, visual memory, and pop-out and serial visual search performance. We tested 34 younger adults, 22 older adults, and 20 PD patients on four tasks: an interleaved pro/anti-saccade, a spatial visual memory, a decision-making and two types of visual search (pop-out and serial) tasks. Anti-saccade performance was a good predictor of decision-making and visual memory abilities for both older adults and PD patients, while it predicted visual search performance to a larger extent in PD patients. Our results thus demonstrate the suitability of the interleaved pro/anti-saccade task as a cognitive marker of cognitive control in aging and PD populations.

Modeling search guidance: Three parameters for characterizing performance in different types of visual search.

Modeling search guidance: Three parameters for characterizing performance in different types of visual search.

Top-down but not bottom-up visual scanning is affected in hereditary pure cerebellar ataxia.

The aim of this study was to clarify the nature of visual processing deficits caused by cerebellar disorders. We studied the performance of two types of visual search (top-down visual scanning and bottom-up visual scanning) in 18 patients with pure cerebellar types of spinocerebellar degeneration (SCA6: 11; SCA31: 7). The gaze fixation position was recorded with an eye-tracking device while the subjects performed two visual search tasks in which they looked for a target Landolt figure among distractors. In the serial search task, the target was similar to the distractors and the subject had to search for the target by processing each item with top-down visual scanning. In the pop-out search task, the target and distractor were clearly discernible and the visual salience of the target allowed the subjects to detect it by bottom-up visual scanning. The saliency maps clearly showed that the serial search task required top-down visual attention and the pop-out search task required bottom-up visual attention. In the serial search task, the search time to detect the target was significantly longer in SCA patients than in normal subjects, whereas the search time in the pop-out search task was comparable between the two groups. These findings suggested that SCA patients cannot efficiently scan a target using a top-down attentional process, whereas scanning with a bottom-up attentional process is not affected. In the serial search task, the amplitude of saccades was significantly smaller in SCA patients than in normal subjects. The variability of saccade amplitude (saccadic dysmetria), number of re-fixations, and unstable fixation (nystagmus) were larger in SCA patients than in normal subjects, accounting for a substantial proportion of scattered fixations around the items. Saccadic dysmetria, re-fixation, and nystagmus may play important roles in the impaired top-down visual scanning in SCA, hampering precise visual processing of individual items.

Object-based selection modulates top-down attentional shifts

A large body of evidence supports that visual attention – the cognitive process of selectively concentrating on a salient or task-relevant subset of visual information – often works on object-based representation. Recent studies have postulated two possible accounts for the object-specific attentional advantage: attentional spreading and attentional prioritization, each of which modulates a bottom-up signal for sensory processing and a top-down signal for attentional allocation, respectively. It is still unclear which account can explain the object-specific attentional advantage. To address this issue, we examined the influence of object-specific advantage on two types of visual search: parallel search, invoked when a bottom-up signal is fully available at a target location, and serial search, invoked when a bottom-up signal is not enough to guide target selection and a top-down control for shifting of focused attention is required. Our results revealed that the object-specific advantage is given to the serial search but not to the parallel search, suggesting that object-based attention facilitates stimulus processing by affecting the priority of attentional shifts rather than by enhancing sensory signals. Thus, our findings support the notion that the object-specific attentional advantage can be explained by attentional prioritization but not attentional spreading.

Working Memory Representation Does Guide Visual Attention: Evidence from Eye Movements

Whether the working memory representations could guide visual attention to select the matching stimuli in visual search is still controversial.By requiring the participants to perform a visual search task while online keeping some objects in working memory,some researchers have observed a stronger interference from the distractor when it was identical or related to the object held in memory.But other researchers did not observe such attentional guidance effect even using similar procedures.Olivers(2009) examined several possible influencing factors through a series of experiments and finally attributed the discrepancy to the search type whether the search target was varied or not across trials throughout the experiment.However,according to our analysis,there were several factors might confound the results in the critical experiment of Olivers(2009).So here,we used the classic dual task combined with eye movement tracking technology to reexamine and evaluate the effect of the search type on the top-down guiding process of visual attention from working memory representations.Experiment 1 aimed to reexamine the effect of search type on attentional guidance via counterbalancing the perceptual difficulty of the search array in two types of the visual search task.The experimental procedure was similar to that used in the Experiment 5 of Olivers(2009) except making the perceptual difficulty of search array to be equal between visual search tasks.The eye movement data showed that,both in fixed-and varied-target visual search task,the distractor which was identical to the working memory representation was more easily to capture visual attention than the control distractor which was irrelevant to the working memory representations.It is suggested that the attentional guidance would appear no matter which visual search type used.However,we also found that the magnitude of attentional guidance was greater in the fixed-target visual search task than in the varied-target visual search task.Experiment 2 aimed to examine whether search type or working memory load was the real fact which caused the difference of guidance effect between visual search tasks in experiment 1.In the present experiment,we counterbalanced the working memory load between two types of visual search task.Consistent to experiment 1,the results also showed significant attentional guidance in both visual search task,however,the magnitude of the attentional guidance between visual search tasks became equivalent.In conclusion,these results disobeyed the explanation that the visual search type was the determinant factor for whether the attentional guidance has been observed or not in the previous studies,and suggested that the attentional guidance from working memory was to some degree affected by the factors of working memory load.

The transfer of abstract attentional sets across different types of visual search

The transfer of abstract attentional sets across different types of visual search

New insights into feature and conjunction search: I. Evidence from pupil size, eye movements and ageing

Differences in the processing mechanisms underlying visual feature and conjunction search are still under debate, one problem being a common emphasis on performance measures (speed and accuracy) which do not necessarily provide insights to the underlying processing principles. Here, eye movements and pupil dilation were used to investigate sampling strategy and processing load during performance of a conjunction and two feature-search tasks, with younger (18–27 years) and healthy older (61–83 years) age groups compared for evidence of differential age-related changes. The tasks involved equivalent processing time per item, were controlled in terms of target–distractor similarity, and did not allow perceptual grouping. Close matching of the key tasks was confirmed by patterns of fixation duration and an equal number of saccades required to find a target. Moreover, moment-to-moment pupillary dilation was indistinguishable across the tasks for both age groups, suggesting that all required the same total amount of effort or resources. Despite matching, subtle differences in eye movement patterns occurred between tasks: the conjunction task required more saccades to reach a target-absent decision and involved shorter saccade amplitudes than the feature tasks. General age-related changes were manifested in an increased number of saccades and longer fixation durations in older than younger participants. In addition, older people showed disproportionately longer and more variable fixation durations for the conjunction task specifically. These results suggest a fundamental difference between conjunction and feature search: accurate target identification in the conjunction context requires more conservative eye movement patterns, with these further adjusted in healthy ageing. The data also highlight the independence of eye movement and pupillometry measures and stress the importance of saccades and strategy for understanding the processing mechanisms driving different types of visual search.

Early vision and visual attention

The question whether visual perception is spontaneous, sudden or is running through several phases, mediated by higher cognitive processes, was raised ever since the early work of Gestalt psychologists. In the early 1980s, Treisman proposed the feature integration theory of attention (FIT), based on the findings of neuroscience. Soon after publishing her theory a new scientific approach appeared investigating several visual perception phenomena. The most widely researched were the key constructs of FIT, like types of visual search and the role of the attention. The following review describes the main studies of early vision and visual attention.

Visual Search Processes in Healthy Aging

It is well established that there are two limiting types of visual search, a pre-attentive parallel and an attention-related serial process. Such different types of processing may depend upon different regions of the visual cortex and such a measurable dissociation of function could provide a useful marker for particular types of cortical pathology, such as that associated with Parkinson's disease, aging, and Alzheimer's disease. For example, recent studies in this laboratory have shown that people with Parkinson's disease have abnormal parallel but normal serial search functions. Plude and Doussard-Roosevelt (1989 Psychology and Aging4 98 – 105) found no difference in parallel processing between older and young adults, but found that older adults performed worse on a conjunction task. The aim of the present experiment was to extend this research and look at the effect of aging on other types of visual search task and to compare these findings to patients with Parkinson's disease and Alzheimer's disease to determine if different patterns of visual function occur. Twenty-five young adults (mean age 32.6 years) and twenty-five older adults (mean age 63.4 years) performed both a conjunction task and a task involving the detection of a target only slightly larger than the distractors (the ‘size’ task). Our hypothesis was that for both types of visual search there would be an increase in search slope in the older adult group compared to the younger adults. Results of a 2-factor (1 between and 1 within) ANOVA performed on the slope values indicate statistically significant main effects of both age ( F=7.661, p<0.008) and search task ( F=25.426, p<0.0001), where in both the conjunction and size task the slope value was significantly greater for the older than for the younger adults. The slope for the size task was significantly greater than that for the conjunction task for both age groups. The results therefore support our hypothesis and further work is in progress to determine the effects of Alzheimer's disease on different types of visual search processing.

Modeling the role of parallel processing in visual search

Treisman's Feature Integration Theory and Julesz's Texton Theory explain many aspects of visual search. However, these theories require that parallel processing mechanisms not be used in many visual searches for which they would be useful, and they imply that visual processing should be much slower than it is. Most importantly, they cannot account for recent data showing that some subjects can perform some conjunction searches very efficiently. Feature Integration Theory can be modified so that it accounts for these data and helps to answer these questions. In this new theory, which we call Guided Search, the parallel stage guides the serial stage as it chooses display elements to process. A computer simulation of Guided Search produces the same general patterns as human subjects in a number of different types of visual search.