Decomposing visual search: evidence of multiple item-specific skills

Four experiments demonstrated that visual search can be decomposed into two components: one consisting of skills shared with memory search and the other consisting of skills not shared with memory search. A training-transfer paradigm was used to test for transfer from memory search to visual search and vice versa. When the same targets and distractors were used in training and transfer, visual search practice completely trained memory search, but memory search practice only partially trained visual search. Learning on both the shared and the private components of visual search benefited more from item-specific training than from nonspecific training. The relationship between the components and some theorized models of visual search are discussed, particularly in terms of prioritization learning.     

Preconstancy information can influence visual search: The case of lightness constancy.

Can visual search be based on preconstancy representations of the scene—that is, ones in which accidental characteristics of the scene, such as shadows, point of view, and distance, have not yet been discounted? This question was addressed within the specific context of lightness constancy, the phenomenon that surface lightness is perceived as relatively unchanged despite changes in illumination conditions. Three experiments yielded evidence of preconstancy influence on visual search. This was true even when the preconstancy information that seemed to influence search was unavailable at a reportable level. The results suggest that visual search processes can be engaged before the processing that leads to the experienced perception of the scene is complete. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The scale bandwidth of visual search

Observers were asked to locate a target in a brief, two-scale display. Accuracy of locating the target was measured as a function of the ratio between the two scales. At each scale ratio, the probability of locating the target as a function of the number of elements is well fit by the idea that the observer accurately monitors only a "critical" number of elements. The dependence of critical number on scale ratio is well accounted for by a model that assumes that the observer's decision is based on an evenly spaced array of samples. The sample spacing is under attentional control, but is always uniform.     

Do the contents of visual working memory automatically influence attentional selection during visual search?

In many theories of cognition, researchers propose that working memory and perception operate interactively. For example, in previous studies researchers have suggested that sensory inputs matching the contents of working memory will have an automatic advantage in the competition for processing resources. The authors tested this hypothesis by requiring observers to perform a visual search task while concurrently maintaining object representations in visual working memory. The hypothesis that working memory activation produces a simple but uncontrollable bias signal leads to the prediction that items matching the contents of working memory will automatically capture attention. However, no evidence for automatic attentional capture was obtained; instead, the participants avoided attending to these items. Thus, the contents of working memory can be used in a flexible manner for facilitation or inhibition of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correlation of clinical history and electrodiagnostic abnormalities with outcome after surgery for carpal tunnel syndrome

A retrospective study on 294 wrists in 154 patients who had been diagnosed with carpal tunnel syndrome and subsequently had surgery performed was undertaken; both clinical and electrodiagnostic findings were correlated. The cases were divided into three groups based on electromyographic severity (mild, moderate, severe), and recovery from symptoms was evaluated after 1 week, 3 months, and 1 year. The cases were also divided into five groups based on symptom duration, and the same investigations were performed. All operations were conducted by applying the open release method with the limited-palmar incision technique. Operative outcomes showed no association between recovery from symptoms and the severity of electromyographic findings or the duration of symptoms, although the group that had the shortest duration of symptoms recovered faster than the long-duration groups statistically. Postoperative results after 1 year were also successful for those patients who had had symptoms of long duration. Of the 294 wrist operations studied, good to excellent postoperative outcomes were recorded in 242 cases (82 percent), fair outcomes in 39 cases (13 percent), and poor outcomes in 13 cases (4 percent). Patients whose electromyogram revealed double crush syndrome still showed improvement, with good-to-excellent results in 11 out of 15 cases (73 percent). Patients with diabetes mellitus also showed improvement, with good-to-excellent results in 14 out of 19 patients (74 percent). This study showed that postoperative results were satisfactory within 1 year, regardless of the degree of electromyographic severity, symptom duration, presence of diabetes mellitus, or double crush syndrome.     

The effects of practice on location cueing and visual search.

A target-detection experiment was conducted with 4 inexperienced college students to determine whether or not the magnitude of facilitative location cueing effects would change as a function of practice. Over the course of 5 test sessions, these effects attenuated. This suggests that practice decreases the influence of location cues on visual search performance and attentional processing. The authors propose that when participants perform cued visual search experiments and become familiar with potential target locations as a result of extended practice and automaticity, these locations are encoded in spatial memory by an operation called spatial indexing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The serial process in visual search.

The conditions for serial search are described. A multiple target search methodology (Thornton & Gilden, 2007) is used to home in on the simplest target/distractor contrast that effectively mandates a serial scheduling of attentional resources. It is found that serial search is required when (a) targets and distractors are mirror twins, and (b) when the search elements lack the Gestalt property of intrinsic orientation. The finding is put into the context of Feature Integration Theory (Treisman & Gelade, 1980) that first identified the occasions of serial search to be important to object perception and understanding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of adapting luminance on the latency of visual search

Computational models of attentional processing typically view the "attentional spotlight" as a winner-take-all network whose focus can be shifted serially about a display if required. As a result, lateral inhibition is assumed in these models to be an important mechanism involved in visual search. On the basis of this assumption, we predicted that changes in adapting luminance would produce specific changes in search latency functions in virtue of affecting visual inhibition. The results of our first two experiments confirmed these predictions: when search was difficult, and produced reaction time results characteristic of serial processing, there was a main effect of adapting luminance and a significant interaction between adapting luminance and the number of display elements. These effects were both reflected in increases in the slopes and the intercepts of average search latency functions when adapting luminance was decreased. When search was easy, and produced pop out effects characteristic of parallel processing, there were no significant effects of adapting luminance on search latency. The third experiment used adapting luminance to further explore the possibility that arrow junctions are detected preattentively. The results suggested that a visual search for such elements involves a substantial serial component, which weighs against the claim that they are detected by low-level vision.     

The guidance of eye movements during active visual search

An analysis of monkey eye movements in classic conjunction and feature search tasks was made. The task was to find and fixate a target in an array of stimuli. Saccades targeted stimuli accurately (red and green bars, 1.25 x 0.25 degrees), landing most of the time within 1.0 degree of the stimulus center and rarely in blank areas far from any stimulus. Monkeys used target color, but not orientation, to selectively guide search. Saccades moved the point of fixation on the average just beyond the area that could be examined by focal attentive mechanisms during the current fixation, as described in a previous paper (Motter BC, Belky EJ. The zone of focal attention during active visual search. Vis Res 1998;38:1007-22). This distance scales with the density of relevant stimuli in the scene. The saccade targeting data suggest that the locations of items of a particular color, but apparently not of a particular orientation, are available outside the region of focal attention. Color feature selection can apparently block the distracting effects of color unique distractors during search.     

Partitioning and saturation of visual displays and efficiency of visual search.

The time required to locate a constant number of signals (ten diamonds) in a square display when (a) the number of irrelevant signals (squares and circles) was varied from 10 to 70 and (b) the number of partitions in the display was varied by use of grid lines to produce a 9 X 9, 13 X 13, or 16 X 16 matrix was determined. Search time increased both when the number of irrelevant signals was increased and when the number of partitions was increased. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of age on consistent and varied semantic-category search performance.

Three experiments examined age-related consistent mapping (CM) and varied mapping (VM) practice effects. In separate experiments, young (age, 19–22), middle-aged (37–50), and older (64–88) adults' performance was examined using semantic-category and letter-based search paradigms. After extensive practice, major age differences occurred in CM search. Young and middle-aged subjects showed near-zero comparison slopes, large reductions in mean reaction times, and substantial reductions in response variability. Although older adults' reaction time decreased with CM practice, the reduction in reaction time, comparison slope, and response variability was small compared with the other groups. In VM search, older subjects were slower than the other age groups, but all groups exhibited similar linear set-size functions, search termination, and comparison-load effects. We concluded that age-associated declines in cognitive performance may be due in large part to the degree with which older adults can acquire or use automatic processes to perform tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversing visual search asymmetries with conjunctions of movement and orientation.

Many theories of visual search offer general principles intended to apply to search for targets defined by any stimulus attribute. The importance of considering specific properties of different visual subsystems is demonstrated by examining search for movement–orientation conjunctions. In displays of intermingled moving and stationary stimuli, search for a salient tilted target (45° vs vertical) is easier among moving than stationary stimuli. If a finer orientation distinction is required (9° vs vertical), the reverse is true; search is easier among the stationary. This follows from the known properties of visual subsystems specialized for processing moving or stationary stimuli. It is not predicted by general theories of visual search such as guided search or similarity theory, nor by principles of Gestalt grouping. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The natural history of hereditary multiple exostoses

We established a database of hereditary multiple exostoses for the state of Washington, on the basis of a retrospective review of the medical records and a clinical evaluation of family members, to determine the prevalence, clinical range of expression, and rate of malignant degeneration. The database comprised forty-six kindreds with 113 affected members; all kindreds had at least one member living in the state of Washington. The over-all prevalence was at least one in 50,000. Approximately 10 per cent of the subjects had no family history of multiple exostoses. With the use of twenty-three pedigrees that demonstrated an adequate multigenerational history for determination of penetrance of the gene, we identified one unaffected individual among twenty-six obligate heterozygotes, a rate of penetrance of 96 per cent. There was no evidence for a substantial reduction of penetrance in female subjects. The median age at the time of the diagnosis in the 113 affected individuals was three years (range, birth to twelve years). In a cohort of eighty-four subjects for whom we had complete information, the clinical range of expression was wide: thirty-three (39 per cent) had an obvious deformity of the forearm, eight (10 per cent) had an inequality in the lengths of the limbs, seven (8 per cent) had an angular deformity of the knee, and two (2 per cent) had a deformity of the ankle. The average number of operations for the patients for whom the operative history was known was two.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cue search and comparison processes in visual search for letters.

In 2 experiments, each with 16 college students and laboratory staff members, Ss searched 4- and 8-letter arrays for the presence of a T or an F. The position of the target was indicated by a bar marker presented at 1 of 7 stimulus onset asynchronies (SOAs): –200, –25, 50, 125, 200, 275, or 350 msec. In Exp I, SOA conditions were blocked; in Exp II, SOA conditions varied randomly from trial to trial. In both experiments array size and SOA interacted. With 8-letter arrays, reaction time (RT) increased linearly with SOA with a slope less than 1. With 4-letter arrays, RT increased with SOA but reached asymptote at the level of no-cue control RTs at the 125-msec SOA. Results support the notion that cue search and comparison processes may function concurrently. (French summary) (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of within-dimension singleton priming in visual search.

The authors report a newly identified intertrial priming phenomenon, within-dimension singleton priming, by which search for a target that happens to be a singleton on the current trial is faster when the target on the previous trial had also been a singleton on the same dimension rather than a nonsingleton. This effect was replicated in 6 experiments with different procedures, with singletons on various dimensions, when the featural contrast defining the singleton remained the same or changed within a dimension from one trial to the next, and when the target was a singleton on a target-defining dimension or on an irrelevant dimension. These findings cannot be explained by previously demonstrated intertrial repetition effects such as dimension-specific priming or priming of popout. Theoretical implications of the within-dimension singleton priming phenomenon are discussed relative to the dimension-weighting hypothesis, the role of stimulus-driven salience in feature-guided search, and the roles of intertrial priming and goal-directed factors in visual search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Local and global orientation in visual search

Six experiments investigated the role of global (shape) and local (contour) orientation in visual search for an orientation target. Experiment 1 demonstrated that search for a conjunction of local contours with a distinct global orientation was less efficient than search for a target featurally distinct in terms of both global and local contour orientation. However, Experiments 2 and 4 demonstrated that the presence of a unique line contour was neither sufficient nor necessary to allow efficient search. Experiment 5 found that search for a local orientation difference was strongly impeded by irrelevant variation in global orientation, arguing for a preeminent role for global orientation. Finally, Experiment 6 demonstrated that the orientation search asymmetry holds for the global orientation of stimuli. Taken together, the results are consistent with visual search processes guided predominantly by a representation of global orientation.     

Age and skill in visual search.

The effects of age and experience on visual-cognitive performance were examined by administering a domain-relevant visual search task and a standard letter search task to skilled and control Ss at 2 age levels (young and middle-aged adults). In the skilled task, Ss searched for a designated item within 3-item displays using images of bacteria morphology as targets and distractors. Each target was preceded by a word prime representative of bacteria morphology that was valid, invalid, or neutral with respect to the diagnostic characteristics of the target. Skilled Ss showed an age deficit in letter search performance, but the performance of the young and middle-aged skilled Ss was not different on the domain-relevant task. Valid primes produced benefits for the young and middle-aged skilled participants, whereas control Ss were unaffected by the prime manipulation. Results were consistent with the prediction that experience serves to attenuate age-related declines in visual-cognitive performance in the skilled domain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The natural history of multiple sclerosis and its diagnosis

The treatment of multiple sclerosis (MS) is a dynamic field that is rapidly evolving. It encompasses tow main areas. The first is the direct treatment of MS itself, having evolved from using primarily steroids to the newest immunotherapies that come from the extensive research into the immune system and the role it plays in so many diseases. The second area for treatment is in the management of the effects or symptoms resulting from MS.