"Lesioning a connectionist model of visual search: Selective effects on distractor grouping": Erratum.

Reports an error in the original article by G. W. Humphreys et al (Canadian Journal of Psychology, 1992, Vol 46, 417–460). The figures in the article were printed in the wrong order. Figures 2 and 6 should be interchanged, as should Figures 3 and 5. (The following abstract of this article originally appeared in record 1993-24303-001.) Presents a connectionist model of visual search, Search via Recursive Rejection (SERR) by G. W. Humphreys and H. J. Muller (in press), in which search is determined by patterns of grouping between distractors and between simple form elements. The performance of SERR is examined after it is subject to various types of "lesion.' Lesioning is produced either by increasing the internal noise on the activation functions governing the interactions between processing units or by eliminating processing units from different loci in SERR. Simulations demonstrate that (1) search processes can be disrupted by adding internal noise to search functions, (2) there can be selective effects on grouping processes, and (3) these selective effects can be associated with different types of lesion to different stages in SERR. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preemption effects in visual search: Evidence for low-level grouping.

Experiments are presented showing that visual search for Mueller-Lyer stimuli is based on complete configurations rather than component segments. Segments easily detected in isolation were difficult to detect when embedded in a configuration, indicating preemption by low-level groups. This preemption--which caused stimulus components to become inaccessible to rapid search--was an all-or-nothing effect and so could serve as a powerful test of grouping. It is shown that these effects are unlikely to be due to blurring by simple spatial filters at early visual levels. It is proposed instead that they are due to more sophisticated processes that rapidly bind contour fragments into spatially extended assemblies. These results support the view that rapid visual search cannot access the primitive elements formed at the earliest stages of visual processing; rather, it can access only higher level, more ecologically relevant structures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Probing distractor inhibition in visual search: Inhibition of return.

The role of inhibition of return (IOR) in serial visual search was reinvestigated using R. Klein's (1988) paradigm of a search task followed by a probe-detection task. Probes were presented at either the location of a potentially inhibited search distractor or an empty location. No evidence of IOR was obtained when the search objects were removed after the search-task response. But when the search objects remained on, a pattern of effects similar to Klein's results emerged. However, when just the search-critical object parts were removed or when participants received immediate error feedback to prevent rechecking of the search objects, IOR effects were observed only when probes appeared equally likely at search array and empty locations. These results support the operation of object-based IOR in serial visual search, with IOR demonstrable only when rechecking is prevented (facilitating task switching) and monitoring for probes is not biased toward search objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age differences in visual search: Target and distractor learning.

Age differences in a semantic category visual search task were investigated to determine whether the age effects were due to target learning deficits, distractor learning deficits, or a combination thereof. 12 young (mean age 20 yrs) and 12 older adults (mean age 70 yrs) received 2,400 trials each in consistent and varied versions of the search task. Following training, a series of transfer–reversal manipulations allowed the assessment of target learning and distractor learning both in isolation and in combination. The pattern of data suggests that older adults have a deficit in their ability to increase the attention–attraction strength of targets and to decrease the attention–attraction strength of distractors. The results are interpreted in terms of a strength-based framework of visual search performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional capture by a salient distractor in visual search: The effect of target-distractor similarity.

Models of attentional selection are based on either stimulus-driven or goal-directed processes. Support for the latter comes from a study showing that a salient singleton in a search display can be ignored when the target has a different defining feature (Kumada, 1999). We show that this finding holds only when the target and the nonsalient distractors are highly dissimilar from one another. When the target and the distractors are made more similar, whilst ensuring that the target still pops out of the display, the salient distractor can no longer be ignored. This outcome is consistent with predictions from stimulus-driven accounts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in the use of distractor homogeneity during visual search.

Previous research has suggested that an age-related decline may exist in the ability to inhibit distracting information during visual search. The present experiments used a conjunction search task in which the within-item features of the target (an upright L) and the distractors (rotated Ls) were identical. In each of 2 experiments, both young and older adults searched the display significantly more rapidly when the distractors were all rotated in the same direction (homogeneous) than when the distractors were rotated in different directions (heterogeneous). The concept of a generalized, age-related slowing was able to account for many aspects of the data, although the degree of relative improvement associated with distractor homogeneity was greater for young adults than for older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Luminance and edge information in grouping: A study using visual search.

Preattentive grouping is supported by 2 systems, a brightness system that is contrast polarity sensitive and an edge system that is relatively insensitive to contrast polarity. Search was spatially parallel for pairs of same contrast polarity vertically aligned circles, among horizontal pairs, and serial for pairs of circles that had the opposite contrast polarity (Experiments 1–3). By replacing the circles with squares, the authors investigated the effect of adding collinear edge information. When collinear edges were present, the polarity difference between paired items did not disrupt grouping (Experiments 4–6). These results support models of grouping in which brightness and edge information are processed separately (e.g., S. Grossberg & E. Mingolla, 1985) and models of visual search in which complex relations between stimuli can be computed in parallel across the display. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The effects of target and distractor familiarity on visual search in de novo Parkinson's disease patients: Latent inhibition and novel pop-out.

De novo Parkinson's disease (PD) patients identified presence or absence of a unique shape presented with homogeneous distractors. Response time (RT) was examined as a function of prior experience with target and/or distractor assessing latent inhibition (LI; slower RTs to a target that was formerly a distractor against a background of distractors that were formerly targets as compared with a novel target with distractors that were formerly targets) and novel pop-out effects. PD patients were slower than controls in detecting test-phase targets compared with preexposure-phase targets. Female PD patients with right-side motor symptoms had elevated LI compared with female controls and female PD patients with left-side symptoms. Male PD patients with right-side symptoms did not exhibit LI. Results are discussed in terms of the dopamine hypothesis and the reciprocal relationship between PD and schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age differences in visual search for compound patterns: Long- versus short-range grouping.

Visual search for compound patterns was examined in observers aged 6, 8, 10, and 22 years. The main question was whether age-related improvement in search rate (response time slope over number of items) was different for patterns defined by short- versus long-range spatial relations. Perceptual access to each type of relation was varied by using elements of same contrast (easy to access) or mixed contrast (hard to access). The results showed large improvements with age in search rate for long-range targets; search rate for short-range targets was fairly constant across age. This pattern held regardless of whether perceptual access to a target was easy or hard, supporting the hypothesis that different processes are involved in perceptual grouping at these two levels. The results also point to important links between ontogenic and microgenic change in perception (H. Werner, 1948, 1957). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Transient structures": the effects of practice and distractor grouping on within-dimension conjunction searches

It has been stated that whereas between-dimension (color x orientation) conjunctions can be searched in a "parallel" fashion, within-dimension (color x color) conjunctions are necessarily searched in a "serial self-terminating" fashion (Wolfe et al., 1990). We explored the effects of practice (within 1-h experimental session) and distractor grouping on within-dimension conjunction search tasks. In Experiments 1 and 3, the stimuli were rectangles formed by two adjacent squares; in Experiment 2, the stimuli were plus signs formed by two segments and an intersection. In Experiments 1 and 2, observers were assigned to one of two experimental conditions: In one, all the distractors shared a simple feature (the color blue); in the other, distractors did not share that simple feature. In the first condition, search became more efficient with practice and observers' performance was characterized by a shallow reaction time (RT) x set size slope; in the second condition, observers' performance did not improve as much with practice. We propose that the differential effects of practice between these two experimental conditions can be explained in terms of distractor grouping induced by the shared color of the distractors. Experiment 3 showed that, with practice, a shallow RT x set size slope characterized observers' search for a color x color target among four different distractors that shared a common color. The present results contradict a main tenet of some current visual search models--namely, that within-dimension conjunctions cannot be searched in parallel, and question the validity of using RT x set size slope functions to distinguish between preattentive versus attentive search.     

Selective attention and visual search: Revision of an allocation model and application to age differences.

Examined in 3 experiments a revised version of the Eriksen and Yeh (C. W. Eriksen and Y.-Y. Yeh, 1985) model of attentional allocation during visual search. Results confirmed the assumption of the model that performance represents a weighted combination of focused- and distributed-attention trials, although Ss relied on focused attention more than was predicted. Consistent with the model, predictions on the basis of the assumption of a terminating search fit the data better than predictions on the basis of an exhaustive search. The effects of varying cue validity favored an interpretation of focused attention in terms of a processing gradient rather than a zoom lens. Although the allocation of attention across trials was similar for young and older adults, there was an age-related increase in the time required to allocate attention within individual trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Segmentation on the basis of linear and local rotational motion: Motion grouping in visual search.

In 5 experiments using visual search procedures, grouping based on common motion was investigated. Experiments 1-3 showed that items rotating locally about their center points could be segmented and selectively searched for among stationary distractors but not among distractors rotating in the opposite direction. Experiment 4 replicated previous findings showing that upward-moving items could be selectively searched for among stationary or downward-moving items. Experiment 5 showed that rotating items could be selected efficiently from among translating items and vice versa. It is suggested that the visual system groups moving items only if they can feasibly belong to a single unique surface. Implications for current theories of visual attention are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heterogeneity effects in visual search predicted from the group scanning model.

The group scanning model of feature integration theory suggests that Ss search visual displays serially by groups, but process items within each group in parallel. Group size is determined by the discriminability of the targets in the background of distractors. When the target is poorly discriminable, the size of the scanned group will be small, and search will be slow. The model predicts that group size will be smallest when targets of an intermediate value on a perceptual dimension are presented in a heterogeneous background of distractors that have higher and lower values on the same dimension. Experiment 1 (30 Ss) demonstrates this effect; Exp 2 (12 Ss) controls for a possible confound of decision complexity in Exp 1. For simple feature targets, the group scanning model provides a good account of the visual search process. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Category effects in temporal visual search.

When subjects identify a target during rapid serial visual presentation (RSVP), they show a reduced ability to detect a subsequent probe stimulus relative to when they ignore the target. The present study demonstrated an effect of target/probe categorical relation upon this probe detection deficit (attentional blink). Experiment 1 used letters for both target and probe, replicating the general methods and results of Raymond, Shapiro, and Arnell (1992). Experiment 2 varied target/probe categorical relation via instructional set: The target was referred to as the letter 'oh', whereas for other subjects it was referred to as the number 'zero.' Treating O as a number attenuated the probe detection deficit. This different-category attenuation was confirmed in Experiment 3 where the target was a letter and the probe was a number. The observed category effect suggests that the probe detection deficit in RSVP may map a time course from spreading intra-category inhibition following temporal target selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dynamic prototypicality effects in visual search.

In recent studies, researchers have discovered a larger neural activation for stimuli that are more extreme exemplars of their stimulus class, compared with stimuli that are more prototypical. This has been shown for faces as well as for familiar and novel shape classes. We used a visual search task to look for a behavioral correlate of these findings regarding both simple geometrical shapes and more complex, novel shape classes. The latter stimulus set enabled us to control for the physical properties of the shapes, establishing that the effects are solely due to the positions of the particular stimuli in a particular shape space (i.e., more extreme versus more central in shape space) and not to specific shape features. The results indicate that finding an atypical instance of a shape class among more prototypical ones is easier and faster than the other way around. The prototypical status of a shape in our experiment could change very quickly, that is, within minutes, depending on the subset of shapes that was shown to the participants. Manipulating the degree of familiarity toward the shapes by selectively increasing familiarity for the extreme shapes did not influence our results. In general, we show that the prototypical status of a stimulus in visual search is a highly dynamic property, depending on the distribution of stimuli within a shape space but not on familiarity with the prototype. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Orientation congruency effects in visual search.

Studied 24 undergraduates who searched for the letter E in a background of letter Ls and Fs in displays that had 1, 2, 4, 8, or 12 letters. The letters could be shown at 1 of 6 orientations. The displays were either congruent for orientation or incongruent. Search time increased linearly with the number of letters in the display, and more so for E-absent trials than for E-present trials. Letter orientation, in general, increased search time and produced an M-shaped function. Results demonstrate systematic orientation effects on the time to search for a simple pattern embedded in simple backgrounds. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of target–distractor relationships in guiding attention and the eyes in visual search.

Current models of visual search assume that visual attention can be guided by tuning attention toward specific feature values (e.g., particular size, color) or by inhibiting the features of the irrelevant nontargets. The present study demonstrates that attention and eye movements can also be guided by a relational specification of how the target differs from the irrelevant distractors (e.g., larger, redder, darker). Guidance by the relational properties of the target governed intertrial priming effects and capture by irrelevant distractors. First, intertrial switch costs occurred only upon reversals of the coarse relationship between target and nontargets, but they did not occur when the target and nontarget features changed such that the relation remained the same. Second, irrelevant distractors captured most strongly when they differed in the correct direction from all other items—despite the fact that they were less similar to the target. This suggests that priming and contingent capture, which have previously been regarded as prime evidence for feature-based selection, are really due to a relational selection mechanism. Here I propose a new relational vector account of guidance, which holds promise to synthesize a wide range of different findings that have previously been attributed to different mechanisms of visual search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Guided search: An alternative to the feature integration model for visual search.

Subjects searched sets of items for targets defined by conjunctions of color and form, color and orientation, or color and size. Set size was varied and reaction times (RTs) were measured. For many unpracticed subjects, the slopes of the resulting RT?×?Set Size functions are too shallow to be consistent with A. Treisman's (see record 1988-00255-001) and A. Treisman and G. Gelade's (see record 1980-04680-001) feature integration model, which proposes serial, self-terminating search for conjunctions. Searches for triple conjunctions (Color?×?Size?×?Form) are easier than searches for standard conjunctions and can be independent of set size. A guided search model similar to J. E. Hoffman's (see record 1981-04707-001) two-stage model can account for these data. In the model, parallel processes use information about simple features to guide attention in the search for conjunctions. Triple conjunctions are found more efficiently than standard conjunctions because three parallel processes can guide attention more effectively than two. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus repetition effects on texture-based visual search by pigeons.

Four experiments investigated the effects of within-session stimulus repetition on texture discrimination. Six pigeons (Columba livia) searched for a contrasting target region (color or shape) randomly embedded within a larger distractor region for food reinforcement. Experiment 1 found that repeating features of the distractors, but not those of the target, across trials increased the accuracy of target localization relative to baseline. Experiment 2 found that subsequently switching the identity of a repeated distractor feature to the target decreased accuracy. Experiment 3 found that the effects of repeating a distractor feature influenced search performance for at least 60 trials after this learning. Experiment 4 found that differential stimulus-outcome relations can produce control by repeated target features. The results are discussed in terms of the factors and strategies involved in the control of avian visual search behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Word recall in schizophrenia: a connectionist model

OBJECTIVE: The authors examined word recall of patients with schizophrenia by using an experimental paradigm generated from connectionist models of memory. METHOD: Schizophrenic patients and normal comparison subjects first studied and then recalled a list of 32 words of equal difficulty. Both the connectivity (associative strength) and the network size (number of associates) of the words varied in such a way that the list contained equal proportions of four types of words: 1) high connectivity-small network size, 2) low connectivity-small network size, 3) high connectivity-large network size, and 4) low connectivity-large network size. RESULTS: The schizophrenic patients recalled fewer words and showed a particularly pronounced effect of the connectivity of the to-be-remembered words. For the patients, regardless of network size, recall improved substantially for words of high connectivity and declined dramatically for words of low connectivity. By contrast, the comparison subjects showed the expected effects, with the best recall for words of high connectivity-small network size, followed by words of low connectivity-small network size, then by words of high connectivity-large network size, and finally by words of low connectivity-large network size. CONCLUSIONS: Schizophrenia may be characterized by faulty modulation of associative links within a putative lexicon that is thought to be widely distributed across frontal and temporal lobes.