Accuracy of target detection in new-object and old-object displays.

In 4 experiments, the authors investigated accuracy of detecting a target among nontargets. In some experiments, the target was a second-order square of stationary lines on a background of downward-moving lines, and nontargets were second-order squares of upward-moving lines. In other experiments, target and nontarget squares and background were shades of gray. The principal comparison was between "new" and "old" object displays. In new-object displays, search items appeared abruptly and one might be a target. In old-object displays, search items appeared abruptly, and after a delay one might become a target. Search displays in both conditions terminated shortly after target onset. Except when target onset was associated with the sole luminance change in a display, targets were much better detected in new-than in old-object displays. It is suggested that object onsets elicit a brief stimulus-driven enhancement of attention to the new objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Display density influences visual search for conjunctions of movement and orientation.

J. Driver and P. McLeod (1992) reported that the ease of visual search for targets defined by a conjunction of movement and orientation was affected by an interaction between target movement and target-nontarget discriminability. When the orientation discrimination to distinguish target from nontarget was difficult, stationary targets were easier to find than moving targets. But when the orientation discrimination to distinguish target from nontarget was easy, moving targets were easier to find than stationary targets. H. J. Muller and J. Maxwell (1994) repeated the experiment but failed to find the interaction. The authors show that the difference between these results was due to the density of the visual displays used. With a high-density display, the authors replicate Driver and McLeod's result; with a low-density display, they replicate Muller and Maxwell's result. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

SEarch via Recursive Rejection (SERR): Visual search for single and dual form-conjunction targets.

Models of visual search that assume spatially serial processing of conjunction stimuli break down when displays contain 2 identical conjunction targets: (1) They fail to account for the slopes of the target-absent reaction time (RT)/display size functions, both when the target-present response requires the detection of only 1 of the 2 targets and when it requires the detection of both targets, and (2) under redundant target conditions, the probability of "fast" present RTs is greater than that expected from the independent (serial) processing of the target stimuli. This article shows that G. W. Humphreys and H. J. Müller's (see record 1993-20216-001) parallel SERR model can account for human search performance under dual-target conditions. In SERR, simple form conjunctions are coded and grouped (on the basis of their similarity) in a spatially parallel manner, and targets are detected through the activation of a temporary "template" or through the recursive rejection of grouped distractors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

When does visual attention select all features of a distractor?

What happens after visual attention is allocated to an object? Although many theories of attention assume that all of its features are selected and processed, there has been little direct evidence that an irrelevant feature dimension of an attended nontarget is processed. In 5 experiments presented here, the authors used a singleton paradigm to investigate the effect of attention on nontarget objects. Participants made a speeded feature discrimination of a target for which the response was either compatible or incompatible with an irrelevant feature dimension of a distractor. The results show that the irrelevant distractor features were processed to the point that they interfered with the response to the target. The response compatibility effect was observed even when the location of the target or the distractor was invariant, although it was much weaker when both locations were invariant. These results demonstrate that in many circumstances, an attended distractor is completely selected and fully processed, and the complete processing of distractors depends on a number of factors, many of which are related to the strength of attention to the distractor. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Constructing Visual Representations of Natural Scenes: The Roles of Short- and Long-Term Visual Memory.

A "follow-the-dot" method was used to investigate the visual memory systems supporting accumulation of object information in natural scenes. Participants fixated a series of objects in each scene, following a dot cue from object to object. Memory for the visual form of a target object was then tested. Object memory was consistently superior for the two most recently fixated objects, a recency advantage indicating a visual short-term memory component to scene representation. In addition, objects examined earlier were remembered at rates well above chance, with no evidence of further forgetting when 10 objects intervened between target examination and test and only modest forgetting with 402 intervening objects. This robust prerecency performance indicates a visual long-term memory component to scene representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional capture of objects referred to by spoken language.

Participants saw a small number of objects in a visual display and performed a visual detection or visual-discrimination task in the context of task-irrelevant spoken distractors. In each experiment, a visual cue was presented 400 ms after the onset of a spoken word. In experiments 1 and 2, the cue was an isoluminant color change and participants generated an eye movement to the target object. In experiment 1, responses were slower when the spoken word referred to the distractor object than when it referred to the target object. In experiment 2, responses were slower when the spoken word referred to a distractor object than when it referred to an object not in the display. In experiment 3, the cue was a small shift in location of the target object and participants indicated the direction of the shift. Responses were slowest when the word referred to the distractor object, faster when the word did not have a referent, and fastest when the word referred to the target object. Taken together, the results demonstrate that referents of spoken words capture attention. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Neural evidence linking visual object enumeration and attention

Visual object enumeration is rapid and accurate for four or fewer items but slow and error-prone for over four items. This dichotomy has recently been linked to visual attentional phenomena by findings suggesting that 'subitizing' of small sets of objects is preattentive whereas 'counting' of over four items demands spatial shifts of attention. We evaluated this link at a neural level, using H2 15-O positron emission tomography to measure changes in regional cerebral blood flow while subjects enumerated the number of target vertical bars that 'popped out' of a 16-bar visual display consisting of both horizontal and vertical bars. Relative to a condition with a single target, subitizing (one to four targets) activated foci in the occipital extrastriate cortex, consistent with involvement of early, preattentive visual processes. Relative to subitizing, counting (five to eight targets) activated a widespread network of brain regions, including multiple foci implicated in shifting visual attention-large regions of the superior parietal cortex bilaterally and a focus in the right inferior frontal cortex. These results offer the first direct neural support for mapping the subitizing-counting dichotomy onto separable processes mediating preattentive vision and shifts of visual attention.     

Visual marking and change blindness: Moving occluders and transient masks neutralize shape changes to ignored objects.

Visual search efficiency improves by presenting (previewing) one set of distractors before the target and remaining distractor items (D. G. Watson & G. W. Humphreys, 1997). Previous work has shown that this preview benefit is abolished if the old items change their shape when the new items are added (e.g., D. G. Watson & G. W. Humphreys, 2002). Here we present 5 experiments that examined whether such object changes are still effective in recapturing attention if the changes occur while the previewed objects are occluded or masked. Overall, the findings suggest that masking transients are effective in preventing both object changes and the presentation of new objects from capturing attention in time-based visual search conditions. The findings are discussed in relation to theories of change blindness, new object capture, and the ecological properties of time-based visual selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ease of processing constrains the activation flow in the conceptual-lexical system during speech planning.

In 3 picture–word interference experiments, speakers named a target object in the presence of an unrelated not-to-be-named context object. Distractor words, which were phonologically related or unrelated to the context object's name, were used to determine whether the context object had become phonologically activated. All objects had high frequency names, and the ease of processing of these objects was manipulated by a visual degradation technique. In Experiment 1, both objects were nondegraded; in Experiment 2, both objects were degraded; and in Experiment 3, either the target object or the context object was degraded. Distractor words, which were phonologically related to the context objects, interfered with the naming response when both objects were nondegraded, indicating that the context objects had become phonologically coactivated. The effect vanished when both objects were degraded, when only the context object was degraded, and when only the target object was degraded. These data demonstrate that the amount of available processing resources constrains the forward cascading of activation in the conceptual-lexical system. Context objects are likely to become phonologically coactivated if they are easily retrieved and if prioritized target processing leaves sufficient resources. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Age and the selectivity of visual information processing.

Two experiments assessed age differences in the selectivity of visual information processing. Selectivity was measured by the amount of interference caused by nontarget letters when Ss detected a target letter in a visual display. In both experiments, young and elderly groups participated in search and nonsearch conditions; in the search condition, targets appeared anywhere in the display, whereas in the nonsearch condition targets were confined to the center position of the display. In Exp I, 20 19–27 yr olds and 20 65–90 yr olds were assigned to either condition for 2 sessions of testing. In Exp II, 16 young (mean age 19.8 yrs) and 16 elderly (mean age 71.8 yrs) Ss participated in both conditions. In both experiments, nontargets produced larger interference effects for old compared to young Ss in the search condition but not in the nonsearch condition. The obtained pattern of age effects could not be explained by age-related reductions in parafoveal acuity. Findings indicate that the magnitude of divided-attention deficit increases with age, whereas focused-attention deficits are unaffected by aging. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object-position binding in visual memory for natural scenes and object arrays.

Nine experiments examined the means by which visual memory for individual objects is structured into a larger representation of a scene. Participants viewed images of natural scenes or object arrays in a change detection task requiring memory for the visual form of a single target object. In the test image, 2 properties of the stimulus were independently manipulated: the position of the target object and the spatial properties of the larger scene or array context. Memory performance was higher when the target object position remained the same from study to test. This same-position advantage was reduced or eliminated following contextual changes that disrupted the relative spatial relationships among contextual objects (context deletion, scrambling, and binding change) but was preserved following contextual change that did not disrupt relative spatial relationships (translation). Thus, episodic scene representations are formed through the binding of objects to scene locations, and object position is defined relative to a larger spatial representation coding the relative locations of contextual objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceiving spatially inseparable objects: Evidence for feature-based object selection not mediated by location.

In 4 experiments, stimulus elements were arranged into an LED-like array, and letters were defined within the array by feature similarity between the elements with respect to color and form. These stimuli allowed the display of a target and a distractor letter simultaneously at the same location. They were spatially inseparable but could be separated in feature space. Participants had to identify the letter on a prespecified feature dimension (color or form). As a result, the distractors produced specific compatibility effects. This showed that nontarget features could not be ignored at an early stage (i.e., that color and form were processed automatically and in parallel up to a high stage). The target was selected from the resulting objects according to the prespecified feature dimension. Results demonstrate that object selection is possible without selecting absolute spatial arrays. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Set size, novelty, and visual pop-out in infancy.

The effects of set size and novelty on visual pop-out in 6-month-old infants was assessed in a perceptual-identification (memory reactivation) paradigm in which infants, trained and tested in their own homes, viewed a mobile containing a unique novel or familiar object amidst different numbers of familiar or novel distractors, respectively. Unique objects of both types popped out at all set sizes except the largest, where there was modest evidence that familiar distractors speeded processing (Experiment 1). When the proportion of familiar targets in a display of intermediate set size was increased, however, infants no longer detected the familiar target (Experiment 2). These findings offer additional support for the proposition that visual pop-out in infants and adults is the same phenomenon. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Shifts of visual attention to multiple simultaneous location cues.

Conducted 2 experiments to examine the effects of adjacent double cueing on target identification response times (Exp 1) and to determine whether similar results would be obtained with nonadjacent double cueing (Exp 2). For 14 observers, single and simultaneous multiple location cues were presented a brief period of time before the onset of targets that they were required to identify. Single and multiple cueing effects were similar, even when targets were presented at locations "in between" pairs of cues. The increase in response times that occurred when a target was presented at uncued locations in between a pair of cued locations suggests that pairs of cued locations are encoded independently by an operation called spatial indexing. A multiple indexing proposal and its role in mediating visual attention shifts initiated by direct cueing is described. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of background information on object identification.

Previous research using briefly presented displays has indicated that objects in a coherent scene are easier to identify than are objects in incoherent backgrounds. Of interest is whether the identification of the target object depends on the identification of the scene or the identification of other diagnostic objects in the scene. Experiment 1 indicated objects are more difficult to identify when located in an "episodically" inconsistent background even when the same diagnostic objects are present in both inconsistent and consistent backgrounds. Experiment 2 demonstrated that the degree to which noncued (cohort) objects are consistent with the target object has no effect on this object identification task. Experiment 3 showed consistent episodic background information facilitated object identification and inconsistent episodic background information did not interfere relative to "nonsense" backgrounds roughly equated on visual characteristics. Implications for models of scene perception are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in shifting focused attention.

Young and older adults performed a choice response task in which 1 of 2 target letters was presented visually at 1 of 4 display locations. In 2 experiments, the validity of a target location cue and the presence of nontarget characters (distractors) were varied. With target-only displays and 40% cue validity (Experiment 1), the estimated time to shift attention between display locations was essentially 0 msec for both age groups. With 70% cue validity, Experiment 2 demonstrated significant increases in the attention shift time as a function of both increased age and the presence of distractors (asterisks). The results suggest that age-related changes in the shifting of focused attention are minimal except when the processing of nontarget information is required. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Accurate visual memory for previously attended objects in natural scenes.

The nature of the information retained from previously fixated (and hence attended) objects in natural scenes was investigated. In a saccade-contingent change paradigm, participants successfully detected type and token changes (Experiment 1) or token and rotation changes (Experiment 2) to a target object when the object had been previously attended but was no longer within the focus of attention when the change occurred. In addition, participants demonstrated accurate type-, token-, and orientation-discrimination performance on subsequent long-term memory tests (Experiments 1 and 2) and during online perceptual processing of a scene (Experiment 3). These data suggest that relatively detailed visual information is retained in memory from previously attended objects in natural scenes. A model of scene perception and long-term memory is proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The use of visuomotor cues as a strategy for making perceptual judgments in a patient with visual form agnosia.

Accumulating evidence from human neuropsychological studies and from electrophysiological and behavioral work in the monkey is consistent with a recent proposal by M. A. Goodale and A. D. Milner (see record 1992-22553-001) that visual perception of the world is mediated by a ventral stream of visual processing projecting from striate to inferotemporal cortex whereas the visual control of skilled actions is mediated by a dorsal stream of visual processing projecting from striate to posterior parietal cortex. Compelling support for this view comes from work with a patient with visual form agnosia (DF), who cannot reliably report the size, orientation, and shape of different objects, yet can use this information to make accurate hand movements toward these same objects (for review see A. D. Milner & M. A. Goodale, 1995). Data demonstrate that DF is better able to discriminate between a square and a rectangle when she is required to reach out and pick up the designated target object than when she is required to verbally report the target's left/right position. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Saccade target selection and object recognition: evidence for a common attentional mechanism

The spatial interaction of visual attention and saccadic eye movements was investigated in a dual-task paradigm that required a target-directed saccade in combination with a letter discrimination task. Subjects had to saccade to locations within horizontal letter strings left and right of a central fixation cross. The performance in discriminating between the symbols "E" and "E", presented tachistoscopically before the saccade within the surrounding distractors was taken as a measure of visual attention. The data show that visual discrimination is best when discrimination stimulus and saccade target refer to the same object; discrimination at neighboring items is close to chance level. Also, it is not possible, in spite of prior knowledge of discrimination target position, to direct attention to the discrimination target while saccading to a spatially close saccade target. The data strongly argue for an obligatory and selective coupling of saccade programming and visual attention to one common target object. The results favor a model in which a single attentional mechanism selects objects for perceptual processing and recognition, and also provides the information necessary for motor action.     

Working memory enhances visual perception: Evidence from signal detection analysis.

We show that perceptual sensitivity to visual stimuli can be modulated by matches between the contents of working memory (WM) and stimuli in the visual field. Observers were presented with an object cue (to hold in WM or to merely attend) and subsequently had to identify a brief target presented within a colored shape. The cue could be re-presented in the display, where it surrounded either the target (on valid trials) or a distractor (on invalid trials). Perceptual identification of the target, as indexed by A′, was enhanced on valid relative to invalid trials but only when the cue was kept in WM. There was minimal effect of the cue when it was merely attended and not kept in WM. Verbal cues were as effective as visual cues at modulating perceptual identification, and the effects were independent of the effects of target saliency. Matches to the contents of WM influenced perceptual sensitivity even under conditions that minimized competition for selecting the target. WM cues were also effective when targets were less likely to fall in a repeated WM stimulus than in other stimuli in the search display. There were no effects of WM on decisional criteria, in contrast to sensitivity. The findings suggest that reentrant feedback from WM can affect early stages of perceptual processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)