Chronometric analysis of apparent spotlight failure in endogenous visual orienting.

Ss made speeded responses to peripheral luminance increments or decrements preceded by informative central precues. In 4 experiments with 48 university students, one of these stimuli was much more likely to occur than the other. In a simple detection task, the likely and unlikely stimuli showed equivalent cuing effects. In a discrimination task (bright/dim), the likely stimuli showed cuing but the unlikely one did not (spotlight failure), and there was a tendency to make the likely response when the unlikely stimulus occurred at the cued location. In Exp 5, the 2 stimuli were equally likely, and a choice was required. Large cuing effects were observed for both stimuli with no evidence of a speed–accuracy trade-off. A logogen-activation framework is described within which criterion and sensitivity adjustments are needed to accommodate the full pattern of results. Endogenous orienting appears to enhance processing of all stimuli at attended (relative to unattended) locations, an effect that may be masked by specific stimulus or response expectancies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stages of auditory feature conjunction: An event-related brain potential study.

Auditory event-related brain potentials (ERPs) were recorded to tones of different frequencies and locations in a dichotic selective attention task in which Ss responded to occasional deviant tones of a prespecified location and frequency. Attention effects were isolated as negative difference (Nd) waves by subtracting ERPs to tones with no attended features from ERPs to the same tones when they shared target frequency, location, or both cues. The N1/P90 (latency 80–200 msec), originating in a tonotopically organized generator, was enhanced for all tones in the attended ear. Nd waves, beginning at 80 msec and lasting up to 700 ms, were seen to tones with either attended feature. Nd waves to frequency and location features had different scalp distributions consistent with generation in different cortical fields. Conjunction-specific Nds began 30–50 msec after Nds to individual features. The relative timing suggests that feature conjunction began before the analysis of individual features was complete. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Location-specific target expectancies in visual search.

Observers searched for local target letters in global letter configurations. Different targets appeared with different frequencies in the different locations of the configurations. Experiment 1 showed that in each location, the target that was presented there more frequently was detected faster. Experiment 2 indicated that this location-specific target probability effect was due to perceptual facilitation and that facilitation was not restricted to letters but could be generalized to nonletter stimuli. Experiments 3 and 4 showed that the location distribution of targets could be acquired for 2 global configurations concurrently and that facilitation referred to locations within the configurations, not to screen locations. The results indicate a general sensitivity of the visual system for the location of details in global configurations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The locus of location repetition latency effects.

We examined the processing locus (location vs. response) of location repetition effects in terms of the event [target (t) or distractor (d)] that initially occupied and then re-occupied the repeated location (i.e., tto- t, t-to-d, d-to-t, d-to-d). Trials were presented in pairs (prime, then probe) and 2:1 location-to-response mappings were used. Generally, for all repetition conditions, perceptual processing at the repeated location itself was facilitated (location locus), while re-activated responses delayed output production (response locus). More specifically, perceptual facilitation observed for a repeated location was independent of the kind of processing (i.e., t or d) that occurred earlier, suggesting that it is not the labeling of locations as relevant or irrelevant that determines location repetition effects. Response production was significantly slowed only when a just-inhibited response had then to be executed, which supported the view that the spatial negative priming effect has a response locus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms of visual–spatial attention: Resource allocation or uncertainty reduction?

Many studies have found that stimuli can be discriminated more accurately at attended locations than at unattended locations, and such results have typically been taken as evidence for the hypothesis that attention operates by allocating limited perceptual processing resources to attended locations. An alternative proposal, however, is that attention acts to reduce uncertainty about target location, thereby increasing accuracy by decreasing the number of noise sources. To distinguish between these alternatives, we conducted 6 spatial cuing experiments in which target location uncertainty was eliminated. Despite the absence of uncertainty, target discriminations were more accurate at the attended location, consistent with resource allocation models. These cue validity effects were observed under a broad range of conditions, including central and peripheral cuing, but were absent at very short cue–target delay intervals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The time to detect targets at inhibited and noninhibited locations: Preliminary evidence for attentional momentum.

Inhibition of return refers to the finding that response latencies are longer for targets appearing at previously attended (cued) locations than at novel (uncued) locations. The present research was designed to examine the pattern of detection latencies that occurred for targets appearing at various uncued locations. The first 2 experiments showed that responses were fastest when the target occurred at a location directly opposite the cue. Experiment 3 showed that latencies were related to the angle between the target and the direction in which attention was being oriented. Experiments 4 and 5 showed that manipulating the direction of attentional orientation affected inhibition of return. Overall, the results suggest that inhibition of return may be due to the difference between orienting attention to locations along the path of attention versus orienting attention to those off the path of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Luminance and spatial attention effects on early visual processing

Event-related potentials (ERPs) were recorded from healthy subjects in response to unilaterally flashed high and low luminance bar stimuli presented randomly to left and right field locations. Their task was to covertly and selectively attend to either the left or right stimulus locations (separate blocks) in order to detect infrequent shorter target bars of either luminance. Independent of attention, higher stimulus luminance resulted in higher ERP amplitudes for the posterior N95 (80-110 ms), occipital P1 (110-140 ms), and parietal N1 (130-180 ms). Brighter stimuli also resulted in shorter peak latency for the occipital N1 component (135-220 ms); this effect was not observed for the N1 components over parietal, central or frontal regions. Significant attention-related amplitude modulations were obtained for the occipital P1, occipital, parietal and central N1, the occipital and parietal P2, and the parietal N2 components; these components were larger to stimuli at the attended location. In contrast to the relatively short latencies of both spatial attention and luminance effects, the first interaction between luminance and spatial attention effects was observed for the P3 component to the target stimuli (350-750 ms). This suggests that interactions of spatial attention and stimulus luminance previously reported for reaction time measures may not reflect the earliest stages of sensory/perceptual processing. Differences in the way in which luminance and attention affected the occipital P1, occipital N1 and parietal N1 components suggest dissociations among these ERPs in the mechanisms of visual and attentional processing they reflect.(ABSTRACT TRUNCATED AT 250 WORDS)     

Facilitation of unattended semantic information in Alzheimer's disease: Evidence from a selective attention task.

Processing of unattended semantic information was examined in 13 patients with Alzheimer's disease (AD) and 23 normal controls (NC) using a selective attention, priming task. Two vertically aligned pictures of objects served as primes, and object names were targets. Participants were instructed to attend to only 1 picture, defined by color, in the prime display. NC participants showed facilitation only for target items that were the name of the attended prime picture, but AD patients showed facilitation from the attended and unattended prime pictures. Two accounts of these data posit a deficit in the initiation of the selection component of selective attentional processing in AD. On the basis of spotlight theories, a 3rd account posits a deficit in AD patients' ability to adjust the scope of the selection "beam." Last, facilitation of attended and unattended information may be due to crosstalk between accurately selected and unselected information. Implications of the activation of irrelevant information to language function in AD are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Localizing the development of covert attention in infants with scalp event-related potentials.

This study examined covert shifts of attention in infants aged 14, 20, and 26 weeks of age with scalp-recorded event-related potentials (ERPs). The infants were tested in a spatial cuing procedure. The reaction time (RT) to localize the target showed covert attention shifts (e.g., response facilitation or inhibition of return depending on cue–target stimulus onset asynchrony). There was a larger P1 ERP component on the valid trials than on the invalid trials or on the no-cue control trials. Presaccadic ERP potentials in response to the target were larger when it was in the cued location than when it was in uncued locations. There were increases from 14 to 26 weeks of age in the amount of inhibition of return, in the post-target-onset P1 effect. and in the presaccadic ERP potentials. These results suggest that cortical development parallels the development of covert orienting of attention and saccade planning in infants in this age range. (PsycINFO Database Record (c) 2010 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)     

Components of the location probability effect in visual search tasks.

In visual search tasks, targets are detected more rapidly when they appear in locations that commonly contain a target than when they appear in locations that rarely contain a target. Five experiments were conducted to investigate 2 specific properties of this location probability effect. In Exp I spatial location of a stimulus row was varied to determine whether high location probability facilitates target detection in a particular location in visual space or a particular relative position within the row. Both were facilitated to approximately the same extent. In Exp II an inducing target occurred with high probability in 1 of 4 display locations, and a test target occurred with equal probability in all 4 locations. Both targets were found more quickly in the high-probability location than in the other locations, but the advantage associated with targets in the high-probability location was larger for the inducing target than for the test target. In Exps III–V the correspondence between the components observed in Exps I and II was examined. The overall pattern of results was compatible with a model in which the location probability effect is produced partly by an attentional spotlight, which facilitates processing of any stimulus appearing in a particular location in visual space, and partly by a network of position-specific letter detectors, which facilitates detection of a particular letter in a particular relative position within a display. (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)     

Spatial maps of directed visual attention.

Previous studies have shown that simple reaction times (RTs) to a visual target are facilitated when the target occurs at a location expected by an observer and are slowed when the target occurs at the mirror-symmetric location contralateral to the expectancy. The present 7 experiments, with 8 observers, examined the spatial extent of this attention effect by inducing Ss to expect the target at 1 location and introducing occasional probe flashes at other locations throughout the visual field. RTs to these probes were equivalent to those obtained at the expected location so long as the probe was in the same hemifield as the S's expectancy. Conversely, RTs to probes in the hemifield opposite the expectancy generated uniformly slower response times. These results were obtained when the expected location varied in eccentricity from 2° to 16° along the horizontal meridian. In addition, when the expected and unexpected locations were within the same hemifield, no expectancy effects were observed. Under these conditions, the frequently used metaphor that directed visual attention operates like a spatially restricted "beam" appears inaccurate. Implications for current views of directed attention are considered. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flexible serial response learning by pigeons (Columba livia) and humans (Homo sapiens).

Experimental tasks designed to involve procedural memory are often rigid and unchanging, despite many reasons to expect that implicit learning processes can be flexible and support considerable variability. A version of the serial response time (SRT) task was developed, in which the locations of targets were probabilistically determined. Targets appeared in locations according to both a structured sequence and a cue validity parameter, and the time to respond to each target was measured. Pigeons (Columba livia) and humans (Homo sapiens) both showed response time facilitation at the highest tested value for cue validity, and the magnitude of that facilitation gradually weakened as cue validity was decreased. Both species showed evidence that response times were largely determined by the local predictabilities of individual cue locations. In addition, humans showed some evidence that explicit knowledge of the sequence affected response times, specifically when cue validity was 100%. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Spatially diffuse inhibition affects multiple locations: A reply to Tipper, Weaver, and Watson (1996).

S. Tipper, B. Weaver, and F. Watson (see record 84-02784) suggest that J. Pratt and R. A. Abrams's (see record 1996-16290-001) failure to find inhibition of return for more than the most recently cued location was because their 2-target display did not adequately capture some of the complexity of real-world visual environments. However, Tipper et al. tested a special case because they always cued 3 out of 4 potential targets (allowing cued and uncued locations to be segregated into 2 spatial regions). The authors show that only the 1 most recently cued location will be inhibited when 2 nonadjacent targets out of 4 possible targets are cued, but both cued locations will be inhibited when they are adjacent. Also, only the 1 most recently cued location was inhibited when 3 nonadjacent targets out of 6 potential target locations were cued. Thus, in a complex environment in which several cued locations are interspersed among noncued locations, inhibition of return will occur for only the 1 most recently attended location, consistent with conclusions of Pratt and Abrams. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The gradient of spatial auditory attention in free field: an event-related potential study

Young adult subjects attended selectively to brief noise bursts delivered in free field via a horizontal array of seven loudspeakers spaced apart by 9 degrees of angle. Frequent "standard" stimuli (90%) and infrequent "target/deviant" stimuli (10%) of increased bandwidth were delivered at a fast rate in a random sequence equiprobably from each speaker. In separate runs, the subjects' task was to selectively attend to the leftmost, center, or rightmost speaker and to press a button to the infrequent "target" stimuli occurring at the designated spatial location. Behavioral detection rates and concurrently recorded event-related potentials (ERPs) indicated that auditory attention was deployed as a finely tuned gradient around the attended sound source, thus providing support for gradient models of auditory spatial attention. Furthermore, the ERP data suggested that the spatial focusing of attention was achieved in two distinct stages, with an early more broadly tuned filtering of inputs occurring over the first 80-200 msec after stimulus onset, followed by a more narrowly focused selection of attended-location deviants that began at around 250 msec and closely resembled the behavioral gradient of target detections.     

The space of an object: Object attention alters the spatial gradient in the surround.

Although object-based attention enhances perceptual processing of information appearing within the boundaries of a selected object, little is known about the consequences for information in the object's surround. The authors show that distance from an attended object's center of mass determines reaction time (RT) to targets in the surround. Of 2 targets in the surround, both equidistant from a cue, the target closer to the center of mass was detected faster. Moreover, RT was shown to be a linear function of distance from the center of mass of a fixed, attended object, and changes to the shape of the object and its center of mass predictably altered RT. Object-based attention leads to a pattern of facilitation in the surround that may contribute to the organization of visual scenes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Meaning and modality: Influences of context, semantic memory organization, and perceptual predictability on picture processing.

Using event-related potentials (ERPs), the authors investigated the influences of sentence context, semantic memory organization, and perceptual predictability on picture processing. Participants read pairs of highly or weakly constraining sentences that ended with (a) the expected item, (b) an unexpected item from the expected semantic category, or (c) an unexpected item from an unexpected category. Pictures were unfamiliar in Exp 1 but preexposed in Exp 2. ERPs to pictures reflected both contextual fit and memory organization, as do ERPs to words in the same contexts (K. D. Federmeier and M. Kutas, see record 1999-15076-002). However, different response patterns were observed to pictures than to words. Some of these arose from perceptual predictability differences, whereas others seem to reflect true modality-based differences in semantic feature activation. Although words and pictures may share semantic memory, the authors' results show that semantic processing is not amodal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The attentional white bear phenomenon: The mandatory allocation of attention to expected distractor locations.

The authors devised a prestimulus-probe method to assess the allocation of attention as a function of participants' top-down expectancies concerning distractor and target locations. Participants performed the flanker task, and distractor locations remained fixed. On some trials, instead of the flanker display, either 2 simultaneous dots or a horizontal line appeared. The dot in the expected distractor location was perceived to occur before the dot in the expected empty location, and the line appeared to extend from the expected distractor location to the expected empty location, suggesting that attention is allocated to expected distractor locations prior to stimulus onset. The authors propose that a process-all mechanism guides attention to expected locations of all stimuli regardless of task demands and that this constitutes a major cause for failures of selective attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Target location probability effects in visual search: An effect of sequential dependencies.

Target location probability was manipulated in a visual search task. When the target was twice as likely to appear on 1 side of the display as the other, manual button-press response times were faster (Experiment 1A) and first saccades were more frequently directed (Experiment 1B) to the more probable locations. When the target appeared with equal probability at each location in this search task, performance benefited from repetition of target location in the preceding trials (Experiment 2). When the trial sequence was constrained so that target location did not repeat within a series of 4 trials, there was no longer an advantage for more probable locations (Experiment 3). The authors conclude that the search benefits for more probable locations resulted from short-term target location repetitions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)