Selective attention to global and local information: Effects of visual angle,exposure duration,and eccentricity on processing dominance

Abstract

The size and exposure duration of stimuli have been found to be relevant factors to the issue of processing dominance. Nevertheless, the relation between these two factors and their possible effects on processing dominance have never been studied. The aim of the present research was twofold: (a) to examine whether size and the exposure duration of stimuli affect processing dominance; (b) to examine whether these effects depend on the same/different eccentricity of global and local levels. Stimuli were presented at three exposure durations: 140 msec, 70 msec, and 40 msec. The overall sizes of stimuli were varied at three levels: small (3[ddot]), intermediate (6[ddot]) and large (12[ddot]). In Experiment 1 stimuli were used whose global and local levels were at different eccentricity (Hs and Ss stimuli). In Experiment 2 stimuli whose global and local levels were at the same eccentricity (Cs stimuli) were used. The results showed that the effects of visual angle on processing dominance are independent of the exposure duration of stimuli used. The transition from global to local dominance as visual angle is increased depends on the eccentricity of global and local information: It only appears when the eccentricity is different and biased towards the local level (Hs and Ss stimuli). Finally, the size of the effect is modulated by the visual angle subtended by the stimuli: the size of the effect of global advantage was inversely related to visual angle. The size of the interference effect from the local level to the global level was directly related to the visual angle, whereas that from the global level to the local level was inversely related to the visual angle subtended by the stimuli.     

The distortion of spatial relationships between local elements in hierarchical patterns decreases the global advantage effect

The present study examined the influence of perceptual organization on the processing of global and local information in hierarchical patterns. In two experiments, we examined whether disturbing the spatial relationships between local elements by introducing between-element distance and size heterogeneity affected global processing dominance. The effects on global processing dominance of undistorted compound stimuli with equidistant and homogeneous local elements were compared with those of compound stimuli which presented between-element distance heterogeneity (Experiment 1) or heterogeneity in size (Experiment 2). The results showed that the global advantage effect decreased similarly under conditions of between-element distance and size heterogeneity that disturbed the spatial relationships between local elements. The results provide new evidence on the role of perceptual organization in hierarchical patterns processing.     

Attention level and negative priming in hierarchical patterns1

Abstract: This study explored object processing associated with attention level dependent on task, using a paradigm of negative priming. Participants were required to identify target characters that appeared at either the global or local level in hierarchically structured patterns. Two experiments were conducted to examine how the global and local characters were processed in the attended and unattended levels. In the results of Experiment 1, where stimuli were presented for 10 ms, negative priming was observed in a local‐directed task, but not in a global‐directed one. These results suggested that the inhibition of local characters in the unattended level did not occur during global attention. The results of Experiment 2 revealed that negative priming was observed in both global‐ and local‐directed tasks in the 500 ms presentation, showing that inhibition in the unattended level occurred. As a result, the exposure duration influences inhibition in the unattended, especially the local level. At short exposure duration, the local characters are not inhibited when one directs attention to the global characters, whereas these are inhibited at long exposure duration.     

Global and local processing in nonattended objects: a failure to induce local processing dominance.

Paquet and Merikle (1988) found that subjects can ignore the category of unattended local forms but not that of global forms. Does this finding reflect a priority for global information during perception? In 5 studies, 2 compound stimuli, each surrounded by a frame, were presented side by side, and attention was directed to 1 of the stimuli. The first 2 studies examined whether local dominance would emerge if a small gap (Experiment 1) or the presence of small white lines (Experiment 2) on the surrounding frame specified the target object. No evidence for local dominance was found. Three additional studies examined whether local dominance would be obtained if subjects had extensive practice identifying the local aspect of stimulus displays. Although local practice led to automatic detection of unattended local targets, it did not affect the processing of the global aspect. These results are proposed to exemplify the priority of global information during perception.     

Effect of short and long exposure duration and dual-tasking on a global-local task

Past research has demonstrated a global advantage in responses to visually presented hierarchical stimuli such that, on incongruent trials, the global form interferes with responses to the local level [Kimchi, R. (1992). Primacy of wholistic processing and global/local paradigm: A critical review. Psychological Bulletin, 112, 24-38]. In Experiment 1, 32 adults performed alternating blocks of global or local identification of hierarchical letter stimuli in which the global and local letters were congruent, incongruent, or neutral, and were presented at either a short (17 ms) or long (100 ms) exposure duration. A global advantage was demonstrated at both durations. In the local-directed task, interference on incongruent, relative to neutral, trials was observed at both exposure durations, but facilitation on congruent trials, relative to neutral trials, was present only when stimuli were presented at the long exposure duration. In Experiment 2, global or local identification was performed by another group of 24 adults at either a long or short exposure duration, and also under conditions of full attention (FA) or dual-task (DT) conditions with a digit-monitoring task. Under FA, we again found significant interference at both exposure durations, but facilitation only at the long exposure duration. Under DT conditions, the pattern of facilitation and interference at the short duration remained unchanged. At the long duration, however, dual-tasking eliminated interference in the RT but not error data, while facilitation was present in both sets of data. Results are in line with a perceptual account of the global advantage, and suggest that facilitation requires consciously-mediated processes, whereas interference does not.     

Attention switching between global and local elements: Distractor category and the level repetition effect

When selecting information at global and local levels of hierarchical stimuli, there is a robust effect of level repetition in which performance is more efficient when a target is presented at the same level as the previous target. Moreover, the effect is symmetrical; it affects global and local processing equally. Evidence exists to suggest the effect may be automatic; however, we show here that the level repetition effect requires some amount of competition from the ignored level, and that the nature of the irrelevant information can determine whether the level-repetition effect is symmetrical (global and local responses are affected equally) or asymmetrical (global responses are more greatly affected than local responses). In Experiment 1, the level-repetition effect was eliminated when information at the distracting level was invariant across trials; effects of hemisphere bias and level repetition were observed only when suppression or filtering of distractor information was required. Experiment 2 demonstrated that simple featural variance is sufficient to produce the level repetition effect and that the symmetry of the level-repetition effect is sensitive to Garner-type interference that affects global processing to a greater extent than local processing. In Experiment 3, we showed that the absence of a level-repetition effect in the invariant distractor condition persists when the position of relevant stimuli is random within a block, a manipulation which should greatly reduce the contribution of controlled attention. We conclude that simple featural variance at the ignored level is critical to produce the advantage of level repetition, and that the size of the effect can be asymmetrical.     

The global precedence effect is not affected in inhibition of return

This study assessed whether inhibitory processes occurring in IOR affect perceptual processing of hierarchically organised stimuli. Experiment 1 used a global/local task that presented stimuli to the left or the right side. Results showed a global task advantage and a larger interference in the local than in the global task—the global precedence effect (GPE). These effects were larger than in previous studies using centrally presented stimuli, which suggests a greater involvement of low spatial frequency analysis with peripheral than with central stimuli. Experiment 2 combined the global/local task with IOR. Results replicated those of Experiment 1 but there was no interaction with stimulus location. That is, the GPE was not affected in IOR. Thus, we conclude that the GPE and inhibitory processing occurring in IOR are subserved by different mechanisms.     

Processing dominance of global and local information in visual patterns

The processing dominance of global and local levels of visual patterns was studied using two tasks: speeded classification and identification. Stimuli were presented with spatial certainty and controlled eccentricity. The results with both procedures showed global advantage: RTs to global level were faster than those to local level. In the same way, the interference effect was bidirectional between the global and local levels, the amount of interference being larger from the global level to the local one than vice versa.     

Low-frequency filtering and the processing of local-global stimuli

The role of low-spatial-frequency information in the processing of global stimuli made up of local elements was examined. After selective removal of low spatial frequencies two major changes occurred in the pattern of results. First, response times to global stimuli were significantly slower and the usual speed advantage of global over local processing was lost. Second, when processing local features the usual decrease in response speed when the local and global letters are not the same (consistency effect) was not obtained. These effects could not be explained by changes in error rate, by contrast variation resulting from the process of filtering, or by loss of visual sensitivity due to greater eccentricity of global images.     

Do the global advantage and interference effects covary?

The global precedence hypothesis has been operationally defined as a faster or earlier processing of the global than of the local properties of an image (global advantage) and as interference by processing at the global level with processing at the local level (global interference). Navon (1977) proposed an association between the global advantage and interference effects. Other studies have shown a dissociation between the two effects (e.g., Lamb & Robertson, 1988). It seems that the controversy in previous research resulted from not equalizing the eccentricities of global and local properties. In the present study, the eccentricities of the two levels were equalized by using stimuli with all their elements located along their perimeters. The results of the first experiment demonstrated that although the global level was identified faster than the local level in both the central and the peripheral locations of the visual field (global advantage), the pattern of global interference varied across the visual field. Consistency of global and local levels increased the speed of processing of the local level displayed at the center of the visual field but slowed down the processing of that level at peripheral locations. The results of Experiment 2 demonstrated that it was most likely that the variation in the pattern of global interference was determined by the variable of eccentricity, rather than by the sizes of the global and local levels.     

大脑两半球与整体和局部性质的选择性加工

研究大脑两半球在加工整体和局部性质中的优势以及两半球能否同时分别选择两个复合刺激的整体和局部性质。实验中把一个复合字母随机呈现在左视野或右视野,或者把两个复合字母同时分别呈现在左视野和右视野。实验一发现,在单侧呈现条件下,被试检测左右视野的整体或局部靶目标的反应时没有显著差别,但在双侧同时呈现条件下,检测右视野局部靶目标比检测左视野局部靶目标时的反应时短。实验二要求被试检测同时呈现在左右视野的整体或局部靶目标,发现当两个视野的靶目标处于同一水平时(整体或局部)反应时较短,两个视野的靶目标处于不同水平时(一侧处于整体水平而另一侧处于局部水平)反应时较长。这些结果提示,当两个复合刺激同时呈现在左右视野时,大脑左半球在选择性加工局部性质时具有优势;左右两半球更容易选择两个复合刺激同一个水平的性质,分别选择两个复合刺激不同水平的性质比较困难。     

Revisiting the global-dominance phenomenon outside the focus of attention

Previous research has demonstrated global dominance for attended and unattended stimuli. In this paper, this phenomenon is shown to be restricted to small compound stimuli. As a first step, local dominance was obtained with large (8 deg in height) attended stimuli when a single stimulus was displayed. Next, dominance in attended and unattended stimuli was investigated by displaying two large compound stimuli, one surrounded by a square (attended compound stimulus), the other one enclosed in a circle (unattended compound stimulus). The way attention was directed to the attended stimulus was varied. No dominance was observed when subjects were instructed to process the stimulus appearing in the square (experiment 2). However, when a rapid-onset cue pre-directed attention to the attended stimulus, local dominance emerged for attended, but not for unattended stimuli (experiment 3). This latter result was obtained whether or not subjects were more experienced at local than global processing (experiment 4). The implications of the results for the locus of processing dominance are discussed.     

Attention allocation modulates the processing of hierarchical visual patterns: a comparative analysis of capuchin monkeys (Cebus apella) and humans

Humans show a global advantage when processing hierarchical visual patterns, and they detect the global level of stimulus structure more accurately and faster than the local level in several stimulus contexts. By contrast, capuchins (Cebus apella) and other monkey species show a strong local advantage. A key factor which, if manipulated, could cause an inversion of this effect in monkeys is still to be found. In this study, we examined whether it was possible to induce attention allocation to global and local levels of perceptual analysis in capuchin monkeys and if by doing so, their local dominance could be reversed. We manipulated attentional bias using a matching-to-sample (MTS) task where the proportion of trials requiring global and local processing varied between conditions. The monkeys were compared with humans tested with the same paradigm. Monkeys showed a local advantage in the local bias condition but a global advantage in the global bias condition. The role of attention in processing was confined to the local trials in a first phase of testing but extended to both local and global trials in the course of task practice. Humans exhibited an overall global dominance and an effect of attentional bias on the speed of processing of the global and local level of the stimuli. These results indicate a role for attention in the processing of hierarchical stimuli in monkeys and are discussed in relation to the extent to which they can explain the differences between capuchin monkeys and humans observed in this and other studies.     

Individual differences in infant fixation duration: Dominance of global versus local stimulus properties

In three experiments, the dominance of global versus local visual properties was investigated in 4-month-old infants as a function of individual differences in fixation duration (i.e., “long-” versus “short-looking” infants). Dominance was assessed through paired-comparison discrimination tasks in which global and local visual properties were placed in competition with one another for infants' attention. Familiarization time was varied parametrically across experiments. Short-looking infants showed responses consistent with a global-to-local sequence of processing: dominance for the global attribute was supplanted by dominance for the local attribute as familiarization was extended. Long-looking infants, however, did not show dominance for either visual property until after considerable familiarization. When dominance was observed for this group, it was for the local visual attribute. These findings are in accord with previous observations that long-looking infants process visual information more slowly than short-looking infants, but further suggest that there may be qualitative differences in the manner in which the two groups of infants attend to the properties of visual stimuli. Links between this finding and the long-term predictive validity of fixation duration are discussed.     

视听刺激突显性对视觉主导效应的影响

本研究使用空间任务-转换范式,控制视、听刺激的突显性,探讨自下而上注意对视觉主导效应的影响。结果表明视、听刺激突显性显著地影响视觉主导效应,实验一中当听觉刺激为高突显性时,视觉主导效应显著减弱。实验二中当听觉刺激为高突显性并且视觉刺激为低突显性时,视觉主导效应进一步减弱但依然存在。结果支持偏向竞争理论,在跨通道视听交互过程中视觉刺激更具突显性,在多感觉整合过程中更具加工优势。     

Parallel and competitive processes in hierarchical analysis: perceptual grouping and encoding of closure.

The role of perceptual grouping and the encoding of closure of local elements in the processing of hierarchical patterns was studied. Experiments 1 and 2 showed a global advantage over the local level for 2 tasks involving the discrimination of orientation and closure, but there was a local advantage for the closure discrimination task relative to the orientation discrimination task. Experiment 3 showed a local precedence effect for the closure discrimination task when local element grouping was weakened by embedding the stimuli from Experiment 1 in a background made up of cross patterns. Experiments 4A and 4B found that dissimilarity of closure between the local elements of hierarchical stimuli and the background figures could facilitate the grouping of closed local elements and enhanced the perception of global structure. Experiment 5 showed that the advantage for detecting the closure of local elements in hierarchical analysis also held under divided- and selective-attention conditions. Results are consistent with the idea that grouping between local elements takes place in parallel and competes with the computation of closure of local elements in determining the selection between global and local levels of hierarchical patterns for response.     

Segmentation and selection contribute to local processing in hierarchical analysis.

The present study examined the role of segmentation and selection processes when we respond to local elements in hierarchical stimuli. The ease of segmentation and selection of an individual local element from hierarchical patterns was manipulated by making one local element substantially distinct from the others in colour. Experiment 1 showed that, when attention was spread across the global and local levels in a divided attention task, the introduction of the local red element speeded responses to local targets but slowed responses when targets appeared at the global level. Experiment 2 used a selective attention task in which subjects responded only to the local or the global shapes across a block of trials. Under these circumstances, the local red element reduced global-to-local interference in addition to speeding local responses. The results suggest that the efficiency with which local elements are segmented and selected affects responses to local aspects of hierarchical patterns; furthermore, the effect of local pop-out on global processing is contingent on top-down attentional control settings.     

Processing global information in briefly presented pictures

Summary The effect on object recognition of the processing of the global information in contextually coherent scenes was investigated in two experiments. In Experiment 1 subjects saw 100 ms presentations of line drawings containing objects that were either usual or unusual given the picture context. Following each exposure they were required to select from among four objects the one that had been contained in the scene. The consistency of the three distractor alternatives with the meaning of the picture was varied. Recognition accuracy was poor for unusual objects and when the distractors were consistent with the picture meaning and did not substantially differ from the performance of subjects who selected response alternatives after being provided with a theme of the picture, without actually viewing the pictures. This supports the conclusion that subjects were responding on the basis of the global information but not the local object information in the pictures. When the exposure duration was increased to 2 s (Experiment 2), processing of local information was apparent for both usual and unusual objects but effects of the global information were still evident.     

Effects of processing style on responsiveness to affective stimuli and processing fluency

In the present study, we provide direct evidence for effects of global versus local processing on responsiveness to and reliance on affective information in judgement and decision-making. Results of Experiments 1 and 2 showed an increased responsiveness to affective stimuli among participants in a global processing mode. Experiment 3 showed similar effects for processing fluency; participants adopting a global processing style showed an increased reliance on fluency. Experiment 4 replicated our findings in a more mundane judgement task in which participants judged apartments. We discuss our findings in relation to the distinction between intuitive versus deliberative modes of thinking.     

Effects of prime-target spatial separation and attentional deployment on masked repetition priming

In two masked repetition priming experiments with letter stimuli, the positions of prime and target stimuli were varied horizontally from fixation. Priming effects did not interact with position when prime and target location covaried (Experiment 1A) but diminished with increasing prime eccentricity when targets were always centrally located (Experiment 1B). Two accounts of this pattern of priming effects were proposed that postulate two different mechanisms over and above effects of visual acuity. The integration account postulates degree of separation of prime and target stimuli as the critical factor, and the attentional account postulates spatial attention as the critical factor. The results of Experiment 2, in which prime and target positions were manipulated orthogonally, were in favor of the attentional account. Repetition priming did not vary as a function of whether or not primes and targets appeared at the same location, but target processing was facilitated independently of priming when targets appeared at the same location as primes, especially in the right visual field.