Hemispheric processing of global form, local form, and texture.

Hemispheric processing of global form, local form, and texture of hierarchical patterns composed of many, relatively small elements and patterns composed of few, relatively large elements was examined in two experiments, employing a Stroop-type paradigm. In experiment 1 subjects were instructed to attend either to the global or the local level of the pattern and to identify the form at the designated level. In experiment 2 subjects were to identify the global form or the texture. A right visual field (left hemisphere) advantage was obtained for detection of local form, and a left visual field (right hemisphere) advantage was obtained for detection of global form. When many-element patterns were processed in terms of global form and texture, the results failed to show reliable hemispheric differences. The results suggest that the hemispheres differ in their sensitivity to the relatively more global versus the relatively more local aspects of visual patterns which require focused attention (as in global/local form detection). When the task involved distributed attention (as in texture detection) no lateralized effects were observed.     

Effects of good form and spatial frequency on global precedence

Does the global precedence effect depend on the goodness of the global form and low spatial frequencies? In Experiments 1 and 2, under a variety of attentional and task conditions, a global advantage in response time (RT) occurred in “good,” many-element compound patterns but not in “poor,” few-element patterns (unless the local elements were too small to be easily recognized). Symmetric interference effects were found in all patterns, however, suggesting that global and local information were encoded in parallel and that the global advantage in RT involved some postperceptual processes. Experiments 3A and 3B showed that the global advantage in RT and perceived pattern goodness depend on low spatial frequencies: Lowpass-filtered patterns rated as “good” showed the usual global advantage in RT, but highpass-filtered, many-element forms rated as “poor” did not. These findings suggest that a global advantage in RT requires an unambiguous global form conveyed by low spatial frequencies.     

The effect of category learning on the representation of shape: dimensions can be biased but not differentiated

Recent studies have suggested a profound influence of category learning on visual perception, resulting in independent processing of previously integral dimensions. The authors reinvestigate this issue for shape dimensions. They first extend previous findings that some shape dimensions (aspect ratio and curvature) are processed in a separable way, whereas others (radial frequency components) are not. They then show that a category-learning phase improved the discrimination of a relevant with respect to an irrelevant dimension, but only for separable dimensions. No similar effect was found on the relative sensitivity for integral shape dimensions. Thus, category learning is capable of biasing separable shape dimensions but does not alter the status of dimensions in the visual system as either separable or integral.     

Microgenesis and ontogenesis of perceptual organization: evidence from global and local processing of hierarchical patterns

In two experiments, visual search and speeded classification were used to study perception of hierarchical patterns among participants aged 5 to 23 years. Perception of global configurations of few-element patterns and local elements of many-element patterns showed large age-related improvements. Only minor age-related changes were observed in perception of global configurations of many-element patterns and local elements of few-element patterns. These results are consistent with prior microgenetic analyses using hierarchical patterns. On the one hand, the rapid and effortless grouping of many small elements and the individuation of few large elements both mature by age 5. In contrast, the time-consuming and effortful grouping of few large elements and the individuation of many small elements improve substantially with age, primarily between ages 5 and 10. These findings support the view that perceptual organization involves multiple processes that vary in time course, attentional demands, and developmental trajectories.     

Children's perceptual organisation of hierarchical visual patterns

Abstract

Children's perceptual organisation of hierarchical patterns was investigated in two experiments through similarity judgements. Previous studies with adults demonstrated that the perceptual relations between the global configuration and the local elements of such patterns depend critically on the number of elements embedded in the pattern: Patterns composed of a few, relatively large elements are perceived in terms of global form and figural parts, whereas patterns composed of many relatively small elements are perceived in terms of global form and texture. In Experiment 1 children at three levels of age (preschoolers, first and third graders) were presented with a standard figure and two comparison figures—a proportional and an un proportional enlargement of the standard. The number of elements in the standard figure was varied. When the number of elements was small, children at all age levels concerned judged the proportional enlargement which preserves the global and local forms as well as the relationship between them as more similar. When the number of elements in the standard figure increased, children switched their preference to the un proportional enlargement which preserves both the global form and the textural properties of the standard figure. When the global configuration and the local elements were pitted against each other (Experiment 2), and the number of elements was rather large, preschoolers and third graders judged the comparison figure having the same global configuration as the standard but composed of different elements as more similar to the standard than the comparison figure having the same elements arranged in a different configuration. Overall, these results are similar to the ones obtained with adults: As far as the perceptual organisation of hierarchical patterns changes as a function of the number of elements for the adult perceiver, it changes also for the young child. These results do not support the hypothesis that young children perceive complex visual stimuli as undifferentiated wholes, as some develop mental researchers have proposed. Furthermore, the finding that for children, as for adults, the elements do not function perceptually as parts when the number of elements is large, implies that fewclement patterns are better candidates for testing hypotheses about the relative priority of wholes and parts across development.     

A feature-integration theory of attention

A new hypothesis about the role of focused attention is proposed. The feature-integration theory of attention suggests that attention must be directed serially to each stimulus in a display whenever conjunctions of more than one separable feature are needed to characterize or distinguish the possible objects presented. A number of predictions were tested in a variety of paradigms including visual search, texture segregation, identification and localization, and using both separable dimensions (shape and color) and local elements or parts of figures (lines, curves, etc. in letters) as the features to be integrated into complex wholes. The results were in general consistent with the hypothesis. They offer a new set of criteria for distinguishing separable from integral features and a new rationale for predicting which tasks will show attention limits and which will not.     

Processing of global and local information in memory

The experiments reported in this paper were designed to test how global and local information are processed by the memory system. When subjects are required to match a given letter with either a previously presented large capital letter or the small capital letters comprising it, (1) responses to the global level (i.e. the big letter) are faster than responses to the local level (i.e. the small letters), and (2) responses to the latter level only are affected by the consistency between the large and the small letters (Experiment 2), a pattern similar to that obtained in perception (Experiment 1). Such results obtain when subjects are required to attend to only one level with a short ISI between the first and second stimulus, but not when a longer ISI is used (Experiment 5) or when subjects are required to attend to both levels at the same time (Experiments 3 and 4). The results are discussed in the light of a model that postulates a temporal precedence of the global information over the local one at the perceptual level.     

The separability of space and time: Dimensional interaction in the memory trace

The speeded-classification paradigm, adapted from the study of perceptual interactions, was used to examine interactions among features of the short-term memory trace. In each of four experiments, a trial began with the presentation of a pair of stimuli, each member of which occurred either first or second in time and above or below a fixation point. One of the two stimuli was then presented again, and the task was to classify its prior temporal (Experiments 1 and 3) or spatial (Experiments 2 and 4) position. The main question of interest asked whether subjects could selectively attend to one of these occurrence dimensions while ignoring irrelevant variation along the other. The results suggested that whereas subjects can selectively ignore temporal or spatial variation when no recall of the irrelevant dimension’s value is required, they suffer interference when values on both dimensions must be remembered. The obtained patterns of interference are consistent withpostperceptual interactions of the-spatial and temporal components of the memory trace.     

Asymmetric interactions in the processing of the visual dimensions of position, width, and contrast of bar stimuli.

The processing of different dimensions of a single stimulus may be either integral or separable. Dimensions are called integral if correlated variation of one improves discrimination on the basis of the other and random variation of one interferes with discrimination on the basis of the other. For separable dimensions on the other hand, subjects can attend to one dimension and disregard variations in the other. These discrimination tests were used to find the interactions between the processing of the visual dimensions of position, width, and contrast of a light bar stimulus. The relations between these dimensions were found to be asymmetric: judgments of position and width are independent of contrast variations, but variations in these dimensions influence contrast discriminations. Furthermore, position variations influence width judgements more than vice versa. The data were analyzed for repetition effects, and it was found that this model is not sufficient to explain all the interaction phenomena. The asymmetries found may be related to the different ways these dimensions are mapped onto cortical neuron responses.     

The effect of prolonged viewing on the recognition of global and local levels of hierarchically constructed patterns

Two experiments were carried out to examine delays in the recognition of test patterns after prolonged (25 s) viewing of an adaptation pattern which was composed of either the same or different local components and global structures. In the case of geometric patterns that contained a few relatively large elements, there were significant delays of about 70 ms in the global decision task when the test and adaptation stimuli (TS and AS) were of the same pattern, or when they had the same structure but different components. In contrast, in the case of geometric patterns that were composed of many relatively small elements, such a figural relation between the AS and the TS did not affect the recognition speed of the TSs either in the global or in the local decision task. These results suggest that prolonged viewing reduces the efficiency of global processing and that such a disruptive effect occurs depending upon the number and the relative size of the elements that make up the whole pattern.     

Accessing similarity and dimensional relations: effects of integrality and separability on the discovery of complex concepts

A series of studies investigated how stimulus integrality and separability impact the cognitive accessibility of similarity and dimensional relations. A good deal of previous work has established that stimulus integrality and separability differentially determine perception; here, the question is whether they also have differential effects on conception. Are the principles that govern perception also principles that can be readily discovered in concept learning tasks? Is a similarity-based rule especially easy to abstract from integral stimuli and a dimensionally-based rule especially easy to abstract from separable stimuli? In Experiments 1 and 2, we measured the relative ease with which the two types of rules (similarity and dimensional) are discovered by adults with the two types of stimuli (integral and separable). In experiment 1, the two rules were made redundant and we asked which rule the subjects learned. In Experiment 2, one rule was made relevant and the other irrelevant, and we compared relative speeds of learning. The results from the studies led us to conclude (a) that dimensionally based rules are more accessible from separable than from integral stimuli; (b) that similarity-based rules are more accessible from integral than from separable stimul; and (c) that, in general, subjects have a bias to access dimensional relations in this type of task. Experiment 3 pursued an additional suggestion from Experiments 1 and 2 that the dimensional relations within integral stimuli are sometimes accessible, more so when larger interstimulus differences are encountered. In confirmation, Experiment 3 demonstrated that adult subjects are more successful in applying a dimensional rule to pairs of integral stimuli that differ by a small amount if they also have exposure to pairs of integral stimuli that differ by a large amount. In a later discussion, it was argued that such a finding is consistent with the notion that the "dimensions" of integral stimuli are merely arbitrary directions in the integral stimulus space, and some relevant pilot data to that effect were presented. Finally, Experiment 4 took up a developmental issue. Young children have sometimes produced perceptual responses governed by similarity relations when presented with stimuli that are separable for adults. Will they more readily access similarity-based or dimensionally-based relations from such stimuli in the concept learning tasks here? The results showed that both kindergarteners and fifth graders more readily access the dimensional relations. A final discussion integrated the findings from the several experiments, taking up the following issues: (a) the relation between the perception and the conception of stimulus relations and (b) the nonprimacy of the dimensional axes in the integral stimulus space.     

Perceptual integrality of sex and identity of faces: further evidence for the single-route hypothesis

According to current face-recognition models, sex (gender) and identity of faces are processed in independent routes. Using Garner's speeded-classification task, the authors provide evidence that sex and identity are processed within a single route. In 4 experiments, participants judged the sex or the familiarity of faces while the other dimension remained constant or varied randomly. The results of Experiments 1, 2, and 4 showed that participants could not selectively attend to either sex or familiarity without being influenced by the other, irrelevant dimension. Thus, identity and sex are integral dimensions. Experiment 3 provided evidence that when sex judgments are based on hairstyle heuristics, false separability can emerge. The findings support the claim that identity and sex are processed within a single route.     

Circle size and diameter tilt: A new look at integrality and separability

In six experiments using the speeded classification paradigm, we provide evidence that the ostensibly “separable” dimensions of size and orientation can produce patterns of either separability or asymmetric configurality, depending on the spatial arrangement of the stimuli. In all experiments, subjects classified large or small circles contairting a single line in one of two possible orientations. When the line touched the circle’s perimeter, thereby defining the diameter of the circle (Experiments 1–4), asymmetric configurality obtained: Variations in size interfered with classification by orientation, but variations in orientation did not interfere with classification by size, and redundancy gain was weak or absent. When the lines fell completely within (i.e., did not touch) the circles (Experiments 5 and 6), the results were consistent with separability: There was neither redundancy gain nor interference. Taken together, the results add to the growing body of evidence that classification of specific dimensional pairs as separable or integral may be less feasible than identifying the more general conditions that increase or decrease the psychological salience of dimensional structures and facilitate or interfere with selection of optimal processing strategies.     

The role of spatial-frequency channels in the perception of local and global structure

Adaptation and reaction-time techniques were used to examine the role of different spatial-frequency channels in the perception of local and global structure. Subjects were shown figures consisting of a large C composed of smaller Cs and asked to identify the orientation of either the global C or its local elements. Prior to performing the task subjects were adapted to different spatial frequencies and the effect on subsequent performance was assessed. Two main results were found. First, the adapting frequency that most affected the global task was often lower than that most affecting the local task, suggesting that high and low frequencies independently code the structure of an image. Second, reaction time to global figures was often faster than to local figures at all levels of detectability, again suggesting a role of low-frequency channels in global processing.     

Component summation or configuration in human eyelid conditioning depends upon stimulus properties

The experiment reviewed here merges Garner's (1974) distinction of separable and integral stimulus properties with the field of Pavlovian eyelid conditioning with human subjects. According to one rule, two sets of stimuli (separable vs integral) were constructed. A differential compound conditioning procedure was used with one group of subjects being trained with a subset of the separable material and then tested with a new subset. The same procedure was used with a second group but with integral material. The experiment showed a reversal of conditioning effects, depending on the properties of stimuli. Separable compounds showed results as predicted by elementistic conditioning theories: the associative values of the elements summed up. With integral compounds, the associative values of the elements were irrelevant. Instead, integral compounds were processed and classified primarily on the basis of similarity.     

Unsupervised category learning with integral-dimension stimuli

Despite the recent surge in research on unsupervised category learning, the majority of studies have focused on unconstrained tasks in which no instructions are provided about the underlying category structure. Relatively little research has focused on constrained tasks in which the goal is to learn predefined stimulus clusters in the absence of feedback. The few studies that have addressed this issue have focused almost exclusively on stimuli for which it is relatively easy to attend selectively to the component dimensions (i.e., separable dimensions). In the present study, we investigated the ability of participants to learn categories constructed from stimuli for which it is difficult, if not impossible, to attend selectively to the component dimensions (i.e., integral dimensions). The experiments demonstrate that individuals are capable of learning categories constructed from the integral dimensions of brightness and saturation, but this ability is generally limited to category structures requiring selective attention to brightness. As might be expected with integral dimensions, participants were often able to integrate brightness and saturation information in the absence of feedback—an ability not observed in previous studies with separable dimensions. Even so, there was a bias to weight brightness more heavily than saturation in the categorization process, suggesting a weak form of selective attention to brightness. These data present an important challenge for the development of models of unsupervised category learning.     

Unsupervised category learning with integral-dimension stimuli

Despite the recent surge in research on unsupervised category learning, the majority of studies have focused on unconstrained tasks in which no instructions are provided about the underlying category structure. Relatively little research has focused on constrained tasks in which the goal is to learn predefined stimulus clusters in the absence of feedback. The few studies that have addressed this issue have focused almost exclusively on stimuli for which it is relatively easy to attend selectively to the component dimensions (i.e., separable dimensions). In the present study, we investigated the ability of participants to learn categories constructed from stimuli for which it is difficult, if not impossible, to attend selectively to the component dimensions (i.e., integral dimensions). The experiments demonstrate that individuals are capable of learning categories constructed from the integral dimensions of brightness and saturation, but this ability is generally limited to category structures requiring selective attention to brightness. As might be expected with integral dimensions, participants were often able to integrate brightness and saturation information in the absence of feedback--an ability not observed in previous studies with separable dimensions. Even so, there was a bias to weight brightness more heavily than saturation in the categorization process, suggesting a weak form of selective attention to brightness. These data present an important challenge for the development of models of unsupervised category learning.     

Component summation or configuration in human eyelid conditioning depends upon stimulus properties

The experiment reviewed here merges Garner’s (1974) distinction of separable and integral stimulus properties with the field of Pavlovian eyelid conditioning with human subjects. According to one rule, two sets of stimuli (separable vs integral) were constructed. A differential compound conditioning procedure was used with one group of subjects being trained with a subset of the separable material and then tested with a new subset. The same procedure was used with a second group but with integral material. The experiment showed a reversal of conditioning effects, depending on the properties of stimuli. Separable compounds showed results as predicted by elementistic conditioning theories: the associative values of the elements summed up. With integral compounds, the associative values of the elements were irrelevant. Instead, integral compounds were processed and classified primarily on the basis of similarity.     

儿童整体-局部加工中的负启动现象

采用2种元素疏密程度的复合数字刺激和启动范式,7岁和11岁2个年龄组的小学生分别在注意整体水平和注意局部水平的条件下对探测刺激进行选择反应。结果发现元素疏密程度可以影响知觉优先,而知觉优先与整体局部水平间的负启动之间没有一致的发展关系,说明与负启动有关的注意分配机制可能比知觉组织发展的晚。     

Haptic integration of object properties: texture, hardness, and planar contour

Planar objects varying in shape, texture, and hardness were classified under haptic exploration. Classes were defined by values on one dimension, or redundantly, by two or three dimensions. Response times and exploratory procedures (Lederman & Klatzky, 1987) were recorded. Experiment 1 showed that a second dimension speeded responses for all combinations (redundancy gain), but a third dimension produced no further effect. In Experiments 2 and 3, classification trials began with two redundant dimensions, and subsequently one was withdrawn (held constant). When texture and hardness varied redundantly, withdrawal of either increased response time--even when subjects were initially instructed to focus on one dimension. Joint exploration for texture and hardness dominated whenever the two varied redundantly and persisted despite withdrawal. Redundancy gains (Experiment 1), but not substantial withdrawal effects (Experiments 2 and 3), were observed for combinations of texture or hardness with planar contour, indicating less integration than between substance dimensions. Compatibility of exploratory procedures appears to constrain dimensional integration.