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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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.     

Acquisition and transfer of visual texture discriminations by pigeons.

Two experiments investigated texture discrimination in pigeons. In a simultaneous conditional-discrimination procedure, pigeons were reinforced for pecking at a small target region of identically colored form elements embedded in a larger region of distractor elements. These regions differed in either color or shape or differed redundantly in both dimensions. Pigeons readily acquired these discriminations and showed substantial positive discrimination transfer to new displays composed from novel recombinations of training colors and shapes, novel colors and shapes, and novel spatial organizations. The global organization of these displays appeared to be chief property mediating performance. This suggests that pigeons have mechanisms for perceptually grouping regions of similar colors and shapes, and these mechanisms may be similar to the preattentive visual mechanisms proposed for human texture segregation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Uniform connectedness and grouping in the perceptual organization of hierarchical patterns

The principle of uniform connectedness (S. E. Palmer & I. Rock, 1994) states that connected regions of uniform visual properties correspond to the entry-level units of visual stimuli. The implications of this principle for the perceptual organization of hierarchical patterns were investigated in 3 experiments. Primed matching and visual search were used to examine the microgenesis of organization for patterns that vary in number and relative size of their elements. Results for the few-element patterns showed an initial representation of elements with a weaker representation of global configuration. Grouping of elements into global configuration consolidated with time and involved focused attention. The entry-level units of many-element patterns were global configuration and texture. Individuation of elements occurred later and involved focused attention. These findings are discussed with reference to processes underlying perceptual organization.     

Integrating information from separable psychological dimensions.

This article examines decision processes in the perception and categorization of stimuli composed of the separable psychological dimensions, orientation and size. The randomization technique (F. G. Ashby and R. Gott; see record 1989-07388-001) of general recognition theory, which allows accurate estimation of a subject's decision boundary in a categorization task, is used in 4 experiments. Even though the stimulus components are clearly separable, it was found that Ss were not constrained to use separable response strategies, nor were they constrained to attend to distance to the prototypes. Instead, they used decision rules that were nearly optimal, even if this required information integration or for the Ss to attend to higher level category properties such as component correlation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention to orientation, size, luminance, and color: Attentional failure within the form domain.

Whether Ss can attend to physical dimensions of objects without access to semantic information about them was examined. Ss decided which of 2 laterally presented pictures, a target and a distractor, had the same orientation (Exp 1), size (Exp 2), luminance (Exp 3), or color (Exp 4) as a reference picture. In each experiment, the matching stimuli were either physically identical, semantically related, or semantically unrelated. The reference stimulus and the distractor were either semantically related or unrelated. When matching was based on orientation or on size, performance was facilitated when the matching stimuli were semantically related, and it was disrupted when the distractor was semantically related to the reference stimulus. Semantic effects were eliminated when matching was based on luminance or color. The results are discussed in terms of physiological data, form and surface information, and global and local processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influences of categorization on perceptual discrimination.

Four experiments investigated the influence of categorization training on perceptual discrimination. Ss were trained according to 1 of 4 different categorization regimes. Subsequent to category learning, Ss performed a Same–Different judgment task. Ss' sensitivities (d's) for discriminating between items that varied on category-(ir)relevant dimensions were measured. Evidence for acquired distinctiveness (increased perceptual sensitivity for items that are categorized differently) was obtained. One case of acquired equivalence (decreased perceptual sensitivity for items that are categorized together) was found for separable, but not integral, dimensions. Acquired equivalence within a categorization-relevant dimension was never found for either integral or separable dimensions. The relevance of the results for theories of perceptual learning, dimensional attention, categorical perception, and categorization are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Frames of reference and distinctive figural characteristics affect shape perception.

In 4 experiments it was found that global frameworks and local distinctive figural characteristics influenced the perception of shape and of pointing. In Exps 1 and 2, Ss were asked to mark the center of the middle figure in array of 3 aligned figures (either triangles or squares). Displacements of the center indicated a perceived deformation of the shapes. In Exp 3, Ss were asked to adjust the height of triangles in arrays similar to those in Exp 1. Height adjustments made along the axis of apparent pointing resulted in extents that were shorter than the height necessary to form equilateral triangles. In Exp 4, stimuli were isosceles triangles in which the apparent distortion had been nulled; however, Ss continued to perceive them as pointing in a direction consistent with their alignment, and hence shape distortion cannot be the cause of pointing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Probability learning on incidentally observed dimensions: A response bias effect.

Performed 2 experiments with 140 university students which demonstrate the occurrence of response bias effects as a function of previous probability learning and which are independent of stimulus dimensions. In Exp I, Ss first received training predicting the alternatives on a brightness dimension of metric patterns on a 70-30 probability distribution with the incidental dimensions of symmetry and concentration varying independently either on 70-30 or 50-50 distributions. After 200 trials, Ss were shifted to an incidental dimension; they predicted dimension alternatives on the incidental dimensions at a rate higher than appropriate controls Ss with no prior training. Exp II demonstrated that the response bias effect was dependent on the nature of the prior probability training. Ss first predicted on a 70-30 distribution of shape and were shifted to either a 70-30 or 50-50 distribution of nonsense syllables. Comparisons with nontraining control groups showed that Ss with prior training predicted the nonsense syllable alternatives at a higher rate. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention, similarity, and the identification–categorization relationship.

A unified quantitative approach to modeling Ss' identification and categorization of multidimensional perceptual stimuli is proposed and tested. Two Ss identified and categorized the same set of perceptually confusable stimuli varying on separable dimensions. The identification data were modeled using R. N. Shepard's (see record 1959-05134-001) multidimensional scaling-choice framework, which was then extended to model the Ss' categorization performance. The categorization model, which generalizes the context theory of classification developed by D. L. Medin and M. M. Schaffer (see record 1979-12633-001), assumes that Ss store category exemplars in memory. Classification decisions are based on the similarity of stimuli to the stored exemplars. It is assumed that the same multidimensional perceptual representation underlies performance in both the identification and categorization paradigms. However, because of the influence of selective attention, similarity relationships change systematically across the 2 paradigms. Findings provide some support for the hypothesis that Ss distribute attention among component dimensions so as to optimize categorization performance and that Ss may have augmented their category representations with inferred exemplars. Results demonstrate that excellent predictions of categorization performance can be made given knowledge of performance in an identification paradigm. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Location dominance in attending to color and shape.

Investigated in 4 experiments whether Ss direct attention to stimulus location when attempting to attend to its color or shape. In the 1st 2 experiments, a given property (location, color, or shape) of a letter cue instructed Ss whether to report any letters from a subsequent display. Regardless of which property was relevant, Ss reported letters adjacent to the cue and not those similar to its color or shape. In the last 2 experiments, the varied location of a cue was irrelevant to the task, whereas its varied color instructed Ss to report a letter in a given location or of a given shape. Targets adjacent to the cue were reported faster than those remote from the cue. The results suggest that attempting to attend to any aspect of a stimulus entails directing attention to location. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Complex decision rules in categorization: Contrasting novice and experienced performance.

The ability of novice and experienced Ss to learn complex decision rules was tested with 3 categorization tasks. Each task involved 2 categories with exemplars that were normally distributed on 2 stimulus dimensions. Three separate sets of stimuli were used, and in each task the decision rule that maximized categorization accuracy was a highly nonlinear function of the stimulus dimension values. In the 3 tasks, all experienced Ss used highly nonlinear decision rules. Quadratic rules were supported over bilinear rules, and in many cases Ss used nearly optimal decision rules. These findings did not depend on whether the stimulus components were integral or separable. Novice Ss also did not use simple linear rules. A model that assumed Ss tried a succession of different linear rules was also rejected. Instead, novices appeared to use quadratic rules, although less consistently than experienced Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impulsivity and perception: Individual differences in the processing of the local and global dimensions of stimuli.

In Exp I, 48 undergraduates differing in impulsivity (as measured by a self-report inventory) performed 2 versions of filtering, interference, and invariant control tasks. In one version, Ss sorted according to the value of the local dimension; in the other, the global dimension was the relevant one. In addition, Ss performed a task in which the 2 dimensions were perfectly correlated. Results show that Ss sorted more quickly when the global dimension was relevant than when the local dimension was relevant. In Exp II, 43 of the Ss from Exp I were used to determine whether failure to find a relationship between impulsivity and filtering performance was due to correlations of local and global dimensions; results were negative. In Exp III, the same 43 Ss used in Exp II were used to test the information-integration hypothesis. Results support the hypothesis—high impulsives were more impaired than other Ss when the task required that they integrate information from the global dimension with information from the local dimension. Findings can be explained in terms of individual differences in the value placed on speed, relative to accuracy, in information processing. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The stimulus in information processing.

Argues that the nature of the stimulus is an important variable determining how information is processed. 2 major stimulus concepts are discussed: dimensional integrality vs. separability, and state vs. process limited stimuli. These concepts relate to the effects of stimulus redundancy on discrimination. There will be a gain with redundancy: (a) if the need for redundancy is due to a process limitation and the redundant dimensions are integral, or (b) if the need for redundancy is due to state limitation and the redundant dimensions are separable. Redundancy can also lead to improvement in discrimination if the stimulus elements can be integrated into a gestalt whole. (28 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selection and implementation of strategies in reasoning by analogy.

160 undergraduates were either trained to solve analogies using 1 of 3 different strategies or not given strategy training. Half of the Ss received analogies with integral attributes, and half received analogies with separable attributes. Ss were administered the Figure Analogies from the American Council on Education Psychological Examination for College Freshmen, the Abstract Reasoning from the Differential Aptitude Tests, and a questionnaire regarding their analogy-task performance. Findings indicate that (a) it was possible to train Ss to use various strategies for solving integral analogies; (b) Ss were not aware of the relative success or failure of the training; (c) Ss were aware of differences in the effectiveness of the alternative strategies, and their views were consistent with the actual differences; (d) scores on a figural series completion test were correlated with analogy solution latencies only for Ss who either were untrained or were trained to use the strategy they probably would have used if they had been untrained; (e) Ss' differential performance within content conditions on the analogy task was correlated in many instances with the Ss' metacognitive awareness of their success in strategy implementation; and (f) the preferred model used by untrained Ss was the most efficacious model and perceived to be the most efficacious one. Results show the importance of considering content variables, as well as task-execution and S variables, in the study of metacognitive and cognitive performance in information processing. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Global shape cannot be attended without object identification.

Tested whether the global shape of objects can be processed without accessing semantic or identity information. Ss judged which of 2 fragmented forms had the same global shape as a reference stimulus. Matching stimuli could be physically identical, semantically related, or unrelated. The reference stimulus and nonmatching (distractor) form could be semantically related or unrelated. Similarity effects in the related condition were unconfounded with matches nameable and nonnameable forms. For nameable forms, related matching forms facilitated performance; a related distractor disrupted performance. Semantic interference was eliminated when nameable distractors were replaced with nonnameable partners; semantic similarity effects on matching were eliminated with a nonnameable reference stimulus and with inverted targets and distractors. Access to information concerning global shape does not normally occur without object identification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interhemispheric relations in processing hierarchical patterns: Evidence from normal and commissurotomized subjects.

On the basis of a review of neuropsychological evidence for several component processes of responding to global and local levels of hierarchically structured patterns, L. C. Robertson and M. R. Lamb (see record 1991-24938-001) hypothesized that interhemispheric communication between posterior cortexes would disrupt the typically interfering effects of global patterns on local response. These studies confirmed this hypothesis in 3 commissurotomized Ss. The normal interaction between visual field presentation and global or local level was present in normal Ss and all 3 patients, but global interference was absent or even reversed in patients. These data are discussed as they relate to the function of the corpus callosum and functional hemisphere asymmetries in responding to global and local levels of hierarchical forms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Global and local processing in humans (Homo sapiens) and chimpanzees (Pan troglodytes): Use of a visual search task with compound stimuli.

This research assessed the visual processing of the global and local stimulus features in humans and chimpanzees. In Experiment 1, participants were tested with compound stimuli presented in a visual search task. There was an advantage to process the global stimulus level in humans but not in chimpanzees. The global size and the density of the local elements were manipulated in Experiment 2. Humans showed an overall advantage for processing the global shape. Chimpanzees showed an advantage for processing the local shape in the low-density condition but showed no advantage in the dense conditions. In Experiment 3, chimpanzees showed a global advantage when line segments connected the local elements and a local one when the lines were removed. Together, these results suggest a phylogenetic trend in the way compound stimuli are processed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Convergent validation of information processing constructs with Pavlovian methodology.

These two experiments introduce a new nonverbal measure of stimulus structure by merging Garner's (1974) distinction of separable and integral stimulus properties with the field of Pavlovian conditioning. According to one rule, two sets of stimuli (separable vs. integral) were constructed. In each experiment a differential compound conditioning procedure was used with one group of subjects who were trained with a subset of the separable material and then were tested with an unfamiliar subset. The same procedure was used with a second group but with integral materials. Both experiments showed a reversal of conditioning effects, depending on the properties of the stimuli. Separable compounds showed results as predicted by elementaristic 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)