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PubMed1984

Attention in the processing of complex visual displays: detecting features and their combinations.

The distinction between operations in visual processing that are parallel and preattentive and those that are serial and attentional receives both theoretical and empirical support. According to Treisman's feature-integration theory, independent features are available preattentively, but attention is required to veridically combine features into objects. Certain evidence supporting this theory is consistent with a different interpretation, which was tested in four experiments. The first experiment compared the detection of features and feature combinations while eliminating a factor that confounded earlier comparisons. The resulting priority of access to combinatorial information suggests that features and nonlocal combinations of features are not connected solely by a bottom-up hierarchical convergence. Causes of the disparity between the results of Experiment 1 and the results of previous research were investigated in three subsequent experiments. The results showed that of the two confounded factors, it was the difference in the mapping of alternatives onto responses, not the differing attentional demands of features and objects, that underlaid the results of the previous research. The present results are thus counterexamples to the feature-integration theory. Aspects of this theory are shown to be subsumed by more general principles, which are discussed in terms of attentional processes in the detection of features, objects, and stimulus alternatives.

Adult↗

PubMed1984

Shape and depth perception from parallel projections of three-dimensional motion.

Parallel projections of dots on the surface of a transparent sphere rotating about a vertical axis provide strong impressions of depth and spherical shape. The hypothesis was tested that these impressions are the result of three perceptual heuristics: (a) The sinusoidal projected velocity function of each dot in the horizontal dimension tends to be perceived as a rotary motion in depth; (b) the projected velocity gradient in the vertical dimension is perceived as curvature in depth; and (c) the simultaneously visible fields of dots moving in opposite directions are perceived as surfaces separated in depth. When each factor was varied independently, all three significantly affected judgments of spherical shape and depth. Similar results were obtained with cylinders. The first factor was more important for shape judgments; the second was generally more important for depth judgments. These results, together with those of earlier studies in which these factors led to similar effects for different stimuli and transformations, suggest that these are general principles applicable to the perception of structure from both rigid and nonrigid motion.

Depth Perception↗

PubMed1985

Automatic and attentional components in perception of shape-at-a-slant.

In perceiving shape-at-a-slant it is assumed that a sequence of operations is executed. The aim of these experiments was to determine the extent to which execution of these operations requires allocation of attention. Three hypotheses were considered: zero automaticity--that all of the operations require attention; partial automaticity--that the operations culminating in a representation of projective shape and slant-in-depth are automatic while the combinatorial operations culminating in a distally correlated shape require attention; full automaticity--that the entire sequence of operations is automatic, proceeding without allocation of attention. To decide among these hypotheses, subjects performed forced-choice shape recognition tests under two conditions: In the shape-directed condition subjects were motivated to process shape. In the numerosity-directed condition subjects were motivated to direct attention to discrimination of numerosity, thereby causing attention to be diverted from processing of shape. Examination of the pattern of choices on the recognition test showed results that conformed best to the hypothesis of partial automaticity.

Attention↗

PubMed1986

Classifying multidimensional stimuli: stimulus, task, and observer factors.

When observers decide how to classify stimuli, they often employ one of two types of information: identity along one particular dimension or overall similarity. The present studies examined interrelations among the factors which determine the use of these types of information. Participants' classifications of certain types of materials (e.g., size and brightness, length and density) revealed strong individual differences, were related to the individual's response tempo and selective processing ability, and were influenced by task demands. Classifications of other materials (e.g., saturation and brightness) did not reveal individual differences, were not affected by response tempo and selective processing ability, and were unaffected by changes in task demands. The former, but not the latter, types of materials have also been found to be influenced by developmental differences. The results are consistent with the idea that differences in response tempo and selective processing ability underlie observer differences (both individual and developmental) and that certain types of stimuli which are not susceptible to such influences set boundary conditions for observer differences. The results are discussed within an integral-to-separable model of processing.

Adult↗

PubMed1986

Does attention affect visual feature integration?

Two questions are investigated in this work: first, whether the integration of color and shape information is affected by attending to the stimulus location, and second, whether attending to a stimulus location enhances the perceptual representation of the stimulus or merely affects decision processes. In three experiments, subjects were briefly presented with colored letters. On most trials, subjects were precued to the stimulus location (valid cue); on some trials, a nonstimulus location was cued (invalid cue). Subjects were less likely to incorrectly combine colors and letter shapes following a valid cue. The attentional facilitation afforded by the cue was not limited to feature integration but also affected the registration of features. However, when the amount of feature information was strictly controlled, attention still affected feature integration. The results indicate that orienting attention to the location of the cue affects the quality of the perceptual representation for features and their integration.

Adolescent↗

PubMed1988

Tests of a temporal theory of attentional binding.

Different features of stimuli present in the field of view appear to be registered in different cortical maps. How, then, are the features that come from the same object bound together rather than mistakenly assembled with features coming from other simultaneously present objects? One theory supposes that an attentional mechanism intercepts input coming from particular retinal locations at a way station prior to parsing of the features from the same object. Any enhancement (or facilitation) at that stage will cause all the features from that object to be modified simultaneously in the downstream registers. The imposed temporal synchronicity serves as the essential binding cue. Five experiments provided no support for the theory. There is no tendency for synchronicity of features to cause binding unless the features come from the same location. Location, rather than temporal synchronicity, appears to be the essential cue for binding.

Attention↗

PubMed1989

Evidence for two types of spatial representations: hemispheric specialization for categorical and coordinate relations.

Analyses of human object recognition abilities led to the hypothesis that 2 kinds of spatial relation representations are used in human vision. Evidence for the distinction between abstract categorical spatial relation representations and specific coordinate spatial relation representations was provided in 4 experiments. These results indicate that Ss make categorical judgments--on/off, left/right, and above/below--faster when stimuli are initially presented to the left cerebral hemisphere, whereas they make evaluations of distance--in relation to 2 mm, 3 mm, or 1 in. (2.54 cm)--faster when stimuli are initially presented to the right cerebral hemisphere. In addition, there was evidence that categorical representations developed with practice.

Adult↗

PubMed1989

Ratings of kinetic depth in multidot displays.

Subjects saw kinetic depth displays whose shape (sphere or cylinder) was defined by luminous dots distributed randomly on the surface or in the volume of the object. Subjects rated perceived 3-D depth, rigidity, and coherence. Despite individual differences, all 3 ratings increased with the number of dots. Dots in the volume yielded ratings equal to or greater than surface dots. Each rating varied with 3 of 4 factors (shape, distribution, numerosity, and perspective), but the ratings either between trials or between conditions were often uncorrelated. Object shape affected rigidity but not depth ratings. Veridically perceived polar displays had slightly lower rigidity but higher depth ratings than parallel projection displays. (Reversed polar displays were always grossly nonrigid.) The interaction of ratings and stimulus parameters requires theories and experiments in which different KDE ratings are not treated interchangeably.

Attention↗

PubMed1990

Transparent layer constancy.

Perceived transparency was studied as a constancy problem. In the episcotister (E-) model of scission, luminances are partitioned into layer and background components; four luminances determine values of two layer parameters that specify constancy of a transparent layer on different backgrounds. The E-model was tested in an experiment in which 12 Ss matched 24 pairs of four-luminance patterns by adjusting two luminances of the comparison pattern. Both the standard and the comparison were perceived as a transparent layer on a checkerboard. The E-model predicts matches when layer values are identical in the two patterns. One parameter was constant, constraining the adjustment along the second dimension. Obtained values corresponded well with E-predictions. Alternative models based on local luminance or average contrast ratios accounted for less variability. Results indicate that transparency models should utilize luminance, not reflectance, as the independent variable.

Adult↗

PubMed1991

Directing spatial attention within an object: altering the functional equivalence of shape descriptions.

Three experiments extended the demonstrated effects of spatial attention to a new area, the perceptual organization of objects. We manipulated observers' fixation location, their spatial attention location, and their intentions to hold one alternative of a Necker cube that had been altered in one region to favor one of the alternative interpretations (the biased region) and measured reports about the perceived organization of the cube over 30-s trials. Regardless of fixation location, responses showed obligatory effects of the bias only when observers attended to the biased region of the cube and not when they attended to the unbiased region of the cube, even when the biased region lay between fixation and the attended unbiased region. On the basis of these experiments, we argue that spatial attention operates through mechanisms of facilitation and inhibition to determine the functional nature of the structural description of an object.

Adult↗

PubMed1991

Comparison of cube rotations around axes inclined relative to the environment or to the cube.

Observers judged whether 2 successive computer-displayed rotations of a cube were the same or different. With respect to the observers, each rotation was about a vertical axis (Y), a horizontal (line-of-sight) axis (Z), an axis tilted just 10 degrees from vertical or horizontal, or a maximally oblique axis. Independently, with respect to the cube, each rotation was about a symmetry axis through opposite faces (F) or through opposite corners (C), an axis tilted 10 degrees from one of these symmetry axes, or an axis of extreme nonsymmetry. Speed and accuracy of comparison decreased as the axes of the successive rotations departed from the canonical axes of the environment (Z, or especially, Y), or even more sharply, from the symmetry axes of the cube (C, or especially, F). The internalized principles that guide the perceptual representation of rigid motions evidently are ones of kinematic geometry more than of physics.

Attention↗

PubMed1992

Attentional demands of processing shape in three-dimensional space: evidence from visual search and precuing paradigms.

The hypothesis that representation of projective shape is preattentive whereas representation of objective shape in three-dimensional space requires allocation of attention was tested in 2 visual search and 2 precuing experiments. In the visual search experiments, the slope for projective shape search was expected to approach 0 and that for objective shape search was expected to be a positive monotonic function of set size. In the precuing experiments, the effects of precuing were expected to be largely limited to the task requiring representation of objective shape. The overall pattern of results conformed to expectations. The findings are interpreted in the context of a model of shape-at-a-slant processing set out by Epstein and Lovitts (1985) and Epstein and Babler (1989, 1990).

Adult↗

PubMed1993

Visual attention and objects: evidence for hierarchical coding of location.

In 5 experiments, it was found that judging the relative location of 2 contours was more difficult when they belonged to 2 objects rather than 1. This was observed even when the 1- and 2-object displays were physically identical, with perceptual set determining how many objects they were seen to contain. Such a 2-object cost is consistent with object-based views of attention and with a hierarchical scheme for position coding, whereby object parts are located relative to the position of their parent object. In further experiments, it was shown that in accord with this hierarchical scheme, the relative location of objects could disrupt judgments of the relative location of object parts, but the reverse did not occur. This was found even when the relative position of the parts could be judged more quickly than that of the objects.

Adult↗

PubMed1976

Allocation of attention during visual word recognition.

A dual-task paradigm was used to assess attentional processing demands during visual word recognition. By manipulating the difficulty of each task, it is argued that the procedure estimates the attention demands of the memory-access component of word recognition. Specifically, the the complexity of the secondary task was varied from a simple reaction time task to a choice reaction time task, and the difficulty of a lexical decision (word vs. nonword) primary task was varied by manipulating word frequency. A comparison of the effect of secondary task complexity across levels of word frequency showed that the difference between the two secondary tasks was larger for low-frequency words than for high-frequency words. This result, supported by other characteristics of the data, suggests that the memory-access processing in one type of word recognition task does demand attention.

Acoustic Stimulation↗

PubMed1994

Spatial attention to arrays of multidimensional objects.

Encoding briefly displayed arrays of multidimensional objects appears to require selective attention, but this hypothesis is challenged by M. J. Nissen's (1985) finding that properties of an object are reported independently. Selective attention to some objects but not others should produce positive dependence. Theoretical analysis shows that deviations from independence would have been difficult to observe in Nissen's data because of high guessing rates and small sample sizes. Four new experiments showing strong positive dependence in property reports are described. Deviations from independence were highly significant for most Ss. Quantitative modeling shows that selective attention to subsets of objects would produce about the amount of dependence obtained. Rather than challenging attention theories, the amount of dependence in encoding multidimensional objects is consistent with selective attention to either objects or locations.

Attention↗

PubMed1997

Discrimination of the direction and speed of motion in depth of a monocularly visible target from binocular information alone.

Thresholds for discriminating a monocularly visible object's direction of motion in depth and speed of motion in depth were measured using only binocular cues. Observers could discriminate the direction of motion in depth while totally ignoring speed and discriminate the speed of motion in depth while totally ignoring direction. Direction discrimination thresholds were the same for motion in depth within the vertical and horizontal meridians, even though a cue to trajectory was available for motion within the horizontal meridian that is not available for motion within the vertical meridian. Speed discrimination thresholds also were the same for motion in depth within the vertical and horizontal meridians. For the 3 observers the lowest direction discrimination thresholds were 0.14 degree, 0.18 degree, and 0.22 degree (means of horizontal and vertical thresholds).

Depth Perception↗

PubMed1998

Texture segregation and visual search: a comparison of the effects of random variations along irrelevant dimensions.

The effects of irrelevant variations in the color and depth of elements on participants' ability to detect and discriminate elements defined by a difference in orientation were compared. Consistent with previous research, it was found that there was no effect or small effects if the targets were single elements in visual search tasks and that there were large effects for targets defined by several elements defining an area in visual segmentation tasks. It is suggested that the reason for the discrepancy between the 2 paradigms lies in the need for grouping processes in segmentation experiments. This notion was examined in 3 additional experiments that manipulated grouping processes through task demands and stimulus design. The data provide tentative support for this notion.

Adult↗

PubMed2001

Inhibitory effects of repeating color and shape: inhibition of return or repetition blindness?

There is a current debate regarding whether attention is influenced by stimulus attributes other than location. The present article replicates and extends previous findings that repeating the nonspatial attribute of color leads to a delay in target detection (M. B. Law, J. Pratt, & R. A. Abrams, 1995). Repetition disadvantage effects were found for the stimulus attributes of both color and shape, as well as for location. However, the nonspatial repetition disadvantage disappeared if the stimuli were presented in peripheral locations (Experiments 3a, 3b, and 4) or the cue was presented for 50 ms (Experiment 6). Moreover, the magnitude of the repetition disadvantage tended to decline as the cue-target stimulus-onset asynchrony increased (Experiments 5a, 5b, and 6). These results suggest that a repetition blindness mechanism may underlie the repetition disadvantage effects of nonspatial features, rather than an inhibition of return mechanism.

Adolescent↗