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PubMed2002

The stereoscopic anisotropy: individual differences and underlying mechanisms.

Observers are more sensitive to variations in the depth of stereoscopic surfaces in a vertical than in a horizontal direction; however, there are large individual differences in this anisotropy. The authors measured discrimination thresholds for surfaces slanted about a vertical axis or inclined about a horizontal axis for 50 observers. Orientation and spatial frequency discrimination thresholds were also measured. For most observers, thresholds were lower for inclination than for slant and lower for orientation than for spatial frequency. There was a positive correlation between the 2 anisotropies, resulting from positive correlations between (a) orientation and inclination thresholds and (b) spatial frequency and slant thresholds. These results support the notion that surface inclination and slant perception is in part limited by the sensitivity of orientation and spatial frequency mechanisms.

Anisotropy↗

PubMed1977

Perceptual load in searching for sloping colored lines camouflaged by colored backgrounds: a separate-groups investigation.

Altogether 168 men searched briefly for colored sloping lines embedded in a background of random color. Using a separate-groups experimental design, search for six kinds of target was found to be less effective after practice than search for a single kind of target. Reducing the number of colors of targets from three to one was considerably more beneficial than reducing the number of main directions of slope from two to one. Reducing the number of kinds of target without reducing the number of relevant stimulus values was also found to improve the effectiveness of search, but search was even more effective when the number of relevant stimulus colors was reduced. The results can be predicted from the total number of selection operations required. However, a more precise fit needs to reflect the considerably greater difficulty of searching for a number of directions of slope. When targets were poorly camouflaged, search was equally effective whether there were four colors or only a single color of target to search for.

Adolescent↗

PubMed1977

Reaction times in a bisensory task: implications for attention and speech perception.

Reading reaction time (RT) to visual stimuli was shown to vary according to the nature of simultaneous auditory stimuli. In Experiment 1, simultaneous different digits produced slower RTs than a burst of speech noise, while identicaly digits produced faster RTs. In Experiments 2 and 3 the stimuli were phoneme pairs which differed on either zero, one, or two articulatory features. Identical phonemes resulted in the fastest RTs. The RTs to non-identical phoneme pairs were not directly related to the number of differing features but were dependent upon the specific feature involved. A two-stage model was proposed to explain the results in which parallel processing of simultaneous input occurs prior to a decision-making stage.

Attention↗

PubMed1978

Normalization of irrelevant dimensions in stimulus comparisons.

When subjects compared two multidimensional stimuli with respect to a single (relevant) dimension in a same-different task, variation in the irrelevant dimension systematically affected reaction times. For same trials, reaction times increased monotonically with the amount of disparity between the stimuli on the irrelevant dimension. The dimensions were heights and widths of ellipses or hues and tints of color patches. The results were interpreted in terms of a normalization process that internally transforms the irrelevant dimensions of the two stimuli until they are equal. The amount of normalization, and hence same reaction time, increased with increasing disparity on the irrelevant dimension. These results suggest that in order to decide that two objects are equivalent in some criterial respect, it is often necessary to normalize irrelevant disparities.

Color Perception↗

PubMed1979

Rotation of objects in pictures viewed at an angle: evidence for different properties of two types of pictorial space.

As an observer views a picture from different viewing angles, objects in the picture appear to change orientation relative to the observer, but some objects change orientation more than others. This difference in rotation for different objects is called the differential rotation effect. The differential rotation is not, however, accompanied by corresponding changes in the perception of the spatial layout of objects in the picture. This lack of correspondence between the perception of rotation and the perception of spatial layout is a result of the fact that the information on a picture's surface defines two kinds of pictorial space with different properties. Rotation is perceived in terms of the pictorial space outside the picture, and spatial layout is perceived in terms of the pictorial space inside the picture.

Depth Perception↗

PubMed1979

A model of unidimensional perceptual matching.

Faster same than different judgments typically are obtained when two letters are compared. When two tones that might differ only on frequency are compared, however, same judgments typically are slower than different judgments. A uniprocessor, unidimensional model, based on Krueger's noisy-operator theory, was fitted satisfactorily to data from four published studies of tone comparison. The model predicts faster response time on different judgments because of heterogeneity of difference. Because the second tone in a pair typically may be either higher or lower in frequency than the first, there will be a greater variety of perceived difference counts on different pairs than on same pairs. As a result, a large difference count will be decisive and will lead to an immediate "different" response, because it can be produced only by a different pair, whereas a small difference count will not be so decisive because it can be produced by either a same or a different pair. Consequently, there generally will be more rechecking on same than different pairs, and thus longer RT on same pairs.

Auditory Perception↗

PubMed1979

Secondary task modality, expectancy, and the measurement of attentional capacity.

Previous studies have obtained conflicting evidence regarding the effect of probe modality when a secondary probe task is used to measure attentional demands of a primary letter-matching task. The present experiments found no difference in the shape of the probe reaction time functions for auditory and visual probes as long as probe modality was known. When probes "unexpectedly" occurred in the modality that was different from the majority of the probes, differences were obtained. Only the unexpected auditory function changed, shape relative to the others, with reaction time to probes that occurred early in the matching task sequence being increased. The results are interpreted as supporting a role of attentional capacity in the activation of structures that accept relevant sensory input.

Attention↗

PubMed1980

Overcoming Stroop interference: the effects of practice on distractor potency.

With practice, do distracting stimuli lose their ability to distract? In a series of experiments, subjects practiced counting digits, a task subject to Stroop-type interference, and then were tested in a variety of transfer conditions. The results indicate that digits do lose their ability to distract as a result of practice but that this loss is highly specific; practice in ignoring one pair of distractors (2 and 4) does not improve later performance when ignoring a different pair (1 and 3). However, this practice effect does transfer to distractor stimuli having the same meaning as the stimuli ignored in practice (TWO and FOUR, but not TO and FOR). The results can be explained either in terms of active learning to suppress distraction or in terms of habituation of competing responses.

Attention↗

PubMed1980

Confirmed reservations: mental travel.

When Kosslyn, Ball, and Reiser asked subjects to scan a memorized picture, they found a strong positive linear relationship between distance scanned and reaction time. However, more recent research has suggested that this result may be as much a function of the demand characteristics of the experiment as a reflection of any structural properties of the image. To further test this possibility with complex stimuli, college subjects were either presented with Kosslyn's pictorial stimuli or verbal descriptions of same in a "nonexperiment" and were asked to predict their scanning times. The subjects were able to produce high linear correlations between scanning distance and predicted scanning time. This result is consistent with a demand characteristics explanation of the correlation between distance and reaction time that is obtained in actual image-scanning studies.

Distance Perception↗

PubMed1981

Importance of the overall similarity of objects of adults' and children's classifications.

Previous work has shown that adults and older children tend to classify multi-dimensional objects by identity on one dimension, whereas children under 8 years of age tend to classify these same objects by a relation of overall similarity. The present study investigated the hypothesis that this developmental trend is restricted to the classification of simple objects that differ only by limited amounts on a few dimensions. The specific hypothesis was that overall-similarity relations structure both adults' and children's classifications of heterogenous objects (objects that differ in a variety of ways). This hypothesis was suggested by the correspondence between the structure of young children's classifications and the structure of natural categories. The result of two experiments supported the hypothesis. When the to-be-classified objects varied simultaneously on relatively many dimensions, adults as well as children constructed classifications that maximized within-category similarity on all varying dimensions. The implications of these results for accounts of the perception of multidimensional relations and classificatory behavior are discussed.

Adult↗

PubMed1981

A positional discriminability model of linear-order judgments.

The process of judging the relative order of stimuli in a visual array was investigated in three experiments. In the basic paradigm, a linear array of six colored lines was presented briefly, and subject decided which of two target lines was the leftmost or rightmost (Experiment 1). The target lines appeared in all possible combinations of serial positions and reaction time (RT) was measured. Distance and semantic congruity effects were obtained, as well as a bowed serial position function. The RT pattern resembled that observed in comparable studies with memorized linear orderings. The serial position function was flattened when the background lines were homogeneously dissimilar to the target lines (Experiment 2). Both a distance effect and bowed serial position functions were obtained when subjects judged which of two target lines was below a black bar cue (Experiment 3). The results favored and analog positional discriminability model over a serial ends-inward scanning model. The positional discriminability model was proposed as a "core model" for the processes involved in judging relative order or magnitude in the domains of memory and perception.

Color Perception↗

PubMed1979

Stimulus similarity and order as factors in visual short-term memory in nonhuman primates.

The short-term retention of nonhuman primates for a single sample or for two successively presented samples was assessed in four delayed matching-to-sample experiments with delays of .03, 4, 8, 16, and 32 sec. The single sample tasks included one (Experiment 1) or two (Experiment 4) distractor stimuli in the choice set (matching test). In the two successive samples tasks, the animals matched (reconstructed) the order of presentation of two samples with (Experiment 3) and without (Experiment 2) a distractor stimulus. Also, the possible combinations of eight stimuli (four colors and four shapes) were arranged to test the effects of sample set and choice set similarity. Taken together, analyses of the errors indicated that both sample and choice set similarity were significant sources of confusions in delayed matching. Order errors occurred independently of similarity but were a source of forgetting primarily at the longest delays (16 and 32 sec). Two exceptions to the similarity effect (second response errors in Experiment 3 and errors of an inexperienced group in Experiment 4) were observed. Possible reasons for the exceptions and several implications of these findings for theories of short-term memory are discussed.

Animals↗

PubMed2006

The Bender-Gestalt II.

In 2003, the Bender-Gestalt II was published. In the present article, the revision process is described, and major changes to the test are discussed. These changes include additional designs, a memory (recall) phase, Motor and Perception supplementary tests, a detailed observation form, a global scoring system, and a large, nationally representative normative base. Directions for future research are also provided.

Bender-Gestalt Test↗

PubMed1990

A functional theory of the McCollough effect.

Pattern-contingent color aftereffects, or McCollough effects (MEs), are used to probe the visual brain's operations psychophysically. Their neural substrate is unknown, however, and theories about them are weak. Our theory proposes a strong functional role for MEs and a neuropsychological basis that accounts for "top-down" (global) constraints ignored by other theories. The functional aspect of the theory is based on the concept of contingent adaptation level, following Helson (1964), and on the "error-correcting device" of Andrews (1964), which tracks and adjusts internal representation to external-world contingencies. The neuropsychological part of the theory postulates that global properties are the result of MEs being generated not at the individual detector level but in vectorfields of which the detectors are elements. It is an implementation of Lie transformation group theory (Hoffman, 1966). Evidence for this model is assessed.

Brain↗

PubMed1992

Dynamic binding in a neural network for shape recognition.

Given a single view of an object, humans can readily recognize that object from other views that preserve the parts in the original view. Empirical evidence suggests that this capacity reflects the activation of a viewpoint-invariant structural description specifying the object's parts and the relations among them. This article presents a neural network that generates such a description. Structural description is made possible through a solution to the dynamic binding problem: Temporary conjunctions of attributes (parts and relations) are represented by synchronized oscillatory activity among independent units representing those attributes. Specifically, the model uses synchrony (a) to parse images into their constituent parts, (b) to bind together the attributes of a part, and (c) to bind the relations to the parts to which they apply. Because it conjoins independent units temporarily, dynamic binding allows tremendous economy of representation and permits the representation to reflect the attribute structure of the shapes represented.

Depth Perception↗

PubMed1989

Kinetic depth effect and identification of shape.

We introduce an objective shape-identification task for measuring the kinetic depth effect (KDE). A rigidly rotating surface consisting of hills and valleys on an otherwise flat ground was defined by 300 randomly positioned dots. On each trial, 1 of 53 shapes was presented; the observer's task was to identify the shape and its overall direction of rotation. Identification accuracy was an objective measure, with a low guessing base rate of the observer's perceptual ability to extract 3D structure from 2D motion via KDE. (1) Objective accuracy data were consistent with previously obtained subjective rating judgments of depth and coherence. (2) Along with motion cues, rotating real 3D dot-defined shapes inevitably produced a cue of changing dot density. By shortening dot lifetimes to control dot density, we showed that changing density was neither necessary nor sufficient to account for accuracy; motion alone sufficed. (3) Our shape task was solvable with motion cues from the 6 most relevant locations. We extracted the dots from these locations and used them in a simplified 2D direction-labeling motion task with 6 perceptually flat flow fields. Subjects' performance in the 2D and 3D tasks was equivalent, indicating that the information processing capacity of KDE is not unique. (4) Our proposed structure-from-motion algorithm for the shape task first finds relative minima and maxima of local velocity and then assigns 3D depths proportional to velocity.

Adult↗

PubMed1990

Comparable measurement scales in task-comparison experiments.

The primary goal of this comment on the article by Schacter, Cooper, and Delaney (1990) is to illustrate two kinds of advantages of comparable measurement scales for task-comparison experiments. First, a comparable metric allows quantitative comparisons of the degree of accurate performance across tasks, which yields more information than the qualitative conclusions from tests of significance on noncomparable measurement scales. Second, such a scale can highlight situations in which fundamentally different kinds of comparisons are being attempted. A few remarks about the inferences drawn from the research are also offered.

Adult↗

PubMed2006

Is the binding of visual features in working memory resource-demanding?

The episodic buffer component of working memory is assumed to play a role in the binding of features into chunks. A series of experiments compared memory for arrays of colors or shapes with memory for bound combinations of these features. Demanding concurrent verbal tasks were used to investigate the role of general attentional processes, producing load effects that were no greater on memory for feature combinations than for the features themselves. However, the binding condition was significantly less accurate with sequential rather than simultaneous presentation, especially for items earlier in the sequence. The findings are interpreted as evidence of a relatively automatic but fragile visual feature binding mechanism in working memory. Implications for the concept of an episodic buffer are discussed.

Analysis of Variance↗