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Results for “SIZE PERCEPTION”

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At least 937 records · Page 52Linked to original sources
PubMed2005

The visual computation of 2-D area by human observers.

Normal human observers compared either the width, height or area of two simultaneously-presented shapes (the standard and the test), with a cue to indicate which decision had to be made. On 'area' trials, test width was a random variable, ensuring that neither shape (aspect ratio), width nor height by themselves was a reliable signal. Weber fractions for width and height of both ellipses and rectangles were in the range 5-10%, but for area they were higher (10-20%) than predicted from the combination of noisy width and height decisions. With ellipses, observers were more likely to overestimate width or height when the other dimension differed from the standard in the same direction (e.g. both greater). We conclude that observers have no access to high-precision codes for 2-D area, and that they base their decisions on a variety of heuristics derived from 1-D codes. A second experiment measured acuity for changes in aspect ratio. For ellipses, accuracy for aspect ratio was higher than predicted by the combination of noisy width and height signals; for rectangles it was worse, suggesting that 2-D curvature is a potent cue to shape.

Cues↗
PubMed2001

Active artificial echolocation and the nonvisual perception of aperture passability.

The potential of airborne sonar to provide effective information about three-dimensional (3D) spatial layouts was assessed in four companion experiments. Blindfolded participants, never given visual access to the layout of a large room, were asked to use a sonar device whose output they had never previously encountered to judge the passability (by normal walking) of apertures between two aligned wall panels. Estimates were made from fixed and variable locations, approaches to the apertures were made from orthogonal and oblique angles, and the panels were at different distances and orientations. In each experiment, participants gave evidence of an ability to immediately use the information in structured echoes to make these judgments, though aperture location, approach angles, wall alignment and orientation each had significant effects on performance. The data are compared with performance under visual and nonechoic auditory conditions and are discussed with respect to the notions of potential information and effective information during these perceptually guided tasks.

Adult↗
PubMed1990

Judgments of proportions.

This study investigated the processes that underlie estimates of relative frequency. Ss performed 4 tasks using the same stimuli (squares containing black and white dots); they judged "percentages" of white dots, "percentages" of black dots, "ratios" of black dots to white dots, and "differences" between the number of black and white dots. Results were consistent with the theory that Ss used the instructed operations with the same scale values in all tasks. Despite the use of the correct operation, Ss consistently overestimated small proportions and underestimated large proportions. Variations in the distributions of actual proportions affected the extent to which Ss overestimated small proportions and underestimated large proportions in the direction predicted by range-frequency theory. Results suggest that proportion judgments, and by analogy probability judgments, should not be taken at face value.

Adult↗
PubMed1991

Perceiving the vertical distances of surfaces by means of a hand-held probe.

Nine experiments were conducted on the haptic capacity of people to perceive the distances of horizontal surfaces solely on the basis of mechanical stimulation resulting from contacting the surfaces with a vertically held rod. Participants touched target surfaces with rods inside a wooden cabinet and reported the perceived surface location with an indicator outside the cabinet. The target surface, rod, and the participant's hand were occluded, and the sound produced in exploration was muffled. Properties of the probe (length, mass, moment of inertia, center of mass, and shape) were manipulated, along with surface distance and the method and angle of probing. Results suggest that for the most common method of probing, namely, tapping, perceived vertical distance is specific to a particular relation among the rotational inertia of the probe, the distance of the point of contact with the surface from the probe's center of percussion, and the inclination at contact of the probe to the surface. They also suggest that the probe length and the distance probed are independently perceivable. The results were discussed in terms of information specificity versus percept-percept coupling and parallels between selective attention in haptic and visual perception.

Adult↗
PubMed1994

A dynamic theory of proportional judgment: context and judgment of length, heaviness, and roughness.

Subjects judged the length of lines, the heaviness of weights, or the roughness of sandpaper in 2 conditions. In 1 condition, they were instructed to make all their judgments relative to a long-term reference point, which consisted of a reference response and sensation. In the other condition, they were told to use a short-term reference point, namely, the response and sensation of the previous trial. A dynamic model of proportional judgment (L. T. DeCarlo, 1989/1990) predicts that the autocorrelation of successive responses will be larger for the latter instructions. This prediction was confirmed for the 3 continua. In addition, fits of a recently proposed dynamic regression model show that there is little or no effect of the previous stimulus intensity on the current response, whereas the results for an earlier model suggest a large contrast effect. The theory and experiments provide insight into judgmental and sensory processes in magnitude scaling.

Adult↗
PubMed1977

Control of attention in the processing of temporal and spatial information in complex visual patterns.

Eighteen stimuli were created by orthogonally varying the area (A), perimeter (P), and exposure duration of checkerboard patterns. Subjects judged either the area and duration of the presented shapes (area-time group) or the perimeter and duration (perimeter-time group) of the same figures. Perceived duration, area, and perimeter varied with changes in the uninstructed an the instructed stimulus dimensions. The discussion focuses on the ability of subjects to control the allocation of attention to instructed stimulus dimensions, as well as on the evidence in the data in favor of detailed sequential or fast holistic processing. It is suggested that the concept of stimulus complexity, defined as P2/A, is useful in describing the temporal and spatial illusions obtained in this study.

Attention↗
PubMed1982

Determinants of attention to local and global features of visual forms.

This article deals with the problem of how attention is distributed to different levels of detail (global, local) in visual scenes. Six experiments explore the effect of a previous level of processing on current processing. The contention that processing at a given level of detail biases the distribution of attention so that more is allocated to that level for future processing is supported by the presence in the data of a robust level-readiness effect, whereby processing is faster at a given level if previous processing has been at that level. The level-readiness effect occurs regardless of the conspicuity of features at the various levels. Conflict between levels seems to depend on the imbalance of conspicuity and attention allocation between levels, with the more conspicuous or attended-to-level interfering more. A model of two-state attention switching similar to that of Sperling and Melchnor (1978) is proposed to explain these data. the final experiment confirmed the somewhat unusual prediction of this model that sometimes processing under focusing-attention conditions can be slower than that under divided-attention conditions.

Attention↗
PubMed1995

Preferred viewing distances for handheld and structurally fixed displays.

This research was conducted to define viewing distance characteristics of individuals engaged in ordinary reading tasks. Specific attention was directed to assessing the potential relationship between observed distance and individual resting point accommodation. Consistent, statistically significant differences were observed across variable handheld and structurally-fixed hardcopy display configuration conditions. Relationships between observed viewing distance and resting point accommodation were not apparent. These findings suggest that simple eye-to-display viewing distance is fundamentally different for handheld text presentations and for the same text presented in a configuration similar to that of a video display terminal.

Accommodation, Ocular↗
PubMedDate not supplied

Memory for a geometrical configuration in the cognitively impaired elderly.

The objective of this study was to analyze the mnemonic reconstruction of a complex spatial configuration in a group of 10 men and women, 70-88 years, with a diagnosis of organic brain syndrome and 10 controls matched for age, sex and educational background. A Piagetian model of a geometrical configuration with contingent and non-contingent properties was used to establish a heirarchical order of memorial organization for spatial structures. Subjects were evaluated one hour and one week after learning in reconstruction tasks. Although individuals with dementia performed more poorly than the age-matched controls, the hierarchy of chosen characteristics reflected a schematic progression in the organization of spatial memory in both groups.

Aged↗