Constancy of absolute judgments of size by normals and schizophrenics.

A study of size constancy in absolute judgments of chronic schizophrenics and normals under conditions of minimal distance cues showed a significant and consistent underestimation by schizophrenic Ss. The apparently inconsistent results from other studies of size and temporal constancy in schizophrenics were discussed and a hypothesis advanced which related the various findings as a function of loss of reality contact. Schizophrenics in good contact show stable overconstancy. Acutely disturbed schizophrenics show a loss of perceptual stability. Chronic schizophrenics have re-established perceptual stability through autistic frames of reference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparing effects of the horizontal-vertical illusion on grip scaling and judgment: Relative versus absolute, not perception versus action.

The discovery that the prehension component of an open-loop, two-fingered reach is largely immune to certain salient pictorial illusions has been used to suggest that humans possess 2 distinct visual systems, 1 that subserves perceptual judgment and 1 that mediates visually controlled action. In this article, the authors present evidence that suggests that the critical distinction is not that of reaching and judgment but of relative and absolute perception. Experiment 1 extends the findings of S. Aglioti, J. F. X. DeSouza, and M. A. Goodale (1995) and suggests that the manual prehension component of open-loop reaching is affected by the horizontal-vertical illusion to a much smaller degree than perceptual size judgments. In Experiments 2 and 3, however, when perceptual size judgment is directed at a single element of the display, this difference vanishes. Experiment 4 demonstrates that grip scaling is strongly affected by the illusion when a single reach is scaled to both the horizontal and vertical components of a triangular figure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus size scaling and foveal load as determinants of peripheral target detection

This paper reports two experiments on the effect of scaling the size of stimuli (using factors derived from consideration of cortical magnification) on the detection of peripheral visual targets. In the first experiment two levels of magnification, fully M-scaled and half M-scaled, were used to scale stimuli that were presented briefly. The performance decrement normally associated with increasing retinal eccentricity did not occur with both levels of magnification. There was an unexpected decline in performance at low eccentricities and possible explanations are discussed. The second experiment investigated the effects of half M-scaling on a peripheral detection task with the addition of foveal cognitive loading as would be found in many practical tasks. Half M-scaling improved performance with and without the presence of foveal loading, and the improvement was greater for the foveal load condition when the target was at the larger eccentricities. These results provide a useful indication of the possibility of reducing the effect of tunnel vision for visual inspection tasks on visual displays or, possibly, control panels through the development of variable resolution projection displays matching the psychophysical properties of the human visual system.     

Object search in nonscene displays.

When we look at a chair or a giraffe we cannot suppress a semantic interpretation of that image, although we need not name it (e.g., Smith & McGee, 1980). Given that classification of object images is mandatory, is it capacity free? Subjects attempted to detect the presence or absence of a target object, specified by basic-level name, in a 100-ms display of a nonscene (clock face) arrangement of one to six pictures of common objects. There was a sharp monotonic decrease in detectability as a function of the number of objects in the display, indicating that object detection under these conditions is an attention-demanding process. No benefit was observed for targets that were likely to co-occur with the distractors. This latter result is evidence against an account of the perceptual interference found for improbable objects in real-world scenes, which holds that the interference derives from an inventory listing of the objects without regard to their spatial relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual effects in scaling.

The effect of specific contextual levels upon empirical meaning of adjectives in scales was determined by 4 identical content forms. All 145 females got forms A and B, "which were in the context of 'food,' one week apart." After 2 weeks ? got a "roast beef" context and ? got the "stewed kidneys" context. The hypothesis that scale values of adjectives rated in a "food" context would increase when rated in a specific context of a highly acceptable food was verified. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Loudness scaling and masking in rats.

Two groups of Sprague-Dawley-derived rats (N?=?16) were trained on operant discriminations in which the discriminanda were 2 sound pressure levels of a 4-kHz tone. The discriminanda were chosen so that the loudness difference between stimuli was equivalent for each group when calculated from a power function with an exponent of .35. Half of each group learned the discrimination in quiet, and the other half learned it in a background of white noise. Within the quiet and the noise conditions, the asymptotic discriminability of stimuli separated by equal loudness differences was equivalent, and discriminability was lower in noise. This is consistent with both the human literature on masked loudness and a model of psychophysical scaling (R. Pierrel-Sorrentino and T. G. Raslear; see record 1981-20539-001) in which animals judge perceived differences between stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Loudness scaling in rats and chinchillas.

In 2 experiments, 10 male chinchillas and 24 male Sprague-Dawley-derived rats were trained on operant discriminations in which the discriminative stimuli were 2 different sound pressure levels of a 4-kHz tone. Two or more of these 2-intensity discriminations were used at each of 3 levels of discriminability: high, medium, and low. For any given level, each of the stimulus pairs used differed in decibel separation but were similar in loudness-unit differences calculated from a power function. Different groups of Ss trained on stimuli separated by equal numbers of loudness units produced equivalent performances at each of the 3 levels of discriminability. It is concluded that loudness growth for both of these species, as for humans, is well described by a power function (S. S. Stevens's 1961 law). For the chinchilla the exponent is .25, and for the rat it is .35. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial localization in sequential letter displays.

Conducted 2 experiments with a total of 26 undergraduates to investigate the ability to locate letters presented successively along a horizontal row. The letters were displayed for 5 msec, and the inter-letter interval varied between 0 and 200 msec. In Exp I, localization decreased as the inter-letter interval was increased to 50 msec. With further increments in inter-letter interval, performance improved. However, there was a correlation between the positions of the letters in space and in time. Exp II indicated that the recovery in spatial localization with inter-letter intervals greater than 50 msec is spurious (i.e., it does not occur if the correlation is minimized). (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conceptual masking in brief visual displays.

Examined a paradigm used to study conceptual masking. This paradigm uses a variant of the partial report procedure, wherein a display of characters is preceded or followed by a probe character and Ss must report whether the probe was in the display or not. Ss were 7 undergraduates. Results show that neither specific orienting effects of the probe nor eye movements to the probe character could explain the pattern of data found in earlier studies (V. Di Lollo and M. Moscovitch; see record 1984-14011-001). Data are discussed in the context of P. Dixon's (see record 1986-21077-001) model of performance within this paradigm. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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 kinetic depth effect ratings are not treated interchangeably. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Color coding and visual separability in information displays.

12 experimental Ss performed both visual search and class counting tasks, viewing displays containing 20, 60, or 100 items. Each item consisted of a vector, letter, and 3-digit number grouped together, and was presented as white-on-black in some displays, or in 1 of 5 colors. The color code was redundant with the 5 class-designator letters that were used. Average search and counting time, and counting errors, increased with increasing display density (number of items). None of these measures varied significantly among the 5 different target classes (colors). Addition of the redundant color code resulted in an average time reduction of 65% in the visual search task and 69% in the counting task, with a reduction of 76% in errors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human information processing in navigational displays.

Studies of abstract picture–sentence verification tasks have shown that people exhibit directional biases in the way they think about spatial orientation; for example, they decide faster about diagrams involving the term "right" than the term "left." The roles of these and other human limitations in processing displays of target and own-ship movements were evaluated with 2 groups (experienced and inexperienced) of 7 submarine officers each. In 2 1-hr sessions, each officer made 192 judgments of computer-generated diagrams repesenting the linear movements of own ship and target ship. The standard picture verification task paradigm was used to measure response times. Direction of motion, right or left, per se did not reliably influence response time, but the S's level of experience, amount of practice at the task, display truth value, stimulus congruity, and stimulus–response compatibility did. The study demonstrates how the effects of factors isolated through basic research can be demonstrated in operationally relevant tasks. Implications for training are discussed. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anchoring of lightness values in center-surround displays.

Luminance ratios, by themselves, do not specify lightness values without an anchoring rule. The anchoring rule most often assumed for simple displays is that white is assigned to the highest luminance. It is proposed here that, for simple center–surround stimuli, the rule is based on geometry rather than photometry: White is assigned to the background, regardless of relative luminance values. Both a disk–annulus configuration and a disk–ganzfeld configuration were used to test the perceived lightness of centers and surrounds. In the disk–annulus case, assignment of white was based on a compromise between these 2 rules. For the disk–ganzfeld case, assignment of white seemed to be based entirely on the surround-as-white rule, and disks brighter than the ganzfeld background appeared luminous. It is argued that the disk–ganzfeld configuration, not the disk–annulus configuration, represents the minimal conditions for the appearance of surface lightness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Accuracy of target detection in new-object and old-object displays.

In 4 experiments, the authors investigated accuracy of detecting a target among nontargets. In some experiments, the target was a second-order square of stationary lines on a background of downward-moving lines, and nontargets were second-order squares of upward-moving lines. In other experiments, target and nontarget squares and background were shades of gray. The principal comparison was between "new" and "old" object displays. In new-object displays, search items appeared abruptly and one might be a target. In old-object displays, search items appeared abruptly, and after a delay one might become a target. Search displays in both conditions terminated shortly after target onset. Except when target onset was associated with the sole luminance change in a display, targets were much better detected in new-than in old-object displays. It is suggested that object onsets elicit a brief stimulus-driven enhancement of attention to the new objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)