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PubMed2005

Configural processing and perceptions of head tilt.

Configural processing is important for face recognition, but its role in other types of face processing is unclear. In the present study, participants made judgments of head tilt for faces in which the vertical position of the internal facial region was varied. We found a highly reliable relationship between inner-face position and perceived head tilt. We also found that changes in inner-face position affected the perceived dimensions of an individual unchanged facial feature: compared to control faces, nearly two-thirds of faces in which the features had been moved down were judged to have a longer nose. This finding suggests an early integration of configural and featural processing to create a stable holistic percept of the face. The demonstration of holistic processing at a basic perceptual level (as opposed to during face recognition) is important as it constrains possible models of the relationships between featural and configural processing.

Adolescent↗
PubMed2006

Peripheral neuropathy and object length perception by effortful (dynamic) touch: a case study.

The spatial extents of hand-held objects can be perceived nonvisually by wielding them. This ability of effortful or dynamic touch to exploit the mass moments of an object to perceive its length was evaluated with a 40-years old right-handed woman with surgically treated Arnold-Chiari Type 1 Malformation and cervical syrinx. At the time of the experiment she presented with loss of discriminative touch in the left arm but no comparable sensory deficits in the right arm or the lower extremities. She could neither identify objects in her left hand nor tell that they were in the hand while manipulating them. She could, however, grasp an object tightly and wield it on request. In the experiment she wielded weighted rods of 45, 60, and 80cm length about the wrist. There were two main results. First, her nonvisual perception of rod length by the insensate left arm scaled systematically with rod moment of inertia. The scaling matched that of the intact right arm and the nondominant arm of haptically unimpaired controls tested with rods of similar dimensions. Second, her right arm was superior in accuracy and reliability than her insensate left arm and was equal to or better than the dominant arm of the control group on key measures of nonvisual length perception. The first result was evaluated in respect to the notions of numb touch and differences in the neural bases of discriminative and effortful touch. The second result was discussed in terms of contralateral cortical enhancement by deafferentation.

Adult↗
PubMed1982

Visual perceptual deficits in clumsy children.

In a previous study clumsy children were found to be impaired in their ability to match the length of successively presented straight lines, and the ability to perform this task correlated with their degree of motor impairment [3]. The present experiments explore two possible explanations for this pattern of results. One possibility is that this earlier result tapped a memory deficit in the clumsy children. The first experiment shows that the clumsy children still experience difficulties in matching the length of a line to a second line which is simultaneously present. This suggests the difficulty is one of perception and not memory. The second experiment explores whether faulty perception of length in the clumsy children is related to eye movement problems. No support for this idea was found; with tachistoscopic presentations at durations which exclude subjects making eye movements the clumsy children are still clearly impaired in judging the length of lines.

Child↗
PubMed2004

The effect of cane length on the haptic perception of height.

PURPOSE: The purpose of this investigation was to determine whether the ability to haptically perceive object height is a function of the length of cane being wielded by blindfolded individuals. METHOD: Fifteen sighted females between the ages of 18 and 25 years volunteered to participate in the study. Five different heights of wooden blocks were haptically explored with four different cane lengths (0.92, 1.22, 1.37 and 1.67 m), cane length order being randomized across 2 days of testing. Subjects were asked to report whether the explored block's height was taller, shorter, or equal to that of a previously presented standard block. The percentages of correct judgments for each cane and block height combination were subjected to statistical analysis. RESULTS: The analysis revealed significant main effects for cane length, F (3, 42) = 9.47, p < 0.0001, and block height, F (4, 56) = 17.69, p < 0.0001. The interaction of cane length and block height was not significant, F < 1. The accuracy of haptic perception improved with decreased cane length and increased difference in height from the standard block. CONCLUSIONS: Contrary to previous research on haptic perception in which probe length was found not to affect judgment accuracy, the present study found a marked influence of cane length on perceptual accuracy. This finding indicates that length is an important property that should be taken into account when prescribing canes for the visually impaired.

Adolescent↗
PubMed1980

Separable and integral responding by children and adults to the dimensions of length and density.

The classifying behavior of 5-year-old children and adults was examined in 2 studies of restricted classification using triads of stimuli composed of the dimensions of length and density. Subjects could classify on the basis of dimensional structure, overall similarity, or neither. Adults showed a majority of dimensionally based responses, while children gave a majority of similarity-based responses in experiment 1. This pattern is consistent with the notion of separable perception for adults and integral perception for children. The results of a pretask for experiment 2 in which subjects were required to make dimensional comparisons indicate that children's integral responding is not based on an inability to access dimensional relations. The results are discussed in terms of possible strategic differences underlying separable and integral responding.

Adult↗
PubMed2002

Scale invariance is driven by stimulus density.

Scale invariance refers to aspects of visual perception that remain constant with changes in viewing distance. Previously, Dakin and Herbert [Proc. Roy. Soc. B. 265 (1397) (1998) 659] reported that the spatial integration region (IR) for mirror symmetry in bandpass noise is scale invariant because its dimensions scale with the inverse of peak spatial frequency. In bandpass noise, however, peak spatial frequency covaries with stimulus numerosity (i.e. the total number of information samples) and density (i.e. the total number of information samples per unit area). In this study, we report four experiments that decoupled properties of the retinal image affected by viewing distance--spatial frequency, numerosity, size, and density--and measured their effect on IR size. Stimuli consisted of bandpass microelements with vertically mirror-symmetric but otherwise random positions, and we measured observer resistance to random jitter imposed on microelement position. Results show that jitter resistance and IR size vary with the inverse of stimulus density but are unaffected by changes in stimulus spatial frequency, numerosity, or size. We found the IR has a 2:1 height-to-width aspect ratio and integrates information from approximately 18 microelements regardless of their spatial separation. Our results reveal that stimulus density plays a central role in the visual system's implementation of scale invariance. Using an ideal-observer, we demonstrate that scale invariance reflects genuine neural scale selection rather than a physical limitation on the stimulus' information content. Our findings that jitter resistance and IR size vary with the inverse of density challenge current models of spatial vision but can be reconciled with a model that compares the output of bandpass non-Fourier mechanisms to select spatial scales that match stimulus density.

Humans↗
PubMed1994

Müller-Lyer illusion and perception of numerosity.

Illusion of numerosity can be observed in many of the classical illusions of linear extent by replacing the uninterrupted lines with rows of dots. Using the method of constant stimuli both length and numerosity illusions move in the same direction, whereas using a magnitude-estimation method the two illusions move in opposite directions. Two experiments show that this inversion occurs also in the Müller-Lyer illusion.

Attention↗
PubMed2003

Body size estimation: testing a new mirror-based assessment method.

OBJECTIVE: The aim of the current study was to compare a new ecologically valid method of body size estimation with an existing, commonly used method. METHOD: The new method uses a "mirror-sized" image and measures perception rather than memory of body size. Fifty-five healthy women participated in the study. RESULTS: Body size estimations with the new method were significantly larger than with the existing method (p <.001). This difference was specific to body size and was not seen for estimation of neutral images. DISCUSSION: The results of the study show that different body size estimations are made with the new more ecologically valid method compared with the existing method. This finding has important implications for research into the factors influencing the perception of body size.

Adult↗
PubMed1977

Perceived exertion and stimulus intensity modulation.

Perceptual augmentation and reduction were considered contrasting styles of Stimulus Intensity Modulation. Differences in perceived exertion between augmenters and reducers were determined for three cycle ergometer work loads. Subjects were 20 males having similar physiological characteristics. Stimulus Intensity Modulation was determined by kinesthetic figural aftereffect. Augmenters rated their perceptions of physical exertion to be more intense than reducers at 450, 750 and 1050 kpm/min. Differences in physiological responses between augmenters and reducers were not significant at the three work loads. Style of Stimulus Intensity Modulation appeared differentially to influence perceived exertion at the work levels studied.

Blood Chemical Analysis↗
PubMed1982

The moon illusion: II. A reference theory.

The present theory provides explanations for the moon illusion and related issues involving size and distance perception in natural, outdoor settings. Although some assumptions of previous theories are rejected, other pivotal aspects are retained in this formulation. In particular, the present theory states that both the sky and ground are important referents in judging the spatial extent of the moon. Neither factor alone can account for all the available data, but quantitative models incorporating both factors do quite well when applied to the parametric findings of Holway and Boring, as well as to the results obtained by Kaufman and Rock. The reference theory and its associated class of specific models suggest new theoretical directions and experimental tests to narrow yet further the selection of appropriate explanations for one of visual perception's oldest unsolved puzzles.

Astronomical Phenomena↗
PubMed1998

Threshold effect in visual perception of geometrical figures.

Filtering of the input image has been shown to play a central role in several aspects of visual perception. In our experiments in visual perception of the area of geometrical figures the orientation in random dot patterns, and some visual illusions, we have shown that a threshold effect inferred from the filtering of the input image produces a perceptual error. This error has been explained by using the concept of Image Function. The present paper is a brief review of our experimental results and of the models we have proposed.

Humans↗
PubMed1978

Spatial perception in normal and psychotic people.

17 normal and 17 psychotic subjects, including schizophrenic, depressive, and delusional patients, were given a modified Arc-Circle Matching Test of spatial perception. There was no significant difference between the performance of the psychotic group and that of the control group in left-hand, right-hand, and total scores in this tactile test of spatial ability. Differences between males and females and between dextrals and non-dextrals were nonsignificant. Nevertheless, for all subjects, the left-hand scores were significantly superior to right-hand scores.

Dominance, Cerebral↗
PubMed2004

Patient's perception of location, form and size in case of cavity preparation.

The aim of the present study was to clarify the difference between the imagination of patients and the reality in regard to the location, the form and the size of the cavity in case of cavity preparation for dental restoration. Firstly, we manufactured the dummy dentition for simulated cavity preparation and the operator intra-orally prepared a cavity on the dummy dentition in subject to confirm its validity. Then, 5 operators intra-orally prepared prescribed cavities at the both sides of maxillary first molars on the dummy dentition in every one of 5 subjects with masking. We compared the location, the form and the area of these prepared cavities with those imagined by subjects, respectively. In 58% of cases, the subjects could accurately recognize the location of prepared teeth. And 34% of cases also determined the Class of cavity form. The imagined area was larger than the actual area and the difference was statistically significant (p < 0.001). These results suggested that the perception of the patients regarding the location and the form of the prepared cavity was inaccurate during cavity preparation and patients tended to overestimate amounts of removed tooth substance.

Adult↗
PubMed2005

Forming subjective representations of subjective representations: evidence of a subjective status bias.

In 3 studies and 2 pilot experiments, the author examined whether attending to the subjective status of mental representations would affect the ways humans view representational contents. The author found that simple drawing tasks were executed differently depending on whether or not the subject of the drawing was defined as a mental content (belief, imagination, perception). The results challenged particular lay epistemological concepts. They were partly accounted for by Gricean conversational rules (H. P. Grice, 1975), but the author postulated a subjective status bias to fully explain them. The discussion and recommendations for research center on the nature of this bias and relate it either to a tendency to conceive subjective representations as vague shadows of reality, or to an increased impact of the law of pregnance.

Adolescent↗
PubMed1990

Pigeon pattern perception: limits on perspective invariance.

Two experiments are reported in which the response of pigeons to perspective transformations of a pattern target was measured. In the first experiment an alphabet letter was taken as the pattern target (the 'positive') and the response to its perspective transforms was compared to the response to nontarget letters ('negatives') over the course of discrimination training. In the second experiment irregular quadrilaterals were used as positives and the responses to slight perspective deformations of the prototypes were compared to the responses to random transformations of the same magnitude under steady-state conditions. The amount of differential responding depended on the type of transformation. There was no differential response to targets rotated in the picture plane or around the horizontal axis in either experiment. There was differential response to small reductions and enlargements of the target. There was also differential response to translated targets, and this was seen irrespective of the amount of displacement. Results from targets rotated around the vertical axis were erratic, some target-plus-angle combinations elicited differential responding, but most did not. The erratic responses are attributed to symmetries in pattern elements that were abstracted as critical features. Pigeons therefore exhibit no true rotation invariance, limited size invariance, and complete shift invariance. It is argued that size invariance, but not position invariance, may depend on prior exposure to the alternatives.

Animals↗
PubMedDate not supplied

[Visual nonverbal set in preschool- and schoolchildren].

Visual set for perception of unequal circles was formed in 5-6-year-old preschool- (n = 30) and schoolchildren (n = 43). Children of 5.3-6.1 years old formed a less rigid set than 9-10-year-olds. The reaction time to a probe stimulus significantly depended on the set stability and stage. The role of structural maturation of the frontal cortical areas in set formation and stability is discussed. The factor of set rigidity was shown to be significant for cognitive activity.

Age Factors↗
PubMed2005

Gender differences in body image and health perceptions among graduating seniors from a historically black college.

This study's purpose was to identify gender differences in body size awareness and perceived impact of weight on social interactions and risk for disease among young African-American adults. A cross-sectional survey of 318 African-American graduating seniors from a historically black college or university (HBCU) was conducted. Data were collected on anthropometrics, body image, ideal weight, perceived risk for disease due to weight, and impact of weight on social interactions. Only 39% of males who were overweight perceived themselves as overweight compared with 68% of overweight females. Eighty percent of females and 63% of males expressed some body size dissatisfaction. Fewer obese males (38%) perceived a risk for disease due to their weight compared with obese females (64%), p<0.01. Males perceived greater impact than females of their weight on social interactions, with extremely obese males perceiving the greatest impact. Perceived risk for disease due to weight was related to body mass index, family weight history, body awareness and income, but not body size satisfaction. Findings suggest gender differences in the self-perception of body size, accuracy of body size perception, and understanding of acceptable weight ranges. Awareness of acceptable weight ranges and consequences of overweight needs to be raised.

Adult↗