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Results for “SIZE PERCEPTION”

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PubMed1978

[Two kinds of apparent size distortion in the Ponzo illusion (author's transl)].

It was proposed that there are two kinds of apparent size distortion to be distinguished in the Ponzo illusion. The apparent size of the single line in the converging lines (CL) became larger as it was located nearer to the apex. However, this distortion could not predict the obtained illusion sufficiently. Hence there should be assumed another kind of size distortion in the perception of the size relation as a result of comparison of two paralle lines (PL). In this comparison process, breaking of the continuity of CL and elimination of the oblique components from CL had a slight decreasing effect on the illusion. Moreover, it was found in the various contour figures that the greater the separation of PL was, the larger the illusion was.

Adolescent↗
PubMed2006

Effects of motion parallax and perspective cues on perceived size and distance.

In three experiments we examined the relative effectiveness of motion parallax and two perspective cues for the perception of size and distance. The experimental stimuli consisted of two ellipses (a standard and a comparison) and a horizontal line that indicated the horizon. The subject's task was to report the apparent size and distance of the comparison stimulus relative to the standard stimulus. Two perspective cues were given by the relative heights of the two stimuli and the absolute height of the standard stimulus below the horizon. Motion parallax was defined by both the ratio and the difference in angular velocities between the two stimuli on the display. In experiment 1 we examined the effects of the two perspective cues and the motion parallax. In experiment 2 we eliminated the horizon line, and examined the role of the horizon in size and distance perception. In experiment 3 we separately evaluated the effects of motion parallax and the relative height cues. The results from the three experiments showed that the effect of motion parallax and the two perspective cues were different in three ways. First, the relative effectiveness of motion parallax and the two perspective cues differed for size and distance estimates. For size estimates, the motion parallax was more effective than the perspective cues (experiments 1 and 3). For distance estimates, the motion parallax was as effective as the two perspective cues (experiments 1 and 3). Second, the role of the horizon differed for size and distance estimates. The size estimates were strongly affected by the horizon, while the distance estimates were not affected much by the horizon (experiment 2). Third, the effective perspective cues differed for the size estimates and the distance estimates: size estimates were affected by the perspective cues as a combination of the horizon and relative height; distance estimates were affected by the perspective cues as an interaction between the absolute and relative heights without the horizon line.

Cues↗
PubMedDate not supplied

Perceptions of children's body sizes among mothers living on the Texas-Mexico border (La Frontera).

OBJECTIVES: The objectives of this study were to quantify mothers' perceptions of their children's sizes and explore mothers' views of child growth, diet, activity, and health. Photographs of children from the Berkeley Longitudinal Growth Study (on Centers for Disease Control and Prevention [CDC] Web site) were used to stimulate discussion with mothers about child sizes. DESIGN: A descriptive, cross-sectional study examined mothers' perceptions of their children's size and their beliefs about child size, growth, and health. SAMPLE: The convenience sample included 25 mother-child dyads of 3-year-old children at two Head Start Centers in a county on the Texas-Mexico border. All mothers self-identified as Hispanic. MEASUREMENT: Photographs of children were shown to elicit mothers' perceptions of children's body sizes. The children and mothers were weighed and measured and their body mass indices (BMIs) were computed. The mothers were interviewed about their beliefs on child health, growth, and feeding. RESULTS: No congruence was found between mothers' perceptions of child sizes in the pictures and their children's sizes. CONCLUSIONS: Using CDC photographs does not appear to be a useful way to educate mothers about child body sizes. A child who is happy, active, and can accomplish normal childhood activities is not considered by mothers as overweight, regardless of the child's BMI.

Adult↗
PubMed1995

Visual accommodation as a cue for size.

Accommodation micropsia is examined in the general context of ocular accommodation as a cue for object size. The nature and limits of accommodation micropsia and arguments dealing with the possible contribution of accommodation to the perception of size are reviewed. Literature on the anomalous myopias, the intermediate-resting hypothesis, and theories of ciliary muscle innervation is examined critically in so far as it bears on the accommodation-micropsia hypothesis. The anomalous myopias and evidence for the intermediate-resting hypothesis are well documented, but without a mechanism for proprioceptive feedback from the ciliary complex about the state of accommodation it can only be concluded that such feedback would have to be indirect, either via the reflex link with vergence, or possibly through the agency of efference-copy neurones.

Accommodation, Ocular↗