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At least 145 records · Page 8Linked to original sources
PubMed2002

Perception of two-body center of mass.

Participants estimated the perceptual center of mass between two horizontally oriented black dots varying in size and distance. Experiment 1 showed that estimates, measured as distance from the larger dot's center, decreased with an increase in size ratio between the dots and a decrease in the distance between them, as predicted by the physical center-of-mass equation. The results were replicated and extended in further experiments with different ratios and distances. In all experiments, the true center was consistently overestimated, either because the stimuli were perceived in a low dimensionality or because of a hesitancy to place estimates near the larger dot's edge. In Experiment 4, the center was deliberately placed near this edge for one- and two-dimensional solutions. Participants still overestimated, indicating an "edge effect" as responsible.

Adolescent↗
PubMed1993

Realism of confidence in sensory discrimination: the underconfidence phenomenon.

This paper documents a very pervasive underconfidence bias in the area of sensory discrimination. In order to account for this phenomenon, a subjective distance theory of confidence in sensory discrimination is proposed. This theory, based on the law of comparative judgment and the assumption of confidence as an increasing function of the perceived distance between stimuli, predicts underconfidence--that is, that people should perform better than they express in their confidence assessments. Due to the fixed sensitivity of the sensory system, this underconfidence bias is practically impossible to avoid. The results of Experiment 1 confirmed the prediction of underconfidence with the help of present-day calibration methods and indicated a good quantitative fit of the theory. The results of Experiment 2 showed that prolonged experience of outcome feedback (160 trials) had no effect on underconfidence. It is concluded that the subjective distance theory provides a better explanation of the underconfidence phenomenon than do previous accounts in terms of subconscious processes.

Adult↗
PubMed1989

The effects of physical work, mental work, and quantity on children's time perception.

An experiment was conducted to examine the effects of work and quantity cues on children's time perception. Ninety-seven children in kindergarten and Grades 2, 4, and 6 lifted and transferred pipes under eight different conditions, after which they reproduced the perceived time taken to move the pipes. The conditions varied by quantity (two/four pipes), by mental work (no-matching/matching), and by physical work (light/heavy pipes). Significant main effects were found for quantity, physical work, and mental work, and for the quantity x age and mental work x physical work interactions. These results can help to disentangle possible confounds among these variables in the classic Piagetian experiments about their effects on time judgment and perception.

Attention↗
PubMed1989

Bias effects on magnitude and ratio estimation power function exponents.

A bias model of relative judgment was used to derive a ratio estimation (RE) power function, and its effectiveness in providing estimates of exponents free of the effects of standards was evaluated. The RE bias model was compared with the simple RE power function that ignores bias. Results showed that when bias was not taken into account, estimates of exponents exhibited the usual effects of standards observed in previous research. However, the introduction of bias parameters into the RE power function virtually eliminated these effects. Exponents calculated from "equal-range segments" (e.g., low stimulus range vs. high stimulus range) judged by magnitude estimation (ME) were examined: the effects of equal-range segments on exponents were much stronger for ME than standards were for RE, using the bias model.

Attention↗
PubMed1993

Center of mass perception and inertial frames of reference.

Center of mass perception was investigated by varying the shape, size, and orientation of planar objects. Shape was manipulated to investigate symmetries as information. The number of reflective symmetry axes, the amount of rotational symmetry, and the presence of radial symmetry were varied. Orientation affected systematic errors. Judgments tended to undershoot the center of mass. Random errors increased with size and decreased with symmetry. Size had no effect on random errors for maximally symmetric objects, although orientation did. The spatial distributions of judgments were elliptical. Distribution axes were found to align with the principle moments of inertia. Major axes tended to align with gravity in maximally symmetric objects. A functional and physical account was given in terms of the repercussions of error. Overall, judgments were very accurate.

Adolescent↗
PubMed1993

Center of mass perception: perturbation of symmetry.

Bingham and Muchisky (1993) found that observers were very accurate in determining the location of the center of mass in planar objects. Systematic errors were affected primarily by object orientation, while random errors varied with the amount of symmetry. Radial and axial reflective symmetry affected errors in different ways. In the current study, we investigated the different effects of axial reflective versus rotational symmetry. All random errors decreased with increasing rotational symmetry. Axial reflective symmetry further reduced errors in the direction perpendicular to the axis. We replicated the effect on systematic error of orientation. However, we also found an effect of the perturbation of symmetry that suggested that observers used an approximation to symmetry. To investigate this possibility, we constructed a series of objects in which axial reflective symmetry was established and then perturbed by varying amounts. We found that systematic errors were structured by the underlying approximate symmetries, and we discuss the problem of quantifying symmetry.

Adolescent↗
PubMed2001

[Health behaviors among first degree students at the Free University of Brussels].

For several years, quality of life is used as a measure of health status. As university constitues a specific setting for young adults, the Health Service of the french-speaking Free University of Brussels initiated a survey in order to study health behaviours of students from the first grade. During the academic year 1998-99, 3,185 students were surveyed in the first degree, using an anonymous self-completed questionnaire with the following topics: health perception, weight, social support, emotional well-being, tobacco, alcohol, medicines, cannabis and ecstasy use as well as access to general practitioner. Body Mass Index was computed and emotional well-being was approached using CES-D scale. Results are presented by gender and faculty. Mutivariate analysis was also realised using logistic regression. In general, results confirm the data resulting from other studies in general population as well as at school. Nevertheless, results show that health is a problem for a minority of students and is a "whole" that has to be approached globally. Moreover, data give a basis to define priorities and strategies to improve students' physical and mental well-being at university. Results are also useful to better target these actions to those at needs.

Adult↗
PubMed1989

Understanding collision dynamics.

In two experiments we investigated people's ability to judge the relative mass of two objects involved in a collision. It was found that judgments of relative mass were made on the basis of two heuristics. Roughly stated, these heuristics were (a) an object that ricochets backward upon impact is less massive than the object that it hit, and (b) faster moving objects are less massive. A heuristic model of judgment is proposed that postulates that different sources of information in any event may have different levels of salience for observers and that heuristic access is controlled by the rank ordering of salience. It was found that observers ranked dissimilarity in mass on the basis of the relative salience of angle and velocity information and not proportionally to the distal mass ratio. This heuristic model was contrasted with the notion that people can veridically extract dynamic properties of motion events when the kinematic data are sufficient for their specification.

Acceleration↗
PubMed1986

Alternative matrix seriation, traditional seriation, and multiple classification.

This study investigated the structural relationships between traditional seriation tasks derived from Piaget's publications and alternative matrix seriation on the one hand, and alternative matrix seriation and multiple classification on the other. Subjects were 464 children from two kindergartens and three primary schools, Grades 1 through 6 who completed these three types of tasks. Factor analysis revealed that the alternative matrix seriation tasks (often used in neo-Piagetian research) did not reflect the same underlying concept as the traditional seriation tasks derived from Piaget's publications. In contrast, we found that alternative matrix seriation referred to the same underlying concept as multiple classification. We concluded that the alternative matrix seriation tasks cannot serve as a replacement for the traditional seriation tasks in assessing a child's seriation capacity.

Child↗