Signification et signifiance

Sans résumé     

Preventing Substance Abuse Among American-Indian Adolescents: A Bicultural Competence Skills Approach

Tobacco, alcohol, and drug use are problems for American-Indian people. We reviewed these problems and the explanations for them and described a bicultural competence skills approach for preventing substance abuse with American-Indian adolescents. Data from a study of that approach suggest its efficacy with American-Indian youth. At posttest and a 6-month follow-up, American-Indian subjects who received preventive intervention based on bicultural competence skills concepts improved more than did American-Indian subjects in a no-intervention control condition on measures of substance-use knowledge, attitudes, and interactive skills, and on self-reported rates of tobacco, alcohol, and drug use. Our findings have implications for future substance-abuse prevention research with American-Indian people.     

The height of a stereokinetic cone: A quantitative determination of a 3-D effect from 2-D moving patterns without a “rigidity assumption”

Summary When a circular disc with an eccentric dot painted on it is set in slow circular motion, a three-dimensional solid object appears to the observer: the stereokinetic cone. The cone shows a well-defined height and tilt. All current theories of how the visual system can extract 3-D percepts from 2-D moving patterns, are based on a rigidity assumption hypothesis. But this assumption cannot explain why the stereokinetic cone appears to have a well-defined height. An alternative hypothesis is proposed here, which avoids the rigidity assumption and is based on a minimization process of the relative velocity differences between all the points of the rotating pattern. The hypothesis allows a quantitative prediction of the stereokinetic cone height both when the rotating disc is circular and when it is elliptical. The predictions are in good agreement with previously reported experimental results and with our own observations.     

Critique,rhétoricité, communicabilité

La critique et la théorie littéraires contemporaines présentent un paradoxe: elles notent, par la référence à la rhétorique, la rupture de la propriété argumentative ou persuasive de l'oeuvre; elles préservent cependant l'hypothèse d'une propriété conversationnelle du littéraire — hypothèse qui n'est pas véritablement explicitée. Ce paradoxe, essentiellement lisible dans la déconstruction, l'est aussi dans les propositions de Sartre, dans la pensée du dehors de Foucault, dans le dialogisme de Bakhtine. Le paradoxe revient, de fait — telle est la thèse de cet article — à énoncer une propriété rhétorique et persuasive de l'oeuvre, au moyen d'une référence à la rhétorique d'abord confondue avec la tropologie et avec l'effacement du jeu persuasif. Cette ultime propriété rhétorique et persuasive est identifiable par l'alliance de lasuspension, qui caractérise le texte littéraire dès lors qu'il est placé sous le signe de la rupture de l'argument et de la persuasion, et du jeu anaphorique, lui-même indissociable du questionnement que suscite la suspension. A partir du constat de ce questionnement, il convient de dire que le texte littéraire est ce qui fait fond à la disparité du doxique, et que celui-ci apparaît comme le répondant provisiore et variable de lacasuistique que constitue le texte littéraire.     

Visual perception of surface curvature: psychophysics of curvature detection induced by motion parallax

The continuous approach to optic-flow processing shows that the curvature of a moving surface is related to a second spatial derivative of the velocity field, the spin variation (Droulez & Cornilleau-Pérès, 1989). With this approach as a theoretical framework, visual sensitivity to the curvature of a cylinder in motion was measured using a task of discrimination between cylindrical and planar patches. The results confirm the predictions suggested by the theory: (1) Sensitivity to curvature was always greater when the cylinder axis and the frontal translation were parallel than when they were orthogonal. The ratio of curvature detection thresholds in the two cases was between 1.3 and 2.5; the value predicted from the spin variation theory is about 2. (2) Sensitivity to curvature increased strongly with the velocity of the motion but was only weakly affected by its amplitude and the duration of viewing for the range of values used in our experiments.