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.     

Science and politics: Dangerous liaisons

In contrast to the opinion of numerous authors (e.g. R. Rudner, P. Kitcher, L. R. Graham, M. Dummett, N. Chomsky, R. Lewontin, etc.) it is argued here that the formation of opinion in science should be greatly insulated from political considerations. Special attention is devoted to the view that methodological standards for evaluation of scientific theories ought to vary according to the envisaged political uses of these theories.I wish to thank the Alexander von Humboldt Foundation for having supported the work on this paper.     

Conceptualizations of valence and instrumentality: A fourfold model

Within the framework of valence-instrumentality (VI) theory, a fourfold model is developed to predict the contribution which is made by one outcome of an alternative to the valence of that alternative. The proposed model uses four subjective conditional probabilities which are based on the presence and absence of an alternative, and on the occurrence and nonoccurrence of an outcome. Valence is defined as the difference between the attractiveness values of the occurrence of an alternative (or an outcome) and the nonoccurrence of an alternative (or an outcome). Also, differences between subjective probabilities replace instrumentalities. Alternative valence-instrumentality formulations are analyzed in relation to the proposed fourfold model. The proposed model can be understood as a consistent application of Vroom's model (1964, Work and motivation, New York: Wiley), while other models are judged to be relatively deficient. The fourfold model, in combination with a matrix formulation of expectancy concepts, addresses a number of criticisms of VI theory and makes possible a test of the theory within the limits of its own assumptions.     

The Craik-O’Brien-Cornsweet effect: New varieties and their theoretical implications

New visual displays related to the Craik-O’Brien-Cornsweet effect are presented and their relevance for theories of the effect is assessed. The displays include a luminance cusp that does not induce the standard effect, an illusory chessboard, a brightness variant of the impossible staircase, and a display in which brightness varies with stimulus motion. Theories of the effect are grouped within the nonisomorphistic, the cognitive, and the mechanistic approaches. The nonisomorphistic approach is criticized as being seriously incomplete. Existing cognitively oriented proposals are criticized as inadequate. Mechanistic theories are divided into integration theories, which model the visual processing stages with standard mathematical operations such as differentiation and integration, and filling-in theories, which stress the processing dynamics of interconnected neural networks. The reported variations of the Craik-O’Brien-Cornsweet effect support the latter class of theories.