Bit-plane layering for high-resolution EGA and VGA graphics on the IBM PC/XT/AT

Each page of video memory comprises four parallel planes that can be manipulated and displayed independently or in combination. A technique is described that involves programming the video hardware to achieve this. The utility of well-known video programming technology, such as the tachistoscope display, is thereby extended. Assembly language code is included, and a demonstration program is described.     

Impact of a prevention program on aggressive children's friendships and social adjustment

A group of 46 aggressive boys aged 8 to 9 years participated in a prevention program aimed at reducing their externalizing problems in the short term and at preventing delinquency in the long term. Outcome measures were collected during the 3-year period following the prevention program. At that time, the boys were 10, 11, and 12 years old. Outcome measures included teacher ratings of aggressiveness and self-reports of delinquent behaviors. The boys' friends were rated on disruptive behaviors by their classmates. The experimental boys' outcome measures were compared to the measures obtained from 58 aggressive boys in a control group. The disruptive ratings of the experimental and control subjects' best friends were also compared. Differences in teacher-rated aggressiveness between the two groups increased from one year to the next for the 3-year followup period. Similarly, the friends' disruptive scores differed increasingly between the two groups over the 3-year period. The effect of the prevention program on the subjects' friendships and the mediating impact of friends with regard to social adjustment were stressed.This study was funded by the following agencies: National Welfare Grants Program of the Canadian Ministry of Health and Welfare, Conseil Québécois de la Recherche Sociale, Conseil de la Santé et des Services Sociaux Régional du Montréal Métropolitain, Fondation Cité des Prairies, Fonds FCAR-Centre et Equipes, Institut de la Recherche en Psycho-Education de Montréal, Centre d'Accueil le Mainbourg. Lucie Bertrand, Rita Béland, Michel Bouillon, Raymond Labelle, Hélène O'Reilly, and Daniel Reclus-Prince supervised or administered the intervention.     

Relativistic hidden variable theories?

I show that for any quantum dynamics and any choice of observables as hidden variables an adequate hidden variable theory always exists. I argue that hidden variable theories have no more problems in reconciling non-locality with relativity than no-hidden-variable theories.     

Shape discriminations of three-dimensional objects depend on the number and location of bends

In three experiments, subjects made shape discriminations of three-dimensional objects differing in orientation, number of bends, and location of bends (e.g., the central arm vs. a minor subarm). In general, encoding times at 0° disparity on bothsame anddifferent trials were affected by the number of bends, but only after a certain threshold of bends in the objects had been reached (Experiment 1). This effect was not due to the subjects’ having to search for matching ends of the objects (Experiment 2). In contrast, rotation rates were influenced by the location of the bends, but not by the number of bends per se (Experiment 3). The results support a representational scheme that is hierarchical, but not necessarily one in which the principal axis of an object is paramount.     

Perceived motion in structure from motion: Pointing responses to the axis of rotation

We investigated the ability to match finger orientation to the direction of the axis of rotation in structure-from-motion displays. Preliminary experiments verified that subjects could accurately use the index finger to report direction. The remainder of the experiments studied the perception of the axis of rotation from full rotations of a group of discrete points, the profiles of a rotating ellipsoid, and two views of a group of discrete points. Subjects’ responses were analyzed by decomposing the pointing responses into their slant and tilt components. Overall, the results indicated that subjects were sensitive to both slant and tilt. However, when the axis of rotation was near the viewing direction, subjects had difficulty reporting tilt with profiles and two views and showed a large bias in their slant judgments with two views and full rotations. These results are not entirely consistent with theoretical predictions. The results, particularly for two views, suggest that additional constraints are used by humans in the recovery of structure from motion.     

Text-contingent color aftereffects: A reexamination

Five experiments reexamined color aftereffects contingent on the semantic properties of text (Allan, Siegel, Collins, & MacQueen, 1989). The influence of different assessment techniques and the effect of eye movements and overlapping contour information on the induction of color aftereffects by word and nonword letter strings were determined. Experiment 1 showed that no aftereffect was found when a traditional method of assessing color aftereffects was used. Experiments 2 and 4 demonstrated color aftereffects forboth words and nonwords, but only when subjects fixated the same locus during induction and testing and only when assessed with the technique described by Allan et al. (1989). If, however, eye movements were made during induction, no color aftereffect was obtained (Experiment 3). Induction to nontext patterns with properties similar to those of text but with fewer overlapping contours resulted in a strong color aftereffect (Experiment 5). These results suggest that the color aftereffect contingent on text is very weak and is not dependent on semantic factors, but that it is a product of induction to local color and orientation information.     

An investigation of the sampling distributions of item discrimination indices

The sampling properties of four item discrimination indices (biserialr, Cook's indexB, theU–L 27 per cent index, and DeltaP) were investigated in order to ascertain their sampling properties when small samples drawn from actual test data rather than constructed data were employed. The empirical results indicated that the mean index values approximated the population values and that values of the standard deviations computed from large sample formulas were good approximations to the standard deviations of the observed distributions based on samples of size 120 or less. Goodness of fit tests comparing the observed distributions with the corresponding distribution of the product-moment correlation coefficient based upon a bivariate normal population indicated that this correlational model was inappropriate for the data. The lack of adequate mathematical models for the sampling distributions of item discrimination indices suggests that one should avoid indices whose only real reason for existence was the simplification of computational procedures.This research reported herein was performed pursuant to a contract (OE-2-10-071) with the United States Office of Education, Department of Health, Education and Welfare.