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.     

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.     

Defaults in update semantics

The aim of this paper is twofold: (i) to introduce the framework of update semantics and to explain what kind of semantic phenomena may successfully be analysed in it: (ii) to give a detailed analysis of one such phenomenon: default reasoning.     

TEACHING MULTIPLICATION FACTS TO STUDENTS WITH LEARNING DISABILITIES

Multiple baseline designs were used to examine the effects of an instructional package on accuracy of performance in solving multiplication facts by 3 students with learning disabilities. The instructional package included the following components: (a) a modified instructional sequence in which multiplication facts were grouped into the zeros, ones, doubles, fives, and nines categories, and those remaining; (b) identification of the category in which each fact belonged; (c) mnemonic strategies associated with solving facts in each category; and (d) steps to be completed for solving facts in each category. Results indicated that the instructional package produced substantial and immediate effects. After receiving instruction, a participant's accuracy was often 100%, and this was maintained throughout the evaluation even as other strategies were introduced. Comparable results occurred across students, demonstrating replication of the effects of the instructional package.     

Compassion: An east‐west comparison

Compassion is an emotion that occupies a central position in Mahāyāna Buddhist philosophy while it is often a neglected subject in contemporary western philosophy. This essay is a comparison between an Eastern view of compassion based upon Mahāyāna Buddhist perspectives and a western view of the same emotion. Certain principles found in Mahāyāna Buddhist philosophy such as the Bodhisattva Ideal, and suffering (dukkha) to name two, are explored for the information they contain about compassion. An essay by Lawrence Blum is taken as representative of a Western view (but not exclusively) and it is analyzed for its shortcomings in light of the Buddhist view. The conclusion briefly describes the value of understanding an eastern view on compassion as a means of filling the void one finds in western medical ethics discourse which focuses so heavily, and redundantly, upon issues such as patient autonomy and paternalism.     

Controversies over integrity testing: Two viewpoints

In the August 1993 issue ofJournal of Applied Psychology, Deniz Ones, Vish Viswesvaran, and Frank Schmidt published a monograph on the validity of integrity tests as revealed by meta-analysis. They concluded that integrity tests have substantial and generalizable predictive validity for criteria of both overall job performance and counterproductive behaviors on the job (e.g., disciplinary problems, absenteeism, rule breaking, violence on the job, theft, etc.). During the Fall of 1992, the authors sent a preprint of this study to David Lykken of the University of Minnesota, stimulating the exchange of letters that is reproduced here. The doubts, concerns, and feelings about integrity tests expressed by Professor Lykken are likely to be shared by others. The responses by Professors Schmidt, Ones, and Viswesvaran attempt to show that these worries are unfounded.     

Visual aftereffect of texture density contingent on color of frame

An aftereffect of perceived texture density contingent on the color of a surrounding region is reported. In a series of experiments, participants were adapted, with fixation, to stimuli in which the relative density of two achromatic texture regions was perfectly correlated with the color presented in a surrounding region. Following adaptation, the perceived relative density of the two regions was contingent on the color of the surrounding region or of the texture elements themselves. For example, if high density on the left was correlated with a blue surround during adaptation (and high density on the right with a yellow surround), then in order for the left and right textures to appear equal in the assessment phase, denser texture was required on the left in the presence of a blue surround (and denser texture on the right in the context of a yellow surround). Contingent aftereffects were found (1) with black-and-white scatter-dot textures, (2) with luminance-balanced textures, and (3) when the texture elements, rather than the surrounds, were colored during assessment. Effect size was decreased when the elements themselves were colored, but also when spatial subportions of the surround were used for the presentation of color. The effect may be mediated by retinal color spreading (Pöppel, 1986) and appears consistent with a local associative account of contingent aftereffects, such as Barlow’s (1990) model of modifiable inhibition.     

The relationship between frontalis muscle activity and self-reports of headache pain

The relationship between levels of frontalis muscle activity and self-reports of pain was evaluated in two studies. In Study I frontalis muscle activity and self-reports of pain collected during biofeedback treatment of muscular contraction headache clients were correlated. In Study II frontalis EMG activity was increased and decreased using biofeedback techniques while concurrent reports of headache pain were recorded. The results of Study I indicated a significant relationship between EMG activity and reported headache pain for only two of the five subjects studied. The biofeedback procedures in Study II were associated with reliable increases and decreases in EMG activity. Concordance between EMG and pain reports occurred only during the EMG increase condition. Overall correlations were significant for one of the 2 subjects. The results suggest that EMG activity may not be sufficient to account for pain reports in all chronic headache clients, and variables other than EMG activity may be influencing reports of pain in some patients.