ON ULTIMATE EPISTEMIC FOUNDATIONS1

This paper is a contribution to the debate on epistemic foundationalism. Section I expounds and criticises Hans Albert's critical rationalist antifoundationalism position. Section I1 discusses Karl-Otto Apel's ‘transcendental pragmatic’ argument for ultimate epistemic foundations. Section III suggests how the latter argument can be restated so as to avoid ambiguity and yield a plausible case for epistemic foundationalism.     

DOUBLE DISSOCIATION BETWEEN MEMORY SYSTEMS UNDERLYING EXPLICIT AND IMPLICIT MEMORY IN THE HUMAN BRAIN

Abstract— Amnesic patients have impaired explicit memory that is evident in poor recall and recognition of words, yet can have intact implicit memory for words as measured by repetition priming, the enhanced efficiency for reprocessing those word's. The dissociation between explicit and implicit memory for words is a fundamental characteristic of normal cognition that could reflect two different functional architectures of the human brain two separate processing systems or two levels of operation of a single system with implicit memory less demanding of that system. We present a patient who has a lesion in the right occipital lobe and who showed intact explicit and impaired implicit memory for words. The deficit was specific to visual priming. The double dissociation between explicit and implicit visual memory for words indicates that separate processing systems mediate these two forms of memory, and that a memory system in right occipital cortex mediates implicit visual memory for words.     

Extraction of relief from visual motion

We quantified the ability of human subjects to discriminate the relative distance of two points from a slanted plane when viewing the projected velocities of this scene (orthographic projection). The relative distance from a plane (called relief) is a 3-D property that is invariant under linear (affine) transformations. As such, relief canin principle be extracted from the instantaneous projected velocity field; a metric representation, which requires the extraction of visual acceleration, is not required. The stimulus consisted of a slanted planeP (specified by three points) and two pointsQ ₁ andQ ₂ that are non-coplanar withP. This configuration of points oscillated rigidly around the vertical axis. We have measured thesystematic error andaccuracy with which human subjects estimate the relative distance of pointsQ ₁ andQ ₂ from planeP as a function of the slant of_P. The systematic error varies with slant: it is low for small slant values, reaches a maximum for medium slant values, and drops again for high slant values. The accuracy covaries with the systematic error and is thus high for small and large slant values and low for medium slant values. These results are successfully modeled by a simple relief-from-motion computation based on local estimates of projected velocities. The data are well predicted by assuming (1) a measurement error in velocity estimation that varies proportionally to velocity (Weber’s law) and (2) an eccentricity-dependent underestimation of velocity.     

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.     

The dynamics of Prägnanz

Summary There is quite wide-spread agreement about the relevance of pattern Pragnanz (Koffka, 1935) with respect to the human interpretation of visual patterns. There is less agreement about whether pattern Pragnanz is based solely on pattern information (static) or also on the history of the perceiver (dynamic). In Van Leeuwen and Van den Hof (1991), experimental data concerning serial patterns are presented within the framework of the dynamic-network approach initiated by Buffart (1986, 1987). These experimental data are claimed to give evidence against the static-coding approach initiated by Leeuwenberg (1969, 1971). In the present paper, however, I show first that Buffart's theoretical basis is incorrect, and that in fact Leeuwenberg's static-coding approach is the basis for the dynamic-network approach. Second, I show that those experimental data rather give evidence in favor of the static-coding approach, by using those same data for a test of the most recent static-coding model (Van der Helm & Leeuwenberg, 1991; Van der Helm, Van Lier, & Leeuwenberg, 1992). Finally, I propose a reconciliation between the two approaches, in the sense that the dynamic-network model could be shaped in such a way that it yields a simulation, and maybe even an enrichment, of the static-coding model.     

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.