On optimal smoothing and derivative estimation from noisy displacement data in biomechanics

Estimating derivatives from noisy displacement data is a notoriously ill-posed problem in signal processing and biomechanics. Following the work of Wood and Jennings (1978) and Hatze (1979, 1981), the present paper describes the use of optimally regularized, natural quintic splines for estimating smoothed positions, velocities, and accelerations from equidistantly sampled, noisy position measurements. It appears that the nature of the boundary conditions of the data is of some importance, since various algorithms used hitherto result in artefacts throughout the data if the true derivatives at the record ends differ significantly from zero. Natural quintic splines do not suffer from this disadvantage below the third derivative.The ill-posed character of movement analysis has some interesting implications for movement synthesis and optimization, similar to the indeterminacy of muscular co-contraction from merely external, biomechanical measurements.     

Laterally induced impedance effects in vision

A linear integral equation for a system of mutually impeding points is developed and solved explicitly. Particular solutions are shown to be subharmonic functions for a large class of stimuli. Specialized forms of the general equation presented in this paper occur within a number of mathematical models of Mach bands. In addition to these known spatial properties, our results also show that the time course of this basic equation may be useful in developing models of transient neural activity as well as of temporal psychophysical phenomena, such as the Broca-Sulzer effect. Further, a spatial transfer function much like the low-frequency cutoff of empirically derived modulation transfer functions follows directly from our basic integral equation if the additional assumption of spatial homogeneity is imposed.     

Individualized behavior therapy for alcoholics: a third year independent double-blind follow-up.

An independently conducted double-blind study providing third year follow-up data for 53 of 70 male alcoholics who served as subjects in an experiment evaluating “Individualized Behavior Therapy (IBT)” techniques is reported. In the original study, subjects were initially assigned to either a controlled drinking or non-drinking (abstinence) treatment goal, and were then randomly assigned to either an experimental group receiving IBT or a control group receiving conventional state hospital treatment oriented towards abstinence. Previously reported results showed that IBT subjects functioned significantly better than control subjects throughout the first year of follow-up. Second year follow-up results found that IBT subjects treated with a controlled drinking goal functioned significantly better than their respective control subjects on a variety of measures, including drinking behavior. Differences between IBT subjects treated with a non-drinking goal and their control subjects did not retain statistical significance during the second year of follow-up. The independently determined follow-up data showed that during the third post-treatment year, subjects in the experimental groups generally functioned better than their respective control subjects. Comparison of the controlled drinking experimental group with its control group showed the significantly better functioning of subjects in the experimental condition on a number of drinking and other life functioning measures. Comparison of the non-drinking groups indicated only one possible difference on the drinking related measures involving a trend for subjects in the experimental condition to abstain more than those in the non-drinker control group. On other life functioning measures, however, subjects in the non-drinking experimental condition showed consistent improvement over their respective control subjects. Both of the controlled drinking groups reported more controlled drinking days than the non-drinking groups throughout the third year follow-up period.     

Comparative judgments with numerical reference points

A model of subjective magnitude comparisons is explored, which assumes that subjects compare symbolic stimulus magnitudes with respect to a reference point. The reference point may be established implicitly by the question (e.g., “Which is larger?” vs “Which is smaller?”) or be presented explicitly (e.g., “Choose the stimulus closer to X.”). The model was tested in five experiments in which subjects judged which of two comparison digits was closer to (or further from) a reference digit. Regression analyses in three experiments revealed that reaction time depended on the ratio of the distances from the comparison items to the reference point. The other two experiments provided evidence that subjects can strategically vary the processes by which they compare stimuli to a reference point. The results indicated that subjects can perform various types of “analog arithmetic” using either the linear number scale or a nonlinear scale of subjective digit magnitude.     

The interpretation of universal affirmative propositions

It is proposed that All F are G is often given a ‘structure-neutral’ interpretation, as All, F, G, lacking a subject-predicate distinction. In the first experiment, children aged 6–7–8, and 11–12, and adults, acted out instructions like “Make a building in which all the yellow blocks are square”. The experiment demonstrated the dominance in children and decline with age of structure-neutral interpretations. In a second experiment, with the same age groups, propositions of the form All F are G, varying as to the factual inclusion relations expressed, were presented as the major premises of syllogistic items. The results indicated the presence of structure-neutral interpretations under some circumstances in adults as well as children, and also demonstrated the existence in all subjects of a ‘pragmatic processing’ mode that becomes less obligatory with age. In pragmatic interpretations, meaning is determined by previously known factual relations between the things which the words represent, rather than by grammatical relations between the words themselves.     

Development of natural language concepts: IV. The relationship between semantic organization and learning

In Experiment 1, 30 subjects at each of three age levels were shown pictures of unfamiliar “animals”. They were told two semantic attributes for each animal (e.g., kind and strong) and were asked to learn these sets so that, when shown a picture, the appropriate attributes could be recalled. The results indicated that the dimensional structure of the attributes had a strong effect on new learning for young children. Incongruent pairs of attributes (e.g., kind and ugly) were difficult to learn compared to congruent (e.g., kind and beautiful) or unrelated (e.g., kind and tall) sets. These results indicate: (a) Attribute structure is a factor in new learning; (b) 6-year-olds tend to organize the verbal labels for attributes into bipolar dimensions, rather than into independent clusters of attributes. The latter findings require reexamination of the meaning of previous word-association data which had been interpreted as indicating that 6-year-olds tend not to organize meanings bipolarly. Experiment 2 showed that the disruptive effects of incongruence on new learning disappears by college age.     

The universal nature of human intelligence: Evidence from games

Mentally retarded individuals have relatively greater difficulty in dealing with strategic games and puzzles than with many other tasks. Consequently, it is of interest to find that strategic games have been played since ancient times, are played throughout the world, and that players who excel are frequently considered wise. Hidden within the more obvious differences between cultures, strategic games are an invariant expression of certain universal intellectual traits.