The Effects Of Differential Reinforcement Structures On Computer-Assisted Instructional Learning

The use of computer assisted instruction as a viable educational technology in our nation\u27s schools has presented educators with new dilemmas and decisions. To operate these devices in the manner in which they were intended, computer software or courseware, whose cost often rivals the original cost of the computers themselves, must be purchased before their potential benefit can be realized. The most widely used type of instructional design that is inherent in these programs can be categorized under the operant theory of learning comprising the styles such as tutorial, skills building, and drill and practice. These computer lessons can be described as question-response-reinforcement in organizational design. The purpose of this study was to determine the nature of the reinforcement and its effects upon certain learner behaviors. Four computer lessons of equal length, scope and difficulty were designed to teach symbolic number systems to high school students. The lessons were designed with four different types of reinforcement structures ranging from sound and color graphics animation to simple knowledge of correct response. The programs were coded so that the students could control the real times allowed to read instructional frames, compute their responses, or watch the rewards. It was clear from the study that reinforcement style had little to do with the effectiveness of the lesson. Students watched the reinforcements for a substantial time to begin with, but ultimately opted to continue the program with little attention to the rewards. Students spent significantly more time watching the frames that demonstrated the question and correct response when they answered incorrectly than they spent listening or watching an animation intended for their delight. The implications for software publishers and purchasers are threefold: 1) Effort needs to be given in examination and evaluation of educational software concerning its learning design. 2) Programs designed as instructional tutorials should be structured economically, without the extensive reinforcement frills. 3) Continued research should be aimed at identifying the most efficient reinforcement strategies in operant-style computer assisted instruction

Consonant Context Effects on Vowel Sensorimotor Adaptation

Speech sensorimotor adaptation is the short-term learning of modified articulator movements evoked through sensory-feedback perturbations. A common experimental method manipulates acoustic parameters, such as formant frequencies, using real time resynthesis of the participant\u27s speech to perturb auditory feedback. While some studies have examined phrases comprised of vowels, diphthongs, and semivowels, the bulk of research on auditory feedback-driven sensorimotor adaptation has focused on vowels in neutral contexts (/hVd/). The current study investigates coarticulatory influences of adjacent consonants on sensorimotor adaptation. The purpose is to evaluate differences in the adaptation effects for vowels in consonant environments that vary by place and manner of articulation. In particular, we addressed the hypothesis that contexts with greater intra-articulator coarticulation and more static articulatory postures (alveolars and fricatives) offer greater resistance to vowel adaptation than contexts with primarily inter-articulator coarticulation and more dynamic articulatory patterns (bilabials and stops). Participants completed formant perturbation-driven vowel adaptation experiments for varying CVCs. Results from discrete formant measures at the vowel midpoint were generally consistent with the hypothesis. Analyses of more complete formant trajectories suggest that adaptation can also (or alternatively) influence formant onsets, offsets, and transitions, resulting in complex formant pattern changes that may reflect modifications to consonant articulatio

Estimating good discrete partitions from observed data: symbolic false nearest neighbors

A symbolic analysis of observed time series data requires making a discrete partition of a continuous state space containing observations of the dynamics. A particular kind of partition, called ``generating'', preserves all dynamical information of a deterministic map in the symbolic representation, but such partitions are not obvious beyond one dimension, and existing methods to find them require significant knowledge of the dynamical evolution operator or the spectrum of unstable periodic orbits. We introduce a statistic and algorithm to refine empirical partitions for symbolic state reconstruction. This method optimizes an essential property of a generating partition: avoiding topological degeneracies. It requires only the observed time series and is sensible even in the presence of noise when no truly generating partition is possible. Because of its resemblance to a geometrical statistic frequently used for reconstructing valid time-delay embeddings, we call the algorithm ``symbolic false nearest neighbors''

A Model for the Propagation of Sound in Granular Materials

This paper presents a simple ball-and-spring model for the propagation of small amplitude vibrations in a granular material. In this model, the positional disorder in the sample is ignored and the particles are placed on the vertices of a square lattice. The inter-particle forces are modeled as linear springs, with the only disorder in the system coming from a random distribution of spring constants. Despite its apparent simplicity, this model is able to reproduce the complex frequency response seen in measurements of sound propagation in a granular system. In order to understand this behavior, the role of the resonance modes of the system is investigated. Finally, this simple model is generalized to include relaxation behavior in the force network -- a behavior which is also seen in real granular materials. This model gives quantitative agreement with experimental observations of relaxation.Comment: 21 pages, requires Harvard macros (9/91), 12 postscript figures not included, HLRZ preprint 6/93, (replacement has proper references included

Inelastic collapse of a randomly forced particle

We consider a randomly forced particle moving in a finite region, which rebounds inelastically with coefficient of restitution r on collision with the boundaries. We show that there is a transition at a critical value of r, r_c\equiv e^{-\pi/\sqrt{3}}, above which the dynamics is ergodic but beneath which the particle undergoes inelastic collapse, coming to rest after an infinite number of collisions in a finite time. The value of r_c is argued to be independent of the size of the region or the presence of a viscous damping term in the equation of motion.Comment: 4 pages, REVTEX, 2 EPS figures, uses multicol.sty and epsf.st

The fossil record of early tetrapods: worker effort and the end-Permian mass extinction

It is important to understand the quality of the fossil record of early tetrapods (Tetrapoda, minus Lissamphibia and Amniota) because of their key role in the transition of vertebrates from water to land, their dominance of terrestrial faunas for over 100 million years of the late Palaeozoic and earlyMesozoic, and their variable fates during the end−Permian mass extinction. The first description of an early tetrapod dates back to 1824, and since then discoveries have occurred at a rather irregular pace, with peaks and troughs corresponding to some of the vicissitudes of human history through the past two centuries. As expected, the record is dominated by the well−sampled sedimentary basins of Europe and North America, but finds from other continents are increasing rapidly. Comparisons of snapshots of knowledge in 1900, 1950, and 2000 show that discovery of new species has changed the shape of the species−level diversification curve, contrary to earlier studies of family−level taxa. There is, however, little evidence that taxon counts relate to research effort (as counted by numbers of publications), and there are no biasing effects associated with differential study of different time intervals through the late Palaeozoic and Mesozoic. In fact, levels of effort are apparently not related to geological time, with no evidence that workers have spent more time on more recent parts of the record. In particular, the end−Permian mass extinction was investigated to determine whether diversity changes through that interval might reflect worker effort: it turns out that most records of early tetrapod taxa (when corrected for duration of geological series) occur in the Lower Triassic

Some , And Possibly All, Scalar Inferences Are Not Delayed: Evidence For Immediate Pragmatic Enrichment

Scalar inferences are commonly generated when a speaker uses a weaker expression rather than a stronger alternative, e.g., John ate some of the apples implies that he did not eat them all. This article describes a visual-world study investigating how and when perceivers compute these inferences. Participants followed spoken instructions containing the scalar quantifier some directing them to interact with one of several referential targets (e.g., Click on the girl who has some of the balloons). Participants fixated on the target compatible with the implicated meaning of some and avoided a competitor compatible with the literal meaning prior to a disambiguating noun. Further, convergence on the target was as fast for some as for the non-scalar quantifiers none and all. These findings indicate that the scalar inference is computed immediately and is not delayed relative to the literal interpretation of some. It is argued that previous demonstrations that scalar inferences increase processing time are not necessarily due to delays in generating the inference itself, but rather arise because integrating the interpretation of the inference with relevant information in the context may require additional time. With sufficient contextual support, processing delays disappear

Gene Circuit Analysis of the Terminal Gap Gene huckebein

The early embryo of Drosophila melanogaster provides a powerful model system to study the role of genes in pattern formation. The gap gene network constitutes the first zygotic regulatory tier in the hierarchy of the segmentation genes involved in specifying the position of body segments. Here, we use an integrative, systems-level approach to investigate the regulatory effect of the terminal gap gene huckebein (hkb) on gap gene expression. We present quantitative expression data for the Hkb protein, which enable us to include hkb in gap gene circuit models. Gap gene circuits are mathematical models of gene networks used as computational tools to extract regulatory information from spatial expression data. This is achieved by fitting the model to gap gene expression patterns, in order to obtain estimates for regulatory parameters which predict a specific network topology. We show how considering variability in the data combined with analysis of parameter determinability significantly improves the biological relevance and consistency of the approach. Our models are in agreement with earlier results, which they extend in two important respects: First, we show that Hkb is involved in the regulation of the posterior hunchback (hb) domain, but does not have any other essential function. Specifically, Hkb is required for the anterior shift in the posterior border of this domain, which is now reproduced correctly in our models. Second, gap gene circuits presented here are able to reproduce mutants of terminal gap genes, while previously published models were unable to reproduce any null mutants correctly. As a consequence, our models now capture the expression dynamics of all posterior gap genes and some variational properties of the system correctly. This is an important step towards a better, quantitative understanding of the developmental and evolutionary dynamics of the gap gene network

Radio Astronomy

Contains reports on five research projects.National Science Foundation (Grant AST82-14296)National Aeronautics and Space Administration (Grant NAG W-373)National Aeronautics and Space Administration (Grant NAG5-537)U.S. Navy - Office of Naval Research (Contract N00014-84-C-2082)SM Systems and Research, Inc.Defense Advanced Research Project Agency (Contract MDA903-82-K-0521