Distinctiveness and Correlation in Conceptual Structure: Behavioral and Computational Studies.

Patients with category-specific deficits have motivated a range of hypotheses about the structure of the conceptual system. One class of models claims that apparent category dissociations emerge from the internal structure of concepts rather than fractionation of the system into separate substores. This account claims that distinctive properties of concepts in the living domain are vulnerable because of their weak correlation with other features. Given the assumption that mutual activation among correlated properties produces faster activation in the normal system, the authors predicted a disadvantage for the distinctive features of living things for unimpaired adults. Results of a speeded feature verification study supported this prediction, as did a computational simulation in which networks mapped from orthography to semantics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bitwise Implementation of a Two-Dimensional Cellular Automata Biofilm Model

Mathematical modeling using the cellular automata (CA) approach is an attractive alternative to models based on partial differential equations when the domains to be simulated have complex boundary conditions. The computational efficiency of CA models is readily observed when using parallel processors, but implementations in personal computers are, although feasible, not quite efficient. In an effort to improve the computational efficiency of CA implementations in personal computers, we introduce in this paper a bitwise implementation based on the use of each bit as a different CA cell. Thus, in a 32-bit processor, each computer word stores information about 32 different CA cells. We illustrate the bitwise implementation with a biofilm model that simulates substrate diffusion and microbial growth of a single-species, single-substrate, structurally heterogeneous biofilm. The efficiency of the bitwise implementation was evaluated by comparing the computational time of equivalent CA biofilm models that used more common low-level implementations, namely, if-then operators and look-up tables. The processing speed of the bitwise implementation was over an order of magnitude higher than the processing speed of the other two implementations. Regarding the biofilm simulations, the CA model exhibited self-organization of the biofilm morphology as a function of kinetic and physical parameters.     

What is it like to be a patient with apperceptive agnosia?

Neuropsychological deficits have been widely used to elucidate normal cognitive functioning. Can patients with such deficits also be used to understand conscious visual experience? In this paper, we ask what it would be like to be a patient with apperceptive agnosia (a deficit in object recognition). Philosophical analyses of such questions have suggested that subjectively experiencing what another person experiences would be impossible. Although such roadblocks into the conscious experience of others exist, the experimental study of both patients and neurologically normal subjects can be used to understand visual processing mechanisms. In order to understand the visual processes damaged in apperceptive agnosia, we first review this syndrome and present a case study of one such patient, patient J.W. We then review several theoretical accounts of apperceptive agnosia, and we conclude that studies of the patients themselves may not allow us to discriminate between the various explanations of the syndrome. To test these accounts, we have simulated apperceptive agnosia in neurologically normal subjects. The implications of our results for understanding both apperceptive agnosia and normal visual processing are discussed.     

Psychological Processes Underlying Risky Decisions in Drug Abusers.

Decision-making deficits are considered to be a significant contributing factor for drug abuse. Drug abusers performed poorly on a simulated gambling task (A. Bechara, H. Damasio, D. Tranel, & S. Anderson, 1994); however, the psychological processes that contribute to these deficits are unknown. The authors used cognitive decision models with a simulated gambling task (SGT) to examine underlying processes of decision making in 66 drug abusers and 58 control participants. As expected, male drug abusers performed more poorly than male controls, and model results showed that male drug abusers placed greater emphasis on wins. The findings for women were less clear because control women performed at chance level on the SGT. Additional studies of gender differences on the SGT are needed to clarify these findings of discrepant performance in the control women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigations on Flow Pattern and Pressure inside SEN below Stopper Rod

In continuous casting of steel, the casting rate is often controlled by a stopper rod placed in the tundish outlet where the submerged entry nozzle (SEN) tube begins. The flow pattern inside the SEN plays an important role for the bubble formation at the argon injection nozzle at the stopper rod tip. High flow velocities are reached in the small gap between stopper rod and the surrounding SEN walls, and a flow separation has to be expected after the gap due to the fast expansion of the cross section. According to theoretical considerations and to the simulations, the absolute pressure in the gap becomes very low for liquid steel, which can cause cavitation‐like effects. PIV‐flow measurements in a 1:1 scaled water model of the caster show a highly oscillating and asymmetric flow pattern with rapidly changing separation regions. The low pressure effects expected in liquid steel cannot be investigated on the water‐model due to the lower density of water. In numerical simulations of the water‐model, the choice of the turbulence model and the usage or the non‐usage of geometrical symmetries for the bound of the computational domain have a great impact on the resulting flow pattern and the accuracy of the predicted pressure drop. The results of various turbulence models are compared with results from measurements on a water‐model. It turns out that only a 3D model using advanced turbulence models (SST k‐ω or Large Eddy) produce acceptable results, while 2D simulations completely fail and the standard turbulence models (e.g. k‐ε) significantly underestimate the pressure drop even in a 3D simulation.     

Testing Hypotheses Regarding the Causes of Comorbidity: Examining the Underlying Deficits of Comorbid Disorders.

The authors examined the validity of a method commonly used to test alternative hypotheses regarding the causes of comorbidity: the examination of underlying deficits of comorbid disorders. The authors simulated data in which the true causes of comorbidity were known, then compared the patterns of underlying deficits of the comorbid disorders found in the simulated data with the predicted results. The method of examining the underlying deficits of comorbid disorders could distinguish between several comorbidity models, including those that could not be distinguished well using other methods. The ability to distinguish the correct model decreased as the sample size and the correlation between the underlying deficits and the symptom scores decreased, suggesting that the issue of power should be considered carefully. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Rochester Symposium on Developmental Psychopathology, Volume 3: Models and integrations.

Reviews the book, Rochester Symposium on Developmental Psychopathology, Volume 3: Models and integrations by Dante Cicchetti and Sheree L. Toth (1991). Cicchetti and Toth's Models and integrations is the third of five volumes issuing from the annual "Rochester Symposium on Developmental Psychopathology," a series of publications which has served to define the discipline. The current volume plays a pivotal role in the evolution of developmental psychopathology because it raises important theoretical questions about the discipline, not the least of which are what is it and what might it be? In challenging the conceptual strength and clarity of the field, the book addresses salient developmental issues that will need to be resolved if the discipline is to advance. This is a thought-provoking and intellectually challenging book. It contains 11 weighty chapters organized into three relatively distinct but overlapping sections: (1) theoretical issues, (2) models for understanding specific forms of child psychopathology, and (3) developmentally-grounded intervention strategies. Each chapter in this book demonstrates an extraordinarily high level of theoretical and methodological sophistication. Collectively, the chapters in this volume constitute one of the most informative and sophisticated discussions of theory and methodology in the field of developmental psychopathology that is currently available. This volume is an outstanding contribution to the field and is highly recommended reading for advanced students and researchers in the areas of developmental and child psychopathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric Asymmetries in Cognitive Modeling: Connectionist Modeling of Unilateral Visual Neglect.

Neglect is an acquired cognitive disorder characterized by a lack of processing of one side of a stimulus or representational space. There are hemispheric asymmetries in its cause and in its effects, but implemented computational models of neglect have tended not to incorporate this fact. The authors report a series of neural network simulations of the line-bisection task. They test the hypothesis that simple, neuroanatomically realistic principles of connectivity in the nervous system can produce emergent behaviors that capture a wide range of quantitative and qualitative data observed in neglect patients presenting with general visuospatial neglect. They demonstrate that exploring low-level architectural principles in implemented computational models is both a productive avenue of research and offers the most parsimonious explanations of behaviors observed in patients. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Children with down syndrome: Implications for assessment and intervention in the school.

Down syndrome is the most common genetic cause of mental retardation and one of the most frequently occurring neurodevelopmental genetic disorders in children. Children with Down syndrome typically experience a constellation of symptomology that includes developmental motor and language delay, specific deficits in verbal memory, and broad cognitive deficits. Children with Down syndrome are also at increased risk of medical problems, which can exacerbate their cognitive deficits. Although the diagnosis of Down syndrome is facilitated by cytogenetic testing and the unique physical phenotype, the development of proper interventions for this group of children is less obvious. Despite their functional deficits, children with Down syndrome possess relative strengths, which can be the focus of interventions. This article reviews the etiology and developmental course of Down syndrome, appraises examples of empirically validated interventions, and discusses neurocognitive processing issues that should be considered during a psychoeducational evaluation for intervention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Growth curve models for indistinguishable dyads using multilevel modeling and structural equation modeling: The case of adolescent twins' conflict with their mothers.

Growth modeling is a useful tool for studying change over time, and it is becoming increasingly popular with developmental researchers. There is a considerable methodological literature surrounding growth modeling for individuals; however, far less attention has been focused on growth models for pairs of related individuals (i.e., dyads). In this article, the authors consider dyadic growth models for those cases where there are no relevant variables that can empirically distinguish between dyad members (e.g., same-sex twins or best friends). The authors describe how researchers can estimate growth models for indistinguishable dyads using both multilevel modeling and structural equation modeling. Although both approaches can be used to estimate the same underlying models, the authors focus on practical similarities and differences between the two approaches. They illustrate modeling issues using an overtime study of adolescent twins' conflict with their mothers, a substantively important topic given the enduring interest in parent-child relationships during adolescence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Grid-Enabled Simulation-Optimization Framework for Environmental Characterization

Many engineering and environmental problems that involve the determination of unknown system characteristics from observation data can be categorized as inverse problems. A common approach undertaken to solve such problems is the simulation-optimization approach where simulation models are coupled with optimization or search methods. Simulation-optimization approaches, particularly in environmental characterization involving natural systems, are computationally expensive due to the complex three-dimensional simulation models required to represent these systems and the large number of such simulations involved. Emerging grid computing environments (e.g., TeraGrid) show promise for improving the computational tractability of these approaches. However, harnessing grid resources for most computational applications is a nontrivial problem due to the complex hierarchy of heterogeneous and geographically distributed resources involved in a grid. This paper reports and discusses the development and evaluation of a grid-enabled simulation-optimization framework for solving environmental characterization problems. The framework is designed in a modular fashion that simplifies coupling with simulation model executables, allowing application of simulation-optimization approaches across problem domains. The framework architecture utilizes standard communications protocols and the message passing interface with an application programming interface to establish a connection between a centralized search application and simulation models running on TeraGrid resources. Sets of performance and scalability results for solving a groundwater source history reconstruction (SHR) problem are presented. The results show that for a given set of resources, parameters controlling the granularity at various levels of parallelism play an important role in the overall parallel performance. A production run for solving the SHR problem using three geographically distributed grid resources indicates that even in a cross-site grid environment a factor of 90 speedup is possible using 140 computer processors.     

Application of Piecewise Hierarchical Linear Growth Modeling to the Study of Continuity in Behavioral Development of Baboons (Papio hamadryas).

In behavioral science, developmental discontinuities are thought to arise when the association between an outcome measure and the underlying process changes over time. Sudden changes in behavior across time are often taken to indicate that a reorganization in the outcome-process relationship may have occurred. The authors proposed in this article the use of piecewise hierarchical linear growth modeling as a statistical methodology to search for discontinuities in behavioral development and illustrated its possibilities by applying 2-piece hierarchical linear models to the study of developmental trajectories of baboon (Papio hamadryas) mothers' behavior during their infants' 1st year of life. The authors provided empirical evidence that piecewise growth modeling can be used to determine whether abrupt changes in development trajectories are tied to changes in the underlying process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigation of Two- and Three-Dimensional Models of Transitional Flow Past a Square Cylinder

The present study is a comparison of two- and three-dimensional models of flow past a square cylinder at a Reynolds number of 250. The models are computational in nature. The governing equations have been solved by the Marker and Cell (MAC) method with higher order spatial and temporal discretization. Essential differences have been observed in the predictions of the two models. Results reveal that the rms values of the aerodynamic forces in the two-dimensional simulation are higher. These are related to higher stochastic fluctuations near the cylinder surface and a shorter spread of the fluctuating fields. The three-dimensional model shows a longer shear layer and the fluctuations are smaller. An interesting observation of the present study is that the fluctuations are the highest at the points of inflexion in the time-averaged velocity profile. The findings of the present study have been discussed with the help of physical reasoning along with the transport equations of velocity fluctuations.     

Assessing Psychological Change in Adulthood: An Overview of Methodological Issues.

This article reviews the current status of methods available for the analysis of psychological change in adulthood and aging. Enormous progress has been made in designing statistical models that can capture key aspects of intraindividual change, as reflected in techniques such as latent growth curve models and multilevel (random-effects) models. However, the rapid evolution of statistical innovations may have obscured the critical importance of addressing rival explanations for statistical outcomes, such as cohort differences or practice effects that could influence estimates of age-related change. Choice of modeling technique and implementation of a specific modeling approach should be grounded in and reflect both the theoretical nature of the developmental phenomenon and the features of the sampling design that selected persons, variables, and contexts for empirical observation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two-Dimensional Fast-Response Flood Modeling: Desktop Parallel Computing and Domain Tracking

Emergency flood management is enhanced by using models that can estimate the timing and location of flooding. Typically, flood routing and inundation prediction is accomplished by using one-dimensional (1D) models. These have been the models of choice because they are computationally simple and quick. However, these models do not adequately represent the complex physical processes present for shallow flows located in the floodplain or in urban areas. Two-dimensional (2D) models developed on the basis of the full hydrodynamic equations can be used to represent the complex flow phenomena that exist in the floodplain and are, therefore, recommended by the National Research Council for increased use in flood analysis studies. The major limitation of these models is the increased computational cost. Two-dimensional flood models are prime candidates for parallel computing, but traditional methods/equipment (e.g., message passing paradigm) are more complex in terms of code refactoring and hardware setup. In addition, these hardware systems may not be available or accessible to modelers conducting flood analyses. This paper presents a 2D flood model that implements multithreading for use on now-prevalent multicore computers. This desktop parallel computing architecture has been shown to decrease computation time by 14 times on a 16-processor computer and, when coupled with a wet cell tracking algorithm, has been shown to decrease computation by as much as 310 times. These accomplishments make high-fidelity flood modeling more feasible for flood inundation studies using readily available desktop computers.     

Phenotype of the tomato high pigment-2 mutant is caused by a mutation in the tomato homolog of DEETIOLATED1

Autism is a poorly understood developmental disorder characterized by social impairment, communication deficits, and compulsive behavior. The authors review evidence from animal studies demonstrating that the nonapeptides, oxytocin and vasopressin, have unique effects on the normal expression of species-typical social behavior, communication, and rituals. Based on this evidence, they hypothesize that an abnormality in oxytocin or vasopressin neurotransmission may account for several features of autism. As autism appears to be a genetic disorder, mutations in the various peptide, peptide receptor, or lineage-specific developmental genes could lead to altered oxytocin or vasopressin neurotransmission. Many of these genes have been cloned and sequenced, and several polymorphisms have been identified. Recent gene targeting studies that alter expression of either the peptides or their receptors in the rodent brain partially support the autism hypothesis. While previous experience suggests caution in hypothesizing a cause or suggesting a treatment for autism, the available preclinical evidence with oxytocin and vasopressin recommends the need for clinical studies using gene scanning, pharmacological and neurobiological approaches.     

A computational theory of executive cognitive processes and multiple-task performance: Part 2. Accounts of psychological refractory-period phenomena.

Further simulations of human multiple-task performance have been conducted with computational models that are based on the executive-process interactive control (EPIC) architecture introduced by D. E. Meyer and D. E. Kieras (see record 84-14604). These models account well for patterns of reaction times and psychological refractory-period phenomena (delays of overt responses after short stimulus onset asynchronies) observed in a variety of laboratory paradigms and realistic situations. This supports the claim of the present theoretical framework that multiple-task performance relies on adaptive executive control, which enables substantial amounts of temporal overlap among stimulus identification, response selection, and movement-production processes for concurrent tasks. Such overlap is achieved through optimized task scheduling by flexible executive processes that satisfy prevailing instructions about task priorities and allocate limited-capacity perceptual-motor resources efficiently. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Orwellian difference model.

Comments on the assertion by E. Zigler and W. Berman (see record 1984-07983-001) that the deficit model has given way to the difference model in early childhood intervention. It is suggested that models in science are ordinarily abandoned when they no longer describe empirical observations and that such is not the case in light of the financial and sociocultural deficits experienced by many children. It is concluded that Blacks should spurn the difference model; developmental psychologists may have embraced it because it is a way of avoiding a difficult complex of problems. (1 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Three-Dimensional Unsteady RANS Modeling of Discontinuous Gravity Currents in Rectangular Domains

Discontinuous gravity currents in rectangular channels are modeled numerically by solving the 3D unsteady Reynolds-averaged Navier-Stokes (URANS) equations closed with a buoyancy corrected low-Reynolds number (LRN) k-ε model using second-order accurate finite-volume numerics. It is shown that, on moderately fine computational meshes (with ～ 106 grid nodes) and with careful modeling of the near-wall flow, the URANS model can capture the essential large-scale 3D dynamics of gravity current flows, which previously had been resolved only by DNS and/or large-eddy simulation (LES) on very fine computational meshes. These 3D dynamics include the onset of the well-known lobe-and-cleft instability at the current head, the onset of large-scale Kelvin-Helmholtz billows at the head of the gravity current, and the breakdown of the interfacial billows in the rear part of the current head due to intense three-dimensional mixing. The computed results underscore the importance of careful modeling of the near wall flow in URANS simulations. The standard k-ε model with wall functions fails to capture the aforementioned complex 3D dynamics, which are only resolved by the LRN k-ε model on grids that resolve the near-wall region. Furthermore, numerical experiments show that including in the simulation the lateral no-slip end walls of the channel has a profound effect on the accuracy of the computed solutions. End-wall effects enhance the three-dimensionality of the flow, result in increased mixing of the dense and the ambient fluids behind the head of gravity currents, and yield results in good agreement with measurements. On the other hand, when end-wall effects are omitted, by imposing periodicity in the spanwise direction, three-dimensional mixing is suppressed and the breakdown of interfacial billows is significantly underestimated. Grid sensitivity studies are also carried out using three successively refined meshes and show that the URANS LRN model yields grid-converged solutions at affordable computational resources. As URANS modeling requires only a fraction of the computational cost of DNS or LES with near-wall resolution, the present results underscore the potential of unsteady statistical turbulence models for predicting and elucidating the physics of gravity current flows in complex geometries and at Reynolds numbers of engineering relevance.