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141.
Yamaguchi M 《Scandinavian journal of psychology》2004,45(5):357-361
Connectionist models with a backpropagation learning rule are known to have a serious problem. Such models exhibit catastrophic interference (or forgetting) with sequential training. Having learned a set of patterns, if the model is trained on another set of patterns, its performance on the first set can dramatically deteriorate very rapidly. The present study reconsiders this issue with four simulations. The model learned arithmetic facts sequentially, but the interference was only modest with random (hence approximately orthogonal) inputs. Essentially the same result was obtained when the inputs are made less orthogonal by adding irrelevant elements. Reducing the number of hidden units did not have major effects. This study suggests that the interference problem has been somewhat overstated. 相似文献
142.
The problem of constructing computational models of space that mimic those found in human spatial reasoning is addressed. This paper extends a formal model that addressed point objects in a 2D world to include the presence of line objects and barriers. The problem consists of determining an appropriate global model for the spatial configuration given a sequence of local views or observations. A formal model is proposed based on constraint network theory. The model leads to the identification of stable regions within which perceptual information about the environment changes slowly, and zones of transition within which the perceptual information changes more quickly. A special case of transition zones is a gateway, which may be viewed as a kind of discontinuity or singularity in the model. It is expected that the model obtained will be used to mimic human mental representations of navigable outdoor environments. 相似文献
143.
144.
Recently, it has been recognized that the commonly used linear structural equation model is inadequate to deal with some complicated substantive theory. A new nonlinear structural equation model with fixed covariates is proposed in this article. A procedure, which utilizes the powerful path sampling for computing the Bayes factor, is developed for model comparison. In the implementation, the required random observations are simulated via a hybrid algorithm that combines the Gibbs sampler and the Metropolis-Hastings algorithm. It is shown that the proposed procedure is efficient and flexible; and it produces Bayesian estimates of the parameters, latent variables, and their highest posterior density intervals as by-products. Empirical performances of the proposed procedure such as sensitivity to prior inputs are illustrated by a simulation study and a real example.This research is fully supported by a grant from the Research Grant Council of the Hong Kong Special Administrative Region, China (Project No. CUHK 4346/01H). The authors are thankful to the Editor, the Associate Editor, and anonymous reviewers for valuable comments which improve the paper significantly, and grateful to ICPSR and the relevant funding agency for allowing use of the data in the example. The assistance of Michael K.H. Leung and Esther L.S. Tam is gratefully acknowledged. 相似文献
145.
A person-fit index for polytomous rasch models,latent class models,and their mixture generalizations
A normally distributed person-fit index is proposed for detecting aberrant response patterns in latent class models and mixture distribution IRT models for dichotomous and polytomous data.This article extends previous work on the null distribution of person-fit indices for the dichotomous Rasch model to a number of models for categorical data. A comparison of two different approaches to handle the skewness of the person-fit index distribution is included.Major parts of this paper were written while the first author worked at the Institute for Science Education, Kiel, Germany. Any opinions expressed in this paper are those of the authors and not necessarily of Educational Testing Service. The results presented in this paper were improved by valuable comments from J. Rost, K. Yamamoto, N.D. Verhelst, E. Bedrick and two anonymous reviewers. 相似文献
146.
Ross LF 《Theoretical medicine and bioethics》2003,24(2):177-197
There are approximately one million cases oftype 1 diabetes in the US, and the incidenceis increasing worldwide. Given that two-thirdsof cases present in childhood, it is criticalthat prediction and prevention research involvechildren. In this article, I examine whethercurrent research methodologies conform to theethical guidelines enumerated by the NationalCommission for the Protection of Human Subjectsof Biomedical and Behavioral Research, andadopted into the federal regulations thatprotect research subjects. I then offer twopolicy recommendations to help researchersdesign studies that conform to these ethicalrequirements. 相似文献
147.
This essay explores the role of informal logicand its application in the context of currentdebates regarding evidence-based medicine. This aim is achieved through a discussion ofthe goals and objectives of evidence-basedmedicine and a review of the criticisms raisedagainst evidence-based medicine. Thecontributions to informal logic by StephenToulmin and Douglas Walton are explicated andtheir relevance for evidence-based medicine isdiscussed in relation to a common clinicalscenario: hypertension management. This essayconcludes with a discussion on the relationshipbetween clinical reasoning, rationality, andevidence. It is argued that informal logic hasthe virtue of bringing explicitness to the roleof evidence in clinical reasoning, and bringssensitivity to understanding the role ofdialogical context in the need for evidence inclinical decision making. 相似文献
148.
This paper concerns items that consist of several item steps to be responded to sequentially. The item scoreX is defined as the number of correct responses until the first failure. Samejima's graded response model states that each steph=1,...,m is characterized by a parameterb
h
, and, for a subject with ability, Pr(Xh; )=F(–b
h
). Tutz's general sequential model associates with each step a parameterdh, and it states that Pr(Xh;)=
r
=1h
G(–d
r
). Tutz's (1991, 1997) conjectures that the models are equivalent if and only ifF(x)=G(x) is an extreme value distribution. This paper presents a proof for this conjecture. 相似文献
149.
Evans M 《Theoretical medicine and bioethics》2001,22(1):17-32
Medicine, as Byron Good argues, reconstitutes thehuman body of our daily experience as a medical body,unfamiliar outside medicine. This reconstitution can be seen intwo ways: (i) as a salutary reminder of the extent to which thereality even of the human body is constructed; and (ii) as anarena for what Stephen Toulmin distinguishes as theintersection of natural science and history, in which many ofphilosophy's traditional (and traditionally abstract) questionsare given concrete and urgent form.This paper begins by examining a number of dualities between themedical body and the body familiar in daily experience. Toulmin's epistemological analysis of clinical medicine ascombining both universal and existential knowledge is thenconsidered. Their expression, in terms of attention,respectively, to natural science and to personal history, isexplored through the epistemological contrasts between themedical body and the familiar body, noting the traditionalphilosophical questions which they in turn illustrate. 相似文献
150.