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1.
A latent class vector model for preference ratings 总被引:1,自引:1,他引:1
A latent class formulation of the well-known vector model for preference data is presented. Assuming preference ratings as
input data, the model simultaneously clusters the subjects into a small number of homogeneous groups (or latent classes) and
constructs a joint geometric representation of the choice objects and the latent classes according to a vector model. The
distributional assumptions on which the latent class approach is based are analogous to the distributional assumptions that
are consistent with the common practice of fitting the vector model to preference data by least squares methods. An EM algorithm
for fitting the latent class vector model is described as well as a procedure for selecting the appropriate number of classes
and the appropriate number of dimensions. Some illustrative applications of the latent class vector model are presented and
some possible extensions are discussed.
Geert De Soete is supported as “Bevoegdverklaard Navorser” of the Belgian “Nationaal Fonds voor Wetenschappelijk Onderzoek.” 相似文献
2.
The issue of determining “the right number of clusters” in K-Means has attracted considerable interest, especially in the
recent years. Cluster intermix appears to be a factor most affecting the clustering results. This paper proposes an experimental
setting for comparison of different approaches at data generated from Gaussian clusters with the controlled parameters of
between- and within-cluster spread to model cluster intermix. The setting allows for evaluating the centroid recovery on par
with conventional evaluation of the cluster recovery. The subjects of our interest are two versions of the “intelligent” K-Means method, ik-Means, that find the “right” number of clusters by extracting “anomalous patterns” from the data one-by-one. We compare them
with seven other methods, including Hartigan’s rule, averaged Silhouette width and Gap statistic, under different between-
and within-cluster spread-shape conditions. There are several consistent patterns in the results of our experiments, such
as that the right K is reproduced best by Hartigan’s rule – but not clusters or their centroids. This leads us to propose an adjusted version
of iK-Means, which performs well in the current experiment setting. 相似文献
3.
A modified CANDECOMP algorithm is presented for fitting the metric version of the Extended INDSCAL model to three-way proximity
data. The Extended INDSCAL model assumes, in addition to the common dimensions, a unique dimension for each object. The modified
CANDECOMP algorithm fits the Extended INDSCAL model in a dimension-wise fashion and ensures that the subject weights for the
common and the unique dimensions are nonnegative. A Monte Carlo study is reported to illustrate that the method is fairly
insensitive to the choice of the initial parameter estimates. A second Monte Carlo study shows that the method is able to
recover an underlying Extended INDSCAL structure if present in the data. Finally, the method is applied for illustrative purposes
to some empirical data on pain relievers. In the final section, some other possible uses of the new method are discussed.
Geert De Soete is supported as “Bevoegdverklaard Navorser” of the Belgian “Nationaal Fonds voor Wetenschappelijik Onderzoek”. 相似文献
4.
Stephen Palmquist 《Foundations of Science》2007,12(1):9-37
After sketching the historical development of “emergence” and noting several recent problems relating to “emergent properties”,
this essay proposes that properties may be either “emergent” or “mergent” and either “intrinsic” or “extrinsic”. These two
distinctions define four basic types of change: stagnation, permanence, flux, and evolution. To illustrate how emergence can
operate in a purely logical system, the Geometry of Logic is introduced. This new method of analyzing conceptual systems involves
the mapping of logical relations onto geometrical figures, following either an analytic or a synthetic pattern (or both together).
Evolution is portrayed as a form of discontinuous change characterized by emergent properties that take on an intrinsic quality
with respect to the object(s) or proposition(s) involved. Causal leaps, not continuous development, characterize the evolution
of human life in a developing foetus, of a thought out of certain brain states, of a new idea (or insight) out of ordinary
thoughts, and of a great person out of a set of historical experiences. The tendency to assume that understanding evolutionary
change requires a step-by-step explanation of the historical development that led to the appearance of a certain emergent
property is thereby discredited. 相似文献
5.
Franc Rottiers 《Foundations of Science》2012,17(1):39-41
The aim of this contribution is to critically examine the metaphysical presuppositions that prevail in (Stewart in Found Sci
15(4):395–409, 2010a) answer to the question “are we in the midst of a developmental process?” as expressed in his statement “that humanity has
discovered the trajectory of past evolution and can see how it is likely to continue in the future”. 相似文献
6.
Wojtek J. Krzanowski Trevor C. Bailey Derek Partridge Jonathan E. Fieldsend Richard M. Everson Vitaly Schetinin 《Journal of Classification》2006,23(2):199-220
Bayesian classification is currently of considerable interest. It provides a strategy for eliminating the uncertainty associated
with a particular choice of classifiermodel parameters, and is the optimal decision-theoretic choice under certain circumstances
when there is no single “true” classifier for a given data set. Modern computing capabilities can easily support the Markov
chain Monte Carlo sampling that is necessary to carry out the calculations involved, but the information available in these
samples is not at present being fully utilised. We show how it can be allied to known results concerning the “reject option”
in order to produce an assessment of the confidence that can be ascribed to particular classifications, and how these confidence
measures can be used to compare the performances of classifiers. Incorporating these confidence measures can alter the apparent
ranking of classifiers as given by straightforward success or error rates. Several possible methods for obtaining confidence
assessments are described, and compared on a range of data sets using the Bayesian probabilistic nearest-neighbour classifier. 相似文献
7.
Brigitte Cambon de Lavalette Charles Tijus Christine Leproux Olivier Bauer 《Foundations of Science》2005,10(1):25-45
Taxonomy Based modeling was applied to describe drivers’ mental models of variable message signs (VMS’s) displayed on expressways.
Progress in road telematics has made it possible to introduce variable message signs (VMS’s). Sensors embedded in the carriageway
every 500m record certain variables (speed, flow rate, etc.) that are transformed in real time into “driving times” to a given
destination if road conditions do not change.
VMS systems are auto-regulative Man-Machine (AMMI) systems which incorporate a model of the user: if the traffic flow is too
high, then drivers should choose alternative routes. In so doing, the traffic flow should decrease. The model of the user
is based on suppositions such as: people do not like to waste time, they fully understand the displayed messages, they trust
the displayed values, they know of alternative routes. However, people also have a model of the way the system functions.
And if they do not believe the contents of the message, they will not act as expected.
We collected data through interviews with drivers using the critical incidents technique (Flanagan, 1985). Results show that
the mental models that drivers have of the way the VMS system works are various but not numerous and that most of them differ
from the“ideal expert” mental model. It is clear that users don’t have an adequate model of how the VMS system works and that
VMS planners have a model of user behaviour that does not correspond to the behaviour of the drivers we interviewed. Finally,
Taxonomy Based Modeling is discussed as a tool for mental model remediation. 相似文献
8.
Towards a Hierarchical Definition of Life,the Organism,and Death 总被引:3,自引:3,他引:0
Gerard A. J. M. Jagers op Akkerhuis 《Foundations of Science》2010,15(3):245-262
Despite hundreds of definitions, no consensus exists on a definition of life or on the closely related and problematic definitions
of the organism and death. These problems retard practical and theoretical development in, for example, exobiology, artificial
life, biology and evolution. This paper suggests improving this situation by basing definitions on a theory of a generalized
particle hierarchy. This theory uses the common denominator of the “operator” for a unified ranking of both particles and
organisms, from elementary particles to animals with brains. Accordingly, this ranking is called “the operator hierarchy”.
This hierarchy allows life to be defined as: matter with the configuration of an operator, and that possesses a complexity
equal to, or even higher than the cellular operator. Living is then synonymous with the dynamics of such operators and the
word organism refers to a select group of operators that fit the definition of life. The minimum condition defining an organism
is its existence as an operator, construction thus being more essential than metabolism, growth or reproduction. In the operator
hierarchy, every organism is associated with a specific closure, for example, the nucleus in eukaryotes. This allows death
to be defined as: the state in which an organism has lost its closure following irreversible deterioration of its organization.
The generality of the operator hierarchy also offers a context to discuss “life as we do not know it”. The paper ends with
testing the definition’s practical value with a range of examples. 相似文献
9.
Melvin S. Steinberg 《Foundations of Science》2008,13(2):163-175
Investigations with electrometers in the 1770s led Volta to envision mobile charge in electrical conductors as a compressible
fluid. A pressure-like condition in this fluid, which Volta described as the fluid’s “effort to push itself out” of its conducting
container, was the causal agent that makes the fluid move. In this paper I discuss Volta’s use of analogy and imagery in model
building, and compare with a successful contemporary conceptual approach to introducing ideas about electric potential in
instruction. The concept that today is called “electric potential” was defined mathematically by Poisson in 1811. It was understood
after about 1850 to predict the same results in conducting matter as Volta’s pressure-like concept—and to predict electrostatic
effects in the exterior space where Volta’s concept had nothing to say. Complete quantification in addition to greater generality
made the mathematical concept a superior research tool for scientists. However, its spreading use in instruction has marginalized
approaches to model building based on the analogy and imagery resources that students bring into the classroom. Data from
pre and post testing in high schools show greater conceptual and confidence gains using the new conceptual approach than using
conventional instruction. This provides evidence for reviving Volta’s compressible fluid model as an intuitive foundation
which can then be modified to include electrostatic distant action. Volta tried to modify his compressible fluid model to
include distant action, using imagery borrowed from distant heating by a flame. This project remained incomplete, because
he did not envision an external field mediating the heating. However, pursuing Volta’s strategy of model modification to completion
now enables students taught with the new conceptual approach to add distant action to an initial compressible fluid model.
I suggest that a partial correspondence to the evolving model sequence that works for beginning students can help illuminate
Volta’s use of intermediate explanatory models.
相似文献
Melvin S. SteinbergEmail: |
10.
The Self-Organization of Time and Causality: Steps Towards Understanding the Ultimate Origin 总被引:2,自引:2,他引:0
Francis Heylighen 《Foundations of Science》2010,15(4):345-356
Possibly the most fundamental scientific problem is the origin of time and causality. The inherent difficulty is that all
scientific theories of origins and evolution consider the existence of time and causality as given. We tackle this problem
by starting from the concept of self-organization, which is seen as the spontaneous emergence of order out of primordial chaos.
Self-organization can be explained by the selective retention of invariant or consistent variations, implying a breaking of
the initial symmetry exhibited by randomness. In the case of time, we start from a random graph connecting primitive “events”.
Selection on the basis of consistency eliminates cyclic parts of the graph, so that transitive closure can transform it into
a partial order relation of precedence. Causality is assumed to be carried by causal “agents” which undergo a more traditional
variation and selection, giving rise to causal laws that are partly contingent, partly necessary. 相似文献
11.
A clustering that consists of a nested set of clusters may be represented graphically by a tree. In contrast, a clustering
that includes non-nested overlapping clusters (sometimes termed a “nonhierarchical” clustering) cannot be represented by a
tree. Graphical representations of such non-nested overlapping clusterings are usually complex and difficult to interpret.
Carroll and Pruzansky (1975, 1980) suggested representing non-nested clusterings with multiple ultrametric or additive trees.
Corter and Tversky (1986) introduced the extended tree (EXTREE) model, which represents a non-nested structure as a tree plus
overlapping clusters that are represented by marked segments in the tree. We show here that the problem of finding a nested
(i.e., tree-structured) set of clusters in an overlapping clustering can be reformulated as the problem of finding a clique
in a graph. Thus, clique-finding algorithms can be used to identify sets of clusters in the solution that can be represented
by trees. This formulation provides a means of automatically constructing a multiple tree or extended tree representation
of any non-nested clustering. The method, called “clustrees”, is applied to several non-nested overlapping clusterings derived
using the MAPCLUS program (Arabie and Carroll 1980). 相似文献
12.
Ivan M. Havel 《Foundations of Science》1998,3(2):375-394
Certain cognitive and philosophical aspects of the concept of conceivability with intended or established diversion from (putative)
reality are discussed. The “coherence gap problem” arises when certain fragments of the real world are replaced with imaginary
situations while most details are (intentionally or not) ignored. Another issue, “the spectator problem”, concerns the participation
of the conceiver himself in the world conceived. Three different examples of conceivability are used to illustrate our points,
namely thought experiments in physics, a hypothetical world devoid of consciousness (zombie world), and virtual reality.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Dan Mcarthur 《Foundations of Science》2006,11(4):369-397
In recent years a general consensus has been developing in the philosophy of science to the effect that strong social constructivist
accounts are unable to adequately account for scientific practice. Recently, however, a number of commentators have formulated
an attenuated version of constructivism that purports to avoid the difficulties that plague the stronger claims of its predecessors.
Interestingly this attenuated form of constructivism finds philosophical support from a relatively recent turn in the literature
concerning scientific realism. Arthur Fine and a number of other commentators have argued that the realism debate ought to
be abandoned. The rationale for this argument is that the debate is sterile for it has, it is claimed, no consequence for
actual scientific practice, and therefore does not advance our understanding of science or its practice. Recent “softer” accounts
of social constructivism also hold a similar agnostic stance to the realism question. I provide a survey of these various
agnostic stances and show how they form a general position that I shall refer to as “the anti-philosophical stance”. I then
demonstrate that the anti-philosophical stance fails by identifying difficulties that attend its proposal to ban philosophical
interpretation. I also provide examples of instances where philosophical stances to the realism question affect scientific
practice. 相似文献
14.
Pierre Uzan 《Foundations of Science》2007,12(2):109-137
All the attempts to find the justification of the privileged evolution of phenomena exclusively in the external world need
to refer to the inescapable fact that we are living in such an asymmetric universe. This leads us to look for the origin of the “arrow of time” in the relationship
between the subject and the world. The anthropic argument shows that the arrow of time is the condition of the possibility
of emergence and maintenance of life in the universe. Moreover, according to Bohr’s, Poincaré’s and Watanabe’s analysis, this
agreement between the earlier-later direction of entropy increase and the past-future direction of life is the very condition
of the possibility for meaningful action, representation and creation. Beyond this relationship of logical necessity between
the meaning process and the arrow of time the question of their possible physical connection is explored. To answer affirmatively
to this question, the meaning process is modelled as an evolving tree-like structure, called “Semantic Time”, where thermodynamic
irreversibility can be shown.
Time is the substance I am made of. Time is a river which sweeps me along, but I am the river ; it is a tiger which destroys
me, but I am the tiger ; it is a fire which consumes me, but I am the fire. – (Jorge Luis Borges) 相似文献
15.
John J. Sung 《Foundations of Science》2008,13(2):177-193
Scientific anomalies are observations and facts that contradict current scientific theories and they are instrumental in scientific
theory change. Philosophers of science have approached scientific theory change from different perspectives as Darden (Theory
change in science: Strategies from Mendelian genetics, 1991) observes: Lakatos (In: Lakatos, Musgrave (eds) Criticism and
the growth of knowledge, 1970) approaches it as a progressive “research programmes” consisting of incremental improvements
(“monster barring” in Lakatos, Proofs and refutations: The logic of mathematical discovery, 1976), Kuhn (The structure of
scientific revolutions, 1996) observes that changes in “paradigms” are instigated by a crisis from some anomaly, and Hanson
(In: Feigl, Maxwell (eds) Current issues in the philosophy of science, 1961) proposes that discovery does not begin with hypothesis
but with some “problematic phenomena requiring explanation”. Even though anomalies are important in all of these approaches
to scientific theory change, there have been only few investigations into the specific role anomalies play in scientific theory
change. Furthermore, much of these approaches focus on the theories themselves and not on how the scientists and their experiments
bring about scientific change (Gooding, Experiment and the making of meaning: Human agency in scientific observation and experiment,
1990). To address these issues, this paper approaches scientific anomaly resolution from a meaning construction point of view.
Conceptual integration theory (Fauconnier and Turner, Cogn Sci 22:133–187, 1996; The way we think: Conceptual blending and
mind’s hidden complexities, 2002) from cognitive linguistics describes how one constructs meaning from various stimuli, such
as text and diagrams, through conceptual integration or blending. The conceptual integration networks that describe the conceptual
integration process characterize cognition that occurs unconsciously during meaning construction. These same networks are
used to describe some of the cognition while resolving an anomaly in molecular genetics called RNA interference (RNAi) in
a case study. The RNAi case study is a cognitive-historical reconstruction (Nersessian, In: Giere (ed) Cognitive models of
science, 1992) that reconstructs how the RNAi anomaly was resolved. This reconstruction traces four relevant molecular genetics
publications in describing the cognition necessary in accounting for how RNAi was resolved through strategies (Darden 1991),
abductive reasoning (Peirce, In: Hartshorne, Weiss (eds) Collected papers, 1958), and experimental reasoning (Gooding 1990).
The results of the case study show that experiments play a crucial role in formulating an explanation of the RNAi anomaly
and the integration networks describe the experiments’ role. Furthermore, these results suggest that RNAi anomaly resolution
is embodied. It is embodied in a sense that cognition described in the cognitive-historical reconstruction is experientially
based.
相似文献
John J. SungEmail: |
16.
György Darvas 《Foundations of Science》2009,14(4):273-280
Attemts to explain causal paradoxes of Quantum Mechanics (QM) have tried to solve the problems within the framework of Quantum
Electrodynamics (QED). We will show, that this is impossible. The original theory of QED by Dirac (Proc Roy Soc A117:610,
1928) formulated in its preamble four preliminary requirements that the new theory should meet. The first of these requirements
was that the theory must be causal. Causality is not to be derived as a consequence of the theory since it was a precondition
for the formulation of the theory; it has been constructed so that it be causal. Therefore, causal paradoxes logically cannot
be explained within the framework of QED. To transcend this problem we should consider the following points: Dirac himself
stated in his original paper (1928) that his theory was only an approximation. When he returned to improve the theory later
(Proc Roy Soc A209, 1951), he noted that the new theory “involves only the ratio e/m, not e and m separately”. This is a sign that although the electromagnetic effects (whose source is e) are magnitudes stronger than the gravitational effects (whose source is m), the two are coupled. Already in 1919, Einstein noted that “the elementary formations which go to make up the atom” are
influenced by gravitational forces. Although in that form the statement proved not to be exactly correct, the effects of gravitation
on QM phenomena have been established. The conclusion is that we should seek a resolution for the causal paradoxes in the
framework of the General Theory of Relativity (GTR)—in contrast to QED, which involves only the Special Theory of Relativity
(STR). We show that causality is necessarily violated in GTR. This follows from the curvature of the space-time. Although
those effects are very small, one cannot ignore their influence in the case of the so-called “paradox phenomena”. 相似文献
17.
Andreas Dress Katharina T. Huber Jacobus Koolen Vincent Moulton Andreas Spillner 《Journal of Classification》2010,27(2):158-172
The theory of the tight span, a cell complex that can be associated to every metric D, offers a unifying view on existing approaches for analyzing distance data, in particular for decomposing a metric D into a sum of simpler metrics as well as for representing it by certain specific edge-weighted graphs, often referred to
as realizations of D. Many of these approaches involve the explicit or implicit computation of the so-called cutpoints of (the tight span of)
D, such as the algorithm for computing the “building blocks” of optimal realizations of D recently presented by A. Hertz and S. Varone. The main result of this paper is an algorithm for computing the set of these
cutpoints for a metric D on a finite set with n elements in O(n3) time. As a direct consequence, this improves the run time of the aforementioned O(n6)-algorithm by Hertz and Varone by “three orders of magnitude”. 相似文献
18.
Pierre Uzan 《Foundations of Science》2010,15(1):1-28
This paper suggests an epistemic interpretation of Belnap’s branching space-times theory based on Everett’s relative state
formulation of the measurement operation in quantum mechanics. The informational branching models of the universe are evolving
structures defined from a partial ordering relation on the set of memory states of the impersonal observer. The totally ordered
set of their information contents defines a linear “time” scale to which the decoherent alternative histories of the informational
universe can be referred—which is quite necessary for assigning them a probability distribution. The “historical” state of
a physical system is represented in an appropriate extended Hilbert space and an algebra of multi-branch operators is developed.
An age operator computes the informational depth of historical states and its standard deviation can be used to provide a
universal information/energy uncertainty relation. An information operator computes the encoding complexity of historical
states, the rate of change of its average value accounting for the process of correlation destruction inherent to the branching
dynamics. In the informational branching models of the universe, the asymmetry of phenomena in nature appears as a mere consequence
of the subject’s activity of measuring, which defines the flow of time-information. 相似文献
19.
A common practice in cross validation research in the behavioral sciences is to employ either the product moment correlation
or a simple tabulation of first-choice “hits” for measuring the accuracy with which various preference models predict subjects’
responses to a holdout sample of choice objects.
We propose a nonparametric approach for summarizing the accuracy of predicted rankings across a set of holdout-sample options.
The methods that we develop contain a novel way to deal with ties and an approach to the different weighting of rank positions. 相似文献
20.
Clément Vidal 《Foundations of Science》2012,17(1):29-38
Jan Greben criticized fine-tuning by taking seriously the idea that “nature is quantum mechanical”. I argue that this quantum
view is limited, and that fine-tuning is real, in the sense that our current physical models require fine-tuning. Second,
I examine and clarify many difficult and fundamental issues raised by Rüdiger Vaas’ comments on Cosmological Artificial Selection. 相似文献