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Causal Structure (causal + structure)
Selected AbstractsHow fantasy benefits young children's understanding of pretenseDEVELOPMENTAL SCIENCE, Issue 1 2006David M. Sobel Sobel and Lillard (2001) demonstrated that 4-year-olds' understanding of the role that the mind plays in pretending improved when children were asked questions in a fantasy context. The present study investigated whether this fantasy effect was motivated by children recognizing that fantasy contains violations of real-world causal structure. In Experiment 1, 4-year-olds were shown a fantasy character engaged in ordinary actions or actions that violated causal knowledge. Children were more likely to say that a troll doll who was acting like but ignorant of the character was not pretending to be that character when read the violation story. Experiment 2 suggested that this difference was not caused by a greater interest in the violation story. Experiment 3 demonstrated a similar difference for characters engaged in social and functional violations that were possible in the real world. These data are consistent with the hypothesis that preschoolers use actions and appearance more than mental states to make judgments about pretense, but that those judgments can be influenced by the context in which the questions are presented. [source] Testing effective connectivity changes with structural equation modeling: What does a bad model tell us?HUMAN BRAIN MAPPING, Issue 12 2006Andrea B. Protzner Abstract Structural equation modeling (SEM) is a statistical method that can assess changes in effective connectivity across tasks or between groups. In its initial application to neuroimaging data, anatomical connectivity provided the constraints to decompose interregional covariances to estimate effective connections. There have been concerns expressed, however, with the validity of interpreting effective connections for a model that does not adequately fit the data. We sought to address this concern by creating two population networks with different patterns of effective connectivity, extracting three samples sizes (N = 100, 60, 20), and then assessing whether the ability to detect effective connectivity differences depended on absolute model fit. Four scenarios were assessed: (1) elimination of a region showing no task differences; (2) elimination of connections with no task differences; (3) elimination of connections that carried task differences, but could be expressed through alternative indirect routes; (4) elimination of connections that carried task differences, and could not be expressed through indirect routes. We were able to detect task differences in all four cases, despite poor absolute model fit. In scenario 3, total effects captured the overall task differences even though the direct effect was no longer present. In scenario 4, task differences that were included in the model remained, but the missing effect was not expressed. In conclusion, it seems that when independent information (e.g., anatomical connectivity) is used to define the causal structure in SEM, inferences about task- or group-dependent changes are valid regardless of absolute model fit. Hum Brain Mapp, 2006. © 2006 Wiley-Liss, Inc. [source] Forecast covariances in the linear multiregression dynamic modelJOURNAL OF FORECASTING, Issue 2 2008Catriona M. Queen Abstract The linear multiregression dynamic model (LMDM) is a Bayesian dynamic model which preserves any conditional independence and causal structure across a multivariate time series. The conditional independence structure is used to model the multivariate series by separate (conditional) univariate dynamic linear models, where each series has contemporaneous variables as regressors in its model. Calculating the forecast covariance matrix (which is required for calculating forecast variances in the LMDM) is not always straightforward in its current formulation. In this paper we introduce a simple algebraic form for calculating LMDM forecast covariances. Calculation of the covariance between model regression components can also be useful and we shall present a simple algebraic method for calculating these component covariances. In the LMDM formulation, certain pairs of series are constrained to have zero forecast covariance. We shall also introduce a possible method to relax this restriction. Copyright © 2008 John Wiley & Sons, Ltd. [source] Temporal aggregation and spurious instantaneous causality in multiple time series modelsJOURNAL OF TIME SERIES ANALYSIS, Issue 6 2002JÖRG BREITUNG Large aggregation interval asymptotics are used to investigate the relation between Granger causality in disaggregated vector autoregressions (VARs) and associated contemporaneous correlation among innovations of the aggregated system. One of our main contributions is that we outline various conditions under which the informational content of error covariance matrices yields insight into the causal structure of the VAR. Monte Carlo results suggest that our asymptotic findings are applicable even when the aggregation interval is small, as long as the time series are not characterized by high levels of persistence. [source] Bronchopulmonary dysplasia and brain white matter damage in the preterm infant: a complex relationshipPAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 6 2009Luigi Gagliardi Summary We analysed the relationship between bronchopulmonary dysplasia (BPD) and brain white matter damage (WMD) in very preterm infants, adjusting for common risk factors and confounders. We studied a cohort of infants <32 weeks gestational age (GA) and <1500 g, admitted to 12 hospitals in Northern Italy in 1999,2002. The association between BPD and WMD was estimated by generalised estimating equations and conditional logistic models, adjusting for centre, GA, propensity score for prolonged ventilation and other potential confounders. Directed acyclic graphs (DAG) were used to depict the underlying causal structure and guide analysis. Of the 1209 infants reaching 36 weeks, 192 (15.8%) developed BPD (supplemental oxygen at 36 weeks) and 88 (7.3%) ultrasound-defined WMD (cystic periventricular leukomalacia). In crude analysis, BPD was a strong risk factor for WMD [odds ratio (OR) = 5.9]. With successive adjustments, the OR progressively decreased to 3.88 when adjusting for GA, to 2.72 adding perinatal risk factors, and further down to 2.16 [95% confidence interval 1.1, 3.9] when ventilation was also adjusted for. Postnatal factors did not change the OR. Significant risk factors for WMD, in addition to BPD, were a low GA, a lower Apgar score, a higher illness severity score, ventilation and early-onset sepsis, while antenatal steroids, being small for GA, and surfactant were associated with a reduced risk. In conclusion, our data suggest that BPD is associated with an increased risk of WMD; most of the effect is due to shared risk factors and causal pathways. DAGs helped clarify the complex confounding of this scenario. [source] Introduction to the Epistemology of CausationPHILOSOPHY COMPASS (ELECTRONIC), Issue 6 2009Frederick Eberhardt This survey presents some of the main principles involved in discovering causal relations. They belong to a large array of possible assumptions and conditions about causal relations, whose various combinations limit the possibilities of acquiring causal knowledge in different ways. How much and in what detail the causal structure can be discovered from what kinds of data depends on the particular set of assumptions one is able to make. The assumptions considered here provide a starting point to explore further the foundations of causal discovery procedures, and how they can be improved. [source] Three Concepts of CausationPHILOSOPHY COMPASS (ELECTRONIC), Issue 3 2007Christopher Hitchcock I distinguish three different concepts of causation: The scientific concept, or causal structure, is the subject of recent work in causal modeling. The folk attributive concept has been studied by philosophers of law and social psychologists. The metaphysical concept is the one that metaphysicians have attempted to analyze. I explore the relationships between these three concepts, and suggest that the metaphysical concept is an untenable and dispensable mixture of the other two. [source] ELICITING A DIRECTED ACYCLIC GRAPH FOR A MULTIVARIATE TIME SERIES OF VEHICLE COUNTS IN A TRAFFIC NETWORKAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 3 2007Catriona M. Queen Summary The problem of modelling multivariate time series of vehicle counts in traffic networks is considered. It is proposed to use a model called the linear multiregression dynamic model (LMDM). The LMDM is a multivariate Bayesian dynamic model which uses any conditional independence and causal structure across the time series to break down the complex multivariate model into simpler univariate dynamic linear models. The conditional independence and causal structure in the time series can be represented by a directed acyclic graph (DAG). The DAG not only gives a useful pictorial representation of the multivariate structure, but it is also used to build the LMDM. Therefore, eliciting a DAG which gives a realistic representation of the series is a crucial part of the modelling process. A DAG is elicited for the multivariate time series of hourly vehicle counts at the junction of three major roads in the UK. A flow diagram is introduced to give a pictorial representation of the possible vehicle routes through the network. It is shown how this flow diagram, together with a map of the network, can suggest a DAG for the time series suitable for use with an LMDM. [source] Perceptual Causality in ChildrenCHILD DEVELOPMENT, Issue 6 2002Anne Schlottmann Three experiments considered the development of perceptual causality in children from 3 to 9 years of age (N= 176 in total). Adults tend to see cause and effect even in schematic, two,dimensional motion events: Thus, if square A moves toward B, which moves upon contact, they report that A launches B,physical causality. If B moves before contact, adults report that B tries to escape from A,social or psychological causality. A brief pause between movements eliminates such impressions. Even infants in the first year of life are sensitive to causal structure in both contact and no,contact events, but previous research with talking,age children found poor verbal reports. The present experiments used a picture,based forced,choice task to reduce linguistic demands. Observers saw eight different animations involving squares A and B. Events varied in whether or not these agents made contact; whether or not there was a delay at the closest point; and whether they moved rigidly or with a rhythmic, nonrigid "caterpillar" motion. Participants of all ages assigned events with contact to the physical domain and events without contact to the psychological domain. In addition, participants of all ages chose causality more often for events without delay than with delay, but these events became more distinct over the preschool range. The manipulation of agent motion had only minor and inconsistent effects across studies, even though children of all ages considered only the nonrigid motion to be animal,like. These results agree with the view that perceptual causality is available early in development. [source] A Causal Model Theory of the Meaning of Cause, Enable, and PreventCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 1 2009Steven Sloman Abstract The verbs cause, enable, and prevent express beliefs about the way the world works. We offer a theory of their meaning in terms of the structure of those beliefs expressed using qualitative properties of causal models, a graphical framework for representing causal structure. We propose that these verbs refer to a causal model relevant to a discourse and that "A causes B" expresses the belief that the causal model includes a link from A to B. "A enables/allows B" entails that the model includes a link from A to B, that A represents a category of events necessary for B, and that an alternative cause of B exists. "A prevents B" entails that the model includes a link from A to B and that A reduces the likelihood of B. This theory is able to account for the results of four experiments as well as a variety of existing data on human reasoning. [source] Past-president's address: is geography (the discipline) sustainable without geography (the subject)?THE CANADIAN GEOGRAPHER/LE GEOGRAPHE CANADIEN, Issue 2 2009CHRIS SHARPE géographie universitaire; géographie populaire; noyau disciplinaire; géographie régionale; disciplinocide We commonly define geography as the ,integrative' discipline, but there is more rhetoric than reality in the notion that our discipline has a coherent view of the world. Academic geography is dominated by increasingly esoteric topical specialties, and too often practiced as if it didn't exist outside the universities. By ignoring the popular conception of what geography is, we foster a dangerous opposition between geography as a popular subject and geography as a discipline. I argue that the survival of the discipline requires a collective rediscovery of a common core, which could be built around ,regional' geography,not the outmoded capes, bays and main export regional geography of the past, but one informed by modern theory, and attending to causal structures rooted in current realities. Our introductory courses are the best place to demonstrate a renewed commitment to a holistic geography grounded in an understanding of the world. Eclectic, curiosity-driven research is also essential to the survival of the discipline, but disciplinary diversity is a strength only if it is grounded in an identifiable core. Excessive pluralism and intellectual arrogance may lead to ,disciplinocide'. Les discours du président sortant: la géographie (la discipline) est-elle viable à long terme sans la géographie (le sujet)? Il faut reconnaître en effet que la géographie est une discipline , intégrative ,, mais l'idée que notre discipline porte un regard cohérent sur le monde tient plus de la rhétorique que de la réalité. La géographie universitaire aborde de plus en plus des domaines d'études ésotériques et la profession s'exerce généralement à l'écart du monde non universitaire en faisant fi de la conception populaire de la géographie. Le danger est que nous contribuions à mettre en opposition le sujet populaire et la discipline de la géographie. Il est soutenu que la pérennité de la discipline passe par une redécouverte collégiale d'une base commune qui pourrait se fonder sur la géographie , régionale ,.Celle-ci ne se pencherait pas sur les sujets dépassés tels que les caps, les baies ou les exportations principales, mais plutôt sur la théorie moderne en s'attelant aux structures de causalité qui correspondent aux réalités contemporaines. Les cours de base que nous proposons sont l'endroit par excellence pour manifester notre engagement renouvelé envers une géographie holistique fondée sur une compréhension du monde. Des travaux de recherche éclectiques et dictés par la curiosité sont garants de la pérennité de la discipline, mais la diversité de celle-ci constitue un atout seulement si elle est fondée sur un noyau bien établi. Un pluralisme abusif et une prétention intellectuelle pourraient conduire à un , disciplinocide ,. [source] | ||||||||||||||||