When and how to use scenario planning: A heuristic approach with illustration

This paper offers a step-by-step analysis of a heuristic approach to scenario planning, taking a managerial perspective. The scenario method is contrasted in general with more traditional planning techniques, which tend to perform less well when faced with high uncertainty and complexity. An actual case involving a manufacturing company is used to illustrate the main steps of the proposed heuristic. Its essence is to identify relevant trends and uncertainties, and blend them into scenarios that are internally consistent. In addition, the scenarios should bound the range of plausible uncertainties and challenge managerial thinking. Links to decision making are examined next, including administrative policies as well as integrative techniques. At the strategic level, a key-success-factor matrix is proposed for integrating scenarios, competitor analysis and strategic vision. At the operational level, Monte Carlo simulation is suggested and illustrated as one useful technique for combining scenario thinking with formal project evaluation (after appropriate translations). The paper concludes with a general discussion of scenario planning, to place it in a broader perspective.     

Robert Boyle and the heuristic value of mechanism

This paper argues that, contrary to the claims of Alan Chalmers, Boyle understood his experimental work to be intimately related to his mechanical philosophy. Its central claim is that the mechanical philosophy has a heuristic structure that motivates and gives direction to Boyle's experimental programme. Boyle was able to delimit the scope of possible explanations of any phenomenon by positing both that all qualities are ultimately reducible to a select group of mechanical qualities and that all explanations of natural phenomena are to be in terms of the operations of machines and are to appeal only to qualities that are already familiar. This is illustrated by his investigations into the Torricellian experiment. Boyle's explanation of the elevation of the mercurial cylinder by appeal to the spring of the air was an intermediate mechanical explanation. Boyle was convinced that the spring of the air was ultimately reducible to the mechanical qualities. This in turn had implications for his research into the cause of respiration. In a move that was both parsimonious and consistent with the broad requirements of the mechanical philosophy, Boyle was able to solve the problem of the cause of the inflow of air into the lungs by appeal to his research in pneumatics. This application of a mechanical explanation in pneumatics to physiology is just what one would expect if the mechanical philosophy was as universal as Boyle claimed it to be. Therefore, far from Boyle's experiments having a life of their own, they were clearly directed by and understood in terms of the mechanical philosophy.     

Existential risk,creativity & well-adapted science

Existential risks, particularly those arising from emerging technologies, are a complex, obstinate challenge for scientific study. This should motivate studying how the relevant scientific communities might be made more amenable to studying such risks. I offer an account of scientific creativity suitable for thinking about scientific communities, and provide reasons for thinking contemporary science doesn't incentivise creativity in this specified sense. I'll argue that a successful science of existential risk will be creative in my sense. So, if we want to make progress on those questions we should consider how to shift scientific incentives to encourage creativity. The analysis also has lessons for philosophical approaches to understanding the social structure of science. I introduce the notion of a ‘well-adapted’ science: one in which the incentive structure is tailored to the epistemic situation at hand.     

The anchor and adjustment heuristic in time-series forecasting

This paper explores the relevance of the anchor and adjustment heuristic in judgmental time-series extrapolation. Using a database of real time series it examines the proposition that people anchor on the last history value of the series and make insufficient adjustments from it in making their forecast. In contrast to studies in behavioral decision making, analysis shows that the anchor and adjustment heuristic does not describe the behavior of time-series forecasters. Adjustments from the anchor are often excessive, not insufficient. A number of possible explanations for this exceptional finding are explored.     

The role of heuristic appraisal in conflicting assessments of string theory

Over the last three decades, string theory has emerged as one of the leading hopes for a consistent theory of quantum gravity that unifies particle physics with general relativity. Despite the fact that string theory has been a thriving research program for the better part of three decades, it has been subjected to extensive criticism from a number of prominent physicists. The aim of this paper is to obtain a clearer picture of where the conflict lies in competing assessments of string theory, through a close reading of the argumentative strategies employed by protagonists on both sides. Although it has become commonplace to construe this debate as stemming from different attitudes to the absence of testable predictions, we argue that this presents an overly simplified view of the controversy, which ignores the critical role of heuristic appraisal. While string theorists and their defenders see the theoretical achievements of the string theory program as providing strong indication that it is ‘on the right track’, critics have challenged such claims, by calling into question the status of certain ‘solved problems’ and its purported ‘explanatory coherence’. The debates over string theory are therefore particularly instructive from a philosophical point of view, not only because they offer important insights into the nature of heuristic appraisal and theoretical progress, but also because they raise deep questions about what constitutes a solved problem and an explanation in fundamental physics.     

The heuristic role of mathematics in the initial development of superconductivity theory

During the first twenty-four years after the discovery of superconductivity many attempts to derive an adequate theory failed, mainly because the problem was not formulated quite correctly. In this paper we investigate certain questions related to the heuristic role of mathematics in the appropriate formulation of the problem that had to be solved and the development of a theory which was hindered by theoretical superstitions.     

A rat model of neurobehavioral development

Summary The neurobehavioral evolution of the normally growing rat has been investigated by means of a series of reflex, motor and sensory tests from birth up to weaning. A sequential development of behavioral reponses has been assessed over this 21-days period, the 2nd week following birth representing an important step in the neurobehavioral maturation of the rat. This rat model may be considered as an useful reference to evaluate changes that may be induced by pharmacological and toxicological agents in the developing exposed rat.Acknowledgment. We thank Mrs D. Huot-Blais for her secretarial assistance.     

A model of enzymatic kinetics]

In this Note, we study a system of differential equations representing the kinetics of an enzymatic reaction. For a closed system, and in the domain where it has a biological significance, it is shown that: (i) there exists a unique equilibrium point, which is an asymptotically stable point; (ii) if several enzymes act on the same substrates, the equilibrium values of the substrates concentrations take their values within the range of the equilibrium values achieved with each of these enzymes, (iii) the kinetics of the reaction can be approached by a single first-order differential equation, which may be seen as a generalization of the Michaelis equation.     

The usefulness of heuristic N(E)RLS algorithms for combining forecasts

There exists theoretical and empirical evidence on the efficiency and robustness of Non-negativity Restricted Least Squares combinations of forecasts. However, the computational complexity of the method hinders its widespread use in practice. We examine various optimizing and heuristic computational algorithms for estimating NRLS combination models and provide certain CPU-time reducing implementations. We empirically compare the combination weights identified by the alternative algorithms and their computational demands based on a total of more than 66,000 models estimated to combine the forecasts of 37 firm-specific accounting earnings series. The ex ante prediction accuracies of combined forecasts from the optimizing versus heuristic algorithms are compared. The effects of fit sample size, model specification, multicollinearity, correlations of forecast errors, and series and forecast variances on the relative accuracy of the optimizing versus heuristic algorithms are analysed. The results reveal that, in general, the computationally simple heuristic algorithms perform as well as the optimizing algorithms. No generalizable conclusions could be reached, however, about which algorithm should be used based on series and forecast characteristics. © 1997 John Wiley & Sons, Ltd.     

A threshold stochastic volatility model

This article introduces a new model to capture simultaneously the mean and variance asymmetries in time series. Threshold non‐linearity is incorporated into the mean and variance specifications of a stochastic volatility model. Bayesian methods are adopted for parameter estimation. Forecasts of volatility and Value‐at‐Risk can also be obtained by sampling from suitable predictive distributions. Simulations demonstrate that the apparent variance asymmetry documented in the literature can be due to the neglect of mean asymmetry. Strong evidence of the mean and variance asymmetries was detected in US and Hong Kong data. Asymmetry in the variance persistence was also discovered in the Hong Kong stock market. Copyright © 2002 John Wiley & Sons, Ltd.     

A model for investigating erythropoiesis

Zusammenfassung Ein Modell zur Untersuchung der Erythropoese zeigt zwei Hauptmerkmale. Erstens aktiviert eine schnelle Veränderung der Sauerstoffsensoren unmittelbar das gespeicherte und das im Umlauf befindliche Erythropoetin. Zweitens wird der normale Verlauf des Umsatzes von roten Blutkörperchen durch die Sauerstoffsensoren beeinflusst, die die Hypothalamuskontrolle des zyklischen Verhaltens des Hypophysenzwischenlappens und seiner innerdrüslichen Kolloidproduktion steuern.

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this study was supported by a grant from the National Research Council of Canada.     

A non representationalist view of model explanation

In this paper, I examine two idealized models in astrophysics, with the aim of showing that the idealizations in these models play an important explanatory role. I argue, against many representationalists, that it is because of the idealizations in these models, rather than in spite of them, that the models turn out to have explanatory power. In many cases, this claim can be extended to the use of idealized models in the sciences more generally, and thus it gives important insight into the nature of model explanation.     

A new model of glucocorticoid-induced metanephric maldevelopment

Summary A new experimental model of glucocortocoid-induced tubular cyst formation has been developed in metanephric organ culture. The addition of cortisol (1.4×10^–5 M) to chemically defined serum-free culture medium produces cystic changes during in vitro nephrogenesis. The model isolates the role of glucocorticoids in experimental cyst formation.Acknowledgment. This work has been supported by Basil O'Connor Starter Research Grant No.5-349 from the March of Dimes Birth Defects Foundation.     

A model of nucleolar structure and behaviour

Zusammenfassung Ein mathematisches Modell wird beschrieben, wobei der Nukleolus als offenes System die fibrilläre RNS und die Ribonukleoproteingranula als Komplexstruktur aufgefasst werden. Die Formeln verwenden: Kerndurchmesser, Geschwindigkeit der Bildung von fibrillärer RNS, Moleküllänge, Halbwertszeit ihres Zerfalls sowie die Dichte der Ribonukleoproteingranula.     

A rat model of neurobehavioral development.

The neurobehavioral evolution of the normally growing rat has been investigated by means of a series of reflex, motor and sensory tests from birth up to weaning. A sequential development of behavioral responses has been assessed over this 21-days period, and 2nd week following birth representing an important step in the neurobehavioral maturation of the rat. This rat model may be considered as an useful reference to evaluate changes that may be induced by pharmacological and toxicological agents in the developing exposed rat.     

A new model of glucocorticoid-induced metanephric maldevelopment

A new experimental model of glucocorticoid-induced tubular cyst formation has been developed in metanephric organ culture. The addition of cortisol (1.4 X 10(-5) M) to chemically defined serum-free culture medium produces cystic changes during in vitro nephrogenesis . The model isolates the role of glucocorticoids in experimental cyst formation.