53,343 research outputs found
Modelling individual preferences, State of the art, recent advances and future directions.
No full textDespite the above famous statement, individuals have always disputed about individual tastes, and the decision making processes behind consumers’ choices has been a focal interest for decades. Although challenges against the theory of rational behaviour date back to the work of von Neumann and Morgenstern (1944), the dominating approach (at least in the transport field) has been the neoclassical economics assumption of rational decision makers (or even more extreme homo economicus), who always perform well planned and consistent activities, aiming to maximize some subjective measure of value (McFadden, 1999). The reason for this dominance is that economic theory has provided an elegant, rigorous and at the same time relatively easy to implement model, designed to describe individuals’ decisions and to provide quantitative forecasts with well-defined statistical properties. On the other hand, although investigations in psychology have made an impression on economic thought1 , they have tended to generate lists of errors and biases and have mostly failed (with excellent exceptions) to offer a coherent alternative to the rational-agent model (Kahneman, 2003). Psychologists recognise that this complaint is justified, at least partly, because intuitive thought cannot match the elegance and power of formal normative models. However, as Kahneman (2003) points out … “the alternative to simple and precise models is not chaos; psychology offers integrative concepts and mid-level generalizations, which gain credibility from their ability to explain ostensibly different phenomena in diverse domains”. The origin of this divergence relies on the historically different views of the decision-making process between neoclassical economics and psychology. While economists have been interested in mapping from information inputs to choice, treating the decision process as a black box, psychologists’ prime objective has been to understand what happens inside that black box: the nature of these decision elements, how they are established and modified by experience, and how they determine values. McFadden (1999) notes that what has made the distance between the two approaches even bigger is that psychologists view the decision process as dynamic and individual behaviour as local, adaptive, learned, dependent on context, mutable and influenced by complex interactions of perceptions, motives and attitudes. On the other hand, in the economic tradition preferences are primitive, consistent, and immutable (preference rationality), consumers behave as if they possess the formal tools with which to calculate the optimum adequately (perception-rationality), and the cognitive process is simply preference maximization, given market constraints (process-rationality). The models that we (transport researchers) currently use to describe how people choose among a discrete set of alternatives are based on these assumptions of rationality in preference, perception and process. McFadden’s work (1978; 1981) on Generalised Extreme Value (GEV) formulation, which generalised the work of Williams (1977), provides a rigorous foundation for consumer choice modelling derived from economic theory. Although the original formulation of the random utility maximisation (RUM) as a behavioural model followed the economists’ theory of consumer behaviour, it also included “features of the taste template that were heterogeneous across individuals and unknown to the analyst, as well as unobserved aspects of experience and of information on the attributes of alternatives, interpreted as random factors” (McFadden, 2000). This led to the paradigm for generating discrete-choice models (DCM), commonly reported in textbooks (Ben-Akiva and Lerman, 1985; Ortúzar and Willumsen, 2011; Train, 2009), that the random part of the individual utility reflects the modellers’ lack of complete information about all the elements considered by the individual making a choice, which might also include unobserved deviations of individual behaviour from perfect rationality. This paradigm posed the bases for the most important stream of research of the last 30 years. Since McFadden’s work, in fact, research activity in this field has been very proactive. Major progress has been made in exploring the potentiality of DCM to improve the ability to effectively reproduce individual behaviour. In particular, this paper draws attention to two streams of research motivated by this work. The first refers to the microeconomic justification of DCM and, in particular, of the utility individuals associate to each discrete alternative. The second stream, and maybe the most productive one, has been concerned with the characterization of the error terms, and in particular the exploitation of the mixed multinomial logit (MMNL) model. Research in both streams has aimed to improve the representation of the true phenomenon. However, the goal has always been that the measurable part of utility should be able to explain (as much as possible) the true behaviour in order to reduce the explanatory power left in the error term. This is correct except that, under the neo-classical theory, the systematic measurable utility was associated only with “rational” behaviour and what deviated from it was classified as error and hence minimised. Unfortunately, major improvements in model fit obtained with complex decompositions of the error term have given a strong signal that there are inherent limitations in the capability of microeconomic theory to explain individual choices and that we are still far from having a satisfactory representation (through known variables) of the real phenomenon. In fact, although RUM “takes a nod towards psychological theory” (Batley and Daly, 2006), the error term cannot be considered to properly explain behaviour that departs from perfect rationality. This is because errors are parameterized in terms of statistical distributions and the psychological concept of irrationality (i.e., not rational in the sense of neoclassical economic theory) is associated to the concept of randomness. As suggested by Ariely (2008), apparent irrationality can indeed be explained and predicted. Illustrious scholars (McFadden, 2000; Ben-Akiva, et al, 2002a) have strongly asserted the need to explore more seriously the suggestions provided by the psychological literature. After a shy start, the last decade has seen a surprising increase in the amount of work in this area (see for example Walker, 2001; Gärling and Axhausen, 2003; Bonsall, et al, 2007). Most of it has concentrated on demonstrating empirically that integrating psychology theory into the economic framework results in tangible improvement in terms of model fit, and interestingly most of it has been based on the MMNL structure. This is a key point, because the last years have also witnessed an increased awareness of the inherent limitations of the MMNL in terms of both estimation and especially prediction. In fact, notwithstanding the clear ability of this model to represent an ample range of behaviours via error term decomposition, several problems implicit in its structure have led analysts to lose confidence in the model. It is interesting then to understand whether or not these new models, which go beyond the rational postulate, still suffer from the above limitations or to what extent these are overcome. This paper presents a critical review of the research developments in the representation of the decision process, and it is structured into two parts. The first is dedicated to reviewing the limitations of the DCM and, in particular, of the MMNL model. Limits due to both the microeconomic theory of the rational user and the exploitation of the error terms will be critically discussed. The second part of the paper reviews research belonging to the non-rational theory. I concentrate on those advances that still rely heavily on the DCM with the aim to discuss to what extent we are really moving forward with respect to the above limitations of the classical MMNL model. Although focusing on research produced in the transport field, the paper provides and relies on several references from the literature in psychology and behavioural economics. Placing an accent on the limitations of current theory is not dictated by a pessimist view. On the contrary, it is intended as a proactive approach; these limitations constitute the starting point for and, above all, should stimulate new research. Another important consideration is that excellent reviews of both microeconomic theory (see McFadden, 2000; Bates, 2007; Jara-Díaz, 2007) and discrete choice models (see Ben-Akiva, et al, 2002b; Ortúzar, 2006; Bhat, 2007) already exist, while a review of their limitations seems yet to be undertaken; at least this is what emerges from research conducted over the last few years. The paper concludes by discussing some open questions raised by the research conducted so far and giving some final thoughts about the amazing challenge unfolding before us over the next years.<br/
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
New Parameters for Star Cluster Dynamics: The Role of Clusters Initial Conditions
No full textWe recently introduced three new parameters that describe the shape of the normalized cumulative radial distribution (nCRD) of the innermost stars in globular clusters (GCs) and trace the clusters’ dynamical evolution. Here, we extend our previous investigations to the case of a large set of Monte Carlo simulations of GCs, started from a broad range of initial conditions. All the models are analyzed at the same age of 13 Gyr when they have reached different evolutionary phases. The sample of models is well representative of the structural properties of the observed population of Galactic GCs. We confirm that the three nCRD parameters are powerful tools to distinguish systems in the early stages of dynamical evolution from those that have already experienced core collapse. They might also help disentangle clusters hosting a low-mass intermediate-mass black hole of a few hundred solar masses from cases with large concentrations of dark remnants in their centers. With respect to other dynamical indicators, the nCRD parameters offer the advantage of being fully empirical and easier to measure from observational data
Nuclis temàtics per a una geografia crítica: les propostes de D.R. Stoddart i D. Harvey
No full textL�autor introdueix el concepte de geografia crítica i comenta dues reflexions sobre la geografia.
Les aportacions de D. R. Stoddart a Berkeley el 1986 i D. Harvey a Heidelberg el 2004. Llurs
propostes propugnen una geografia crítica compromesa amb el coneixement i amb la solució dels
problemes ambientals i socials del seu temps.The author introduces the concept of critical geography and discusses two reflections on geography.
The contributions of D. R. Stoddart at Berkeley in 1986 and D. Harvey at Heidelberg in
2004. Their proposals advocate a critical geography committed with the knowledge and the solution
of environmental and social problems of his time
Cross-Clustered Model of Home-Based Work Participation Frequency During Traditionally Off-Work Hours
No full textR-4.2.0 with all libraries necessary for caMeL
No full textThis is a zipped file with R 4.2.0 and all libraries that are necessary for for caMeL interface operation. Simply follow the guidelines to prepare your environment.Disclaimer: this is a full environment for the software operations. I am not an author of it. You should cite the developers accordingly (https://ropensci.org/blog/2021/11/16/how-to-cite-r-and-r-packages/).</p
Gloeosporium cryptum Petch, Ann. R.
No full text<i>G. cryptum</i> Petch, Ann. R. bot. Gdns Peradeniya 7(4): 315 (1922) / IF 219637 <p>Typification Details: Holotype PDA 5255</p> <p>Reference: Petch (1922)</p>Published as part of <i>Wijayawardene, Nalin N., Dai, Dong-Qin, Premarathne, Bhagya M., Wimalasena, Madhara K., Jayalal, Udeni, Wickramanayake, Kawmini D., Dangalla, Hasanka, Jayathunga, Hashini, Brahmanage, Rashika S., Karunarathna, Samantha C., Weerakoon, Gothamie, Ariyawansa, Kahandawa G. S. U., Yapa, Neelamanie, Madawala, Sumedha, Nanayakkara, Chandrika M., Fan, Xin-Lei, Kirk, Paul M., Zhang, Gui-Qing, Ediriweera, Aseni, Bhat, Jayarama, Dawoud, Turki M. & Tibpromma, Saowaluck, 2023, Checklist, typification details, and nomenclature status of ascomycetous fungi originally described in Sri Lanka, pp. 1-105 in Phytotaxa 611 (1)</i> on page 45, DOI: 10.11646/phytotaxa.611.1.1, <a href="http://zenodo.org/record/8308739">http://zenodo.org/record/8308739</a>
Gloeosporium impatientis Petch, Ann. R.
No full text<i>G. impatientis</i> Petch, Ann. R. bot. Gdns Peradeniya 7(4): 315 (1922) / IF 183889 <p>Typification Details: Holotype PDA 6121</p> <p>Reference: Petch (1922)</p>Published as part of <i>Wijayawardene, Nalin N., Dai, Dong-Qin, Premarathne, Bhagya M., Wimalasena, Madhara K., Jayalal, Udeni, Wickramanayake, Kawmini D., Dangalla, Hasanka, Jayathunga, Hashini, Brahmanage, Rashika S., Karunarathna, Samantha C., Weerakoon, Gothamie, Ariyawansa, Kahandawa G. S. U., Yapa, Neelamanie, Madawala, Sumedha, Nanayakkara, Chandrika M., Fan, Xin-Lei, Kirk, Paul M., Zhang, Gui-Qing, Ediriweera, Aseni, Bhat, Jayarama, Dawoud, Turki M. & Tibpromma, Saowaluck, 2023, Checklist, typification details, and nomenclature status of ascomycetous fungi originally described in Sri Lanka, pp. 1-105 in Phytotaxa 611 (1)</i> on page 45, DOI: 10.11646/phytotaxa.611.1.1, <a href="http://zenodo.org/record/8308739">http://zenodo.org/record/8308739</a>
Symplocos hormiscioides Petch Ann. R.
No full text<i>S. hormiscioides</i> Petch Ann. R. bot. Gdns Peradeniya 7(4): 318 (1922) / IF 172724 <p>Typification Details: Holotype PDA 5343, On dead stems</p> <p>Reference: Petch (1922)</p>Published as part of <i>Wijayawardene, Nalin N., Dai, Dong-Qin, Premarathne, Bhagya M., Wimalasena, Madhara K., Jayalal, Udeni, Wickramanayake, Kawmini D., Dangalla, Hasanka, Jayathunga, Hashini, Brahmanage, Rashika S., Karunarathna, Samantha C., Weerakoon, Gothamie, Ariyawansa, Kahandawa G. S. U., Yapa, Neelamanie, Madawala, Sumedha, Nanayakkara, Chandrika M., Fan, Xin-Lei, Kirk, Paul M., Zhang, Gui-Qing, Ediriweera, Aseni, Bhat, Jayarama, Dawoud, Turki M. & Tibpromma, Saowaluck, 2023, Checklist, typification details, and nomenclature status of ascomycetous fungi originally described in Sri Lanka, pp. 1-105 in Phytotaxa 611 (1)</i> on page 27, DOI: 10.11646/phytotaxa.611.1.1, <a href="http://zenodo.org/record/8308739">http://zenodo.org/record/8308739</a>
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