The Complex Dynamics of Wishful Thinking The Critical Positivity Ratio

We examine critically the claims made by Fredrickson and Losada (2005) concerning the construct known as the “positivity ratio.” We find no theoretical or empirical justification for the use of differential equations drawn from fluid dynamics, a subfield of physics, to describe changes in human emotions over time; furthermore, we demonstrate that the purported application of these equations contains numerous fundamental conceptual and mathematical errors. The lack of relevance of these equations and their incorrect application lead us to conclude that Fredrickson and Losada’s claim to have demonstrated the existence of a critical minimum positivity ratio of 2.9013 is entirely unfounded. More generally, we urge future researchers to exercise caution in the use of advanced mathematical tools, such as nonlinear dynamics, and in particular to verify that the elementary conditions for their valid application have been met

Positive Psychology and Romantic Scientism

Replies to the comments of Nickerson (see record 2014-36500-010), Guastello (see record 2014-36500-011), Musau (see record 2014-36500-013), Hämäläinen et al. (see record 2014-36500-014), and Lefebvre and Schwartz (see record 2014-36500-015) on the authors article (see record 2013-24609-001). Fredrickson and Losada’s (2005) article was the subject of over 350 scholarly citations before our critique (Brown et al., 2013) appeared, and its principal “conclusions” have been featured in many lectures and public presentations by senior members of the positive psychology research community, although its deficiencies ought to have been visible to anyone with a modest grasp of mathematics and a little curiosity. Unfortunately— because human behavior is, after all, complex and difficult to understand—we have no way of knowing whether the fact that it took so long for these deficiencies to be recognized was due to an unwarranted degree of optimism about the reliability of the peer-review process, a reluctance to make waves in the face of powerful interests, a general lack of critical thinking within positive psychology, or some other factor. We hope that our revelation of the problems with the critical positivity ratio ultimately demonstrates the success of science as a self-correcting endeavor; however, we would have greatly preferred it if our work had not been necessary in the first place. (PsycINFO Database Record (c) 2016 APA, all rights reserved

The Persistence of Wishful Thinking

Comments on the article by Fredrickson and Losada (see record 2005-11834-001). Recently the current authors (Brown, Sokal, & Friedman, 2013) debunked the widely cited claim made by Fredrickson and Losada (2005) that their use of a mathematical model drawn from nonlinear dynamics (namely, the Lorenz equations from fluid dynamics) provided theoretical support for the existence of a pair of critical positivity-ratio values (2.9013 and 11.6346) such that individuals whose ratios fall between these values will “flourish,” whereas people whose ratios lie outside this ideal range will “languish.” For lack of space in our previous article, we refrained from addressing, except in passing, the question of whether there might be empirical evidence for the existence of one or more critical positivity ratios (“tipping points”). In response to our critique, Fredrickson and Losada (2013) withdrew their nonlinear dynamics model, but Fredrickson (December December 2013) reaffirmed some claims concerning positivity ratios on the basis of empirical studies. We would therefore like to comment briefly on these claims and the alleged supporting evidence. (PsycINFO Database Record (c) 2016 APA, all rights reserved

Microcanonical studies on isoscaling

The exponential scaling of isotopic yields is investigated for sources of different sizes over a broad range of excitation energies and freeze-out volumes, in both primary and asymptotic stages of the decay in the framework of a microcanonical multifragmentation model. It was found that the scaling parameters have a strong dependence on the considered pair of equilibrated sources and excitation energy and are affected by the secondary particle emission of the break-up fragments. No significant influence of the freeze-out volume on the considered isotopic ratios has been observed. Deviations of microcanonical results from grandcanonical expectations are discussed.Comment: 19 pages, 6 figure

Irradiation of Materials with Short, Intense Ion pulses at NDCX-II

We present an overview of the performance of the Neutralized Drift Compression Experiment-II (NDCX-II) accelerator at Berkeley Lab, and report on recent target experiments on beam driven melting and transmission ion energy loss measurements with nanosecond and millimeter-scale ion beam pulses and thin tin foils. Bunches with around 10^11 ions, 1-mm radius, and 2-30 ns FWHM duration have been created with corresponding fluences in the range of 0.1 to 0.7 J/cm^2. To achieve these short pulse durations and mm-scale focal spot radii, the 1.1 MeV He+ ion beam is neutralized in a drift compression section, which removes the space charge defocusing effect during final compression and focusing. The beam space charge and drift compression techniques resemble necessary beam conditions and manipulations in heavy ion inertial fusion accelerators. Quantitative comparison of detailed particle-in-cell simulations with the experiment play an important role in optimizing accelerator performance.Comment: 15 pages, 7 figures. revised manuscript submitted to Laser and Particle Beam

Break-up stage restoration in multifragmentation reactions

In the case of Xe+Sn at 32 MeV/nucleon multifragmentation reaction break-up fragments are built-up from the experimentally detected ones using evaluations of light particle evaporation multiplicities which thus settle fragment internal excitation. Freeze-out characteristics are extracted from experimental kinetic energy spectra under the assumption of full decoupling between fragment formation and energy dissipated in different degrees of freedom. Thermal kinetic energy is determined uniquely while for freeze-out volume - collective energy a multiple solution is obtained. Coherence between the solutions of the break-up restoration algorithm and the predictions of a multifragmentation model with identical definition of primary fragments is regarded as a way to select the true value. The broad kinetic energy spectrum of $^3$He is consistent with break-up genesis of this isotope.Comment: 17 pages, 5 figure

Memory for medication side effects in younger and older adults: the role of subjective and objective importance

Older adults often experience memory impairments, but can sometimes use selective processing and schematic support to remember important information. The current experiments investigate to what degree younger and healthy older adults remember medication side effects that were subjectively or objectively important to remember. Participants studied a list of common side effects, and rated how negative these effects were if they were to experience them, and were then given a free recall test. In Experiment 1, the severity of the side effects ranged from mild (e.g., itching) to severe (e.g., stroke), and in Experiment 2, certain side effects were indicated as critical to remember (i.e., “contact your doctor if you experience this”). There were no age differences in terms of free recall of the side effects, and older adults remembered more severe side effects relative to mild effects. However, older adults were less likely to recognize critical side effects on a later recognition test, relative to younger adults. The findings suggest that older adults can selectively remember medication side effects, but have difficulty identifying familiar but potentially critical side effects, and this has implications for monitoring medication use in older age

Sequestration of Martian CO2 by mineral carbonation

Carbonation is the water-mediated replacement of silicate minerals, such as olivine, by carbonate, and is commonplace in the Earth’s crust. This reaction can remove significant quantities of CO2 from the atmosphere and store it over geological timescales. Here we present the first direct evidence for CO2 sequestration and storage on Mars by mineral carbonation. Electron beam imaging and analysis show that olivine and a plagioclase feldspar-rich mesostasis in the Lafayette meteorite have been replaced by carbonate. The susceptibility of olivine to replacement was enhanced by the presence of smectite veins along which CO2-rich fluids gained access to grain interiors. Lafayette was partially carbonated during the Amazonian, when liquid water was available intermittently and atmospheric CO2 concentrations were close to their present-day values. Earlier in Mars’ history, when the planet had a much thicker atmosphere and an active hydrosphere, carbonation is likely to have been an effective mechanism for sequestration of CO2

Propagation of chaos for rank-based interacting diffusions and long time behaviour of a scalar quasilinear parabolic equation

We study a quasilinear parabolic Cauchy problem with a cumulative distribution function on the real line as an initial condition. We call 'probabilistic solution' a weak solution which remains a cumulative distribution function at all times. We prove the uniqueness of such a solution and we deduce the existence from a propagation of chaos result on a system of scalar diffusion processes, the interactions of which only depend on their ranking. We then investigate the long time behaviour of the solution. Using a probabilistic argument and under weak assumptions, we show that the flow of the Wasserstein distance between two solutions is contractive. Under more stringent conditions ensuring the regularity of the probabilistic solutions, we finally derive an explicit formula for the time derivative of the flow and we deduce the convergence of solutions to equilibrium.Comment: Stochastic partial differential equations: analysis and computations (2013) http://dx.doi.org/10.1007/s40072-013-0014-