138 research outputs found
Individual differences and strategies for human reasoning
Theories of human reasoning have tended to assume cognitive universality, i. e. that all
individuals reason in basically the same way. However, some research (e. g. that of Ford.
1995) has found evidence of individual differences in the strategies people use for
syllogistic reasoning. This thesis presents a series of experiments which aimed to identify
individual differences in strategies for human reasoning and investigate their nature and
aetiology. Experiment 1 successfully replicated and extended Ford (1995) and provided
further evidence that most individuals prefer to reason with either verbal-propositional or
visuo-spatial representations. Data from verbal and written protocols showed that verbal
reasoners tended to use a method of substitution whereby they obtain a value for the
common term from one premise and then simply substitute it in the other premise to obtain
a conclusion. Spatial reasoners, on the other hand, presented protocols which resembled
Euler circles and described the syllogistic premises in terms of sets and subsets.
Experiment 2 provided some further qualitative evidence about the nature of such
strategies, especially the verbal reasoners, showing that within strategy variations occurred.
Experiment 3 extended this line of research, identifying a strong association between
verbal and spatial strategies for syllogistic reasoning and abstract and concrete strategies
for transitive inference (the latter having originally been identified by Egan and Grimes-
Farrow, 1982). Experiments 1-3 also showed that inter-strategic differences in accuracy are
generally not observed, hence, reasoners present an outward appearance of ubiquity despite
underlying differences in reasoning processes. Experiments 5 and 6 investigated individual
differences in cognitive factors which may underpin strategy preference. Whilst no
apparent effects of verbal and spatial ability or cognitive style were found, reasoners did
appear to draw differentially on the verbal and spatial components of working memory.
Confirmatory factor analysis showed that whilst verbal reasoners draw primarily on the
verbal memory resource, spatial reasoners draw both on this and on spatial resource.
Overall, these findings have important implications for theories of human reasoning, which
need to take into account possible individual differences in strategies if they are to present
a truly comprehensive account of how people reason.Economic and Social
Research Counci
Stellar Collisions and the Interior Structure of Blue Stragglers
Collisions of main sequence stars occur frequently in dense star clusters. In
open and globular clusters, these collisions produce merger remnants that may
be observed as blue stragglers. Detailed theoretical models of this process
require lengthy hydrodynamic computations in three dimensions. However, a less
computationally expensive approach, which we present here, is to approximate
the merger process (including shock heating, hydrodynamic mixing, mass
ejection, and angular momentum transfer) with simple algorithms based on
conservation laws and a basic qualitative understanding of the hydrodynamics.
These algorithms have been fine tuned through comparisons with the results of
our previous hydrodynamic simulations. We find that the thermodynamic and
chemical composition profiles of our simple models agree very well with those
from recent SPH (smoothed particle hydrodynamics) calculations of stellar
collisions, and the subsequent stellar evolution of our simple models also
matches closely that of the more accurate hydrodynamic models. Our algorithms
have been implemented in an easy to use software package, which we are making
publicly available (see http://vassun.vassar.edu/~lombardi/mmas/). This
software could be used in combination with realistic dynamical simulations of
star clusters that must take into account stellar collisions.Comment: This revised version has 37 pages, 13 figures, 4 tables; submitted to
ApJ; for associated software package, see
http://vassun.vassar.edu/~lombardi/mmas/ This revised version presents
additional comparisons with SPH results and slightly improved merger recipe
Finding Silver Linings in the Covid-19 Pandemic: A 2-Wave Study in the UK
The Covid-19 pandemic has resulted in widespread anxiety, fear and depression, yet focussing only on these negative issues may obscure the opportunity to promote positivity and resilience. Traumatic events can often result in positive life changes (adversarial growth) though there is little evidence in the context of pandemics, and no previous studies in Covid-19 with the general public. The present research investigated whether adversarial growth was perceived in Covid-19 and whether this could account for variance in wellbeing, over and above effects of personality traits. Participants recruited from the UK public ( N = 183) completed the Big Five Personality Inventory, the WHO-5 Wellbeing Scale and the Silver Lining Questionnaire (SLQ) measure of adversarial growth. Questionnaires were completed online, at two timepoints, nine months apart. At Time 1, wellbeing was negatively associated with trait Neuroticism and positively associated with Openness to experience. Both associations were positively mediated by SLQ score. At Time 2, SLQ score again mediated the effects of Openness on wellbeing, and also the influence of wellbeing at Time 1 on that at Time 2. Reported Silver Linings included strengthened personal relationships at Time 1, and improved ability to handle life events at Time 2. This suggests a shift from an appreciation of relationships to an awareness of personal development once life returned to some semblance of normality. Overall, results suggest that perceived adversarial growth supported wellbeing during the pandemic and highlight a focus for therapeutic intervention. </jats:p
The Distribution of Collisionally Induced Blue Stragglers in the Colour-Magnitude Diagram
A primary production mechanism for blue stragglers in globular clusters is
thought to be collisionally-induced mergers, perhaps mediated by dynamical
encounters involving binary stars. We model the formation and evolution of such
blue stragglers, and produce theoretical distributions of them in the
colour-magnitude diagram. We use a crude representation of cluster dynamics and
detailed binary-single star encounter simulations to produce cross sections and
rates for a variety of collisions. The results of the collisions are determined
based on SPH simulations of realistic star models. The evolution of the
collision products are then followed in detail.
We use our results to explore the effects of a variety of input assumptions
on the number and kind of blue stragglers created by collisions. In particular,
we describe the changes in the blue straggler distribution that result from
using realistic collision products rather than the ``fully-mixed'' assumption,
and from changes in assumptions about the number and orbital period
distribution of the primordial binary population. We then apply our models to
existing data from the core of M3, where the large blue straggler population is
thought to be dominated by collision products. We find that we have difficulty
successfully modeling the observed blue stragglers under a single consistent
set of assumptions. However, if 3 particularly bright blue stragglers are
considered to be part of a different observed population, the remainder can be
successfully modeled using realistic encounter products and assuming a 20%
binary fraction with plausible period distribution.Comment: 36 pages including 8 figures, submitted to Astrophysical Journa
An Analytic Model for Blue Straggler Formation in Globular Clusters
We present an analytic model for blue straggler formation in globular
clusters. We assume that blue stragglers are formed only through stellar
collisions and binary star evolution, and compare our predictions to observed
blue straggler numbers taken from the catalogue of Leigh, Sills & Knigge
(2011). We can summarize our key results as follows: (1) Binary star evolution
consistently dominates blue straggler production in all our best-fitting
models. (2) In order to account for the observed sub-linear dependence of blue
straggler numbers on the core masses (Knigge, Leigh & Sills 2009), the core
binary fraction must be inversely proportional to the total cluster luminosity
and should always exceed at least a few percent. (3) In at least some clusters,
blue straggler formation must be enhanced by dynamical encounters (either via
direct collisions or by stimulating mass-transfer to occur by altering the
distribution of binary orbital parameters) relative to what is expected by
assuming a simple population of binaries evolving in isolation. (4) The
agreement between the predictions of our model and the observations can be
improved by including blue stragglers that form outside the core but later
migrate in due to dynamical friction. (5) Longer blue straggler lifetimes are
preferred in models that include blue stragglers formed outside the core since
this increases the fraction that will have sufficient time to migrate in via
dynamical friction.Comment: 11 pages, 4 figures, accepted for publication in MNRA
Evolution of Stellar Collision Products in Globular Clusters - II. Off-axis Collision
We continue our exploration of collisionally merged stars in the blue
straggler region of the color-magnitude diagram. We report the results of new
SPH calculations of parabolic collisions between two main-sequence stars, with
the initial structure and composition profiles of the parent stars having been
determined from stellar evolution calculations. Parallelization of the SPH code
has permitted much higher numerical resolution of the hydrodynamics. We also
present evolutionary tracks for the resulting collision products, which emerge
as rapidly rotating blue stragglers. The rotating collision products are
brighter, bluer and remain on the main sequence longer than their non-rotating
counterparts. In addition, they retain their rapid rotation rates throughout
their main sequence lifetime. Rotationally-induced mixing strongly affects the
evolution of the collision products, although it is not sufficient to mix the
entire star. We discuss the implications of these results for studies of blue
straggler populations in clusters. This work shows that off-axis collision
products cannot become blue stragglers unless they lose a large fraction of
their initial angular momentum. The mechanism for this loss is not apparent,
although some possibilities are discussed.Comment: 25 pages incl. 9 figures (one in colour). Submitted to Ap
Mutational analysis of disease relapse in patients allografted for acute myeloid leukemia
Disease relapse is the major cause of treatment failure after allogeneic stem cell transplantation (allo-SCT) in acute myeloid leukemia (AML). To identify AML-associated genes prognostic of AML relapse post–allo-SCT, we resequenced 35 genes in 113 adults at diagnosis, 49 of whom relapsed. Two hundred sixty-two mutations were detected in 102/113 (90%) patients. An increased risk of relapse was observed in patients with mutations in WT1 (P = .018), DNMT3A (P = .045), FLT3 ITD (P = .071), and TP53 (P = .06), whereas mutations in IDH1 were associated with a reduced risk of disease relapse (P = .018). In 29 patients, we additionally compared mutational profiles in bone marrow at diagnosis and relapse to study changes in clonal structure at relapse. In 13/29 patients, mutational profiles altered at relapse. In 9 patients, mutations present at relapse were not detected at diagnosis. In 15 patients, additional available pre–allo-SCT samples demonstrated that mutations identified posttransplant but not at diagnosis were detectable immediately prior to transplant in 2 of 15 patients. Taken together, these observations, if confirmed in larger studies, have the potential to inform the design of novel strategies to reduce posttransplant relapse highlighting the potential importance of post–allo-SCT interventions with a broad antitumor specificity in contrast to targeted therapies based on mutational profile at diagnosis
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Motivating Emotional Intelligence: A Reinforcement Sensitivity Theory (RST) Perspective
Trait emotional intelligence (trait EI) is generally associated with positive outcomes and can inform clinical and social interventions. We investigated the sub-factors of trait EI: Wellbeing, Self-control, Emotionality, and Sociability, in the context of the Reinforcement Sensitivity Theory (RST) of motivation. In Study 1, participants (N = 247) completed Carver and White’s (1994) BIS/BAS scales and a measure of trait EI. All EI sub-factors were positively associated with BAS Drive and negatively with BIS. Study 2 (N = 382) employed a new questionnaire based on revised RST (Corr & Cooper, 2016). All trait EI factors were positively associated with BAS Goal-Drive Persistence and Reward Interest, and negatively with the BIS. Self-control showed negative associations with BAS Impulsivity and was the only factor not to correlate with BAS Reward Reactivity. Results suggest that high trait EI individuals are goal driven, sensitive to reward and lower in avoidance motivation and negative emotion. This motivational basis to trait EI further explicates its structure
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