3,792 research outputs found
Evolutionary game dynamics of controlled and automatic decision-making
We integrate dual-process theories of human cognition with evolutionary game
theory to study the evolution of automatic and controlled decision-making
processes. We introduce a model where agents who make decisions using either
automatic or controlled processing compete with each other for survival. Agents
using automatic processing act quickly and so are more likely to acquire
resources, but agents using controlled processing are better planners and so
make more effective use of the resources they have. Using the replicator
equation, we characterize the conditions under which automatic or controlled
agents dominate, when coexistence is possible, and when bistability occurs. We
then extend the replicator equation to consider feedback between the state of
the population and the environment. Under conditions where having a greater
proportion of controlled agents either enriches the environment or enhances the
competitive advantage of automatic agents, we find that limit cycles can occur,
leading to persistent oscillations in the population dynamics. Critically,
however, these limit cycles only emerge when feedback occurs on a sufficiently
long time scale. Our results shed light on the connection between evolution and
human cognition, and demonstrate necessary conditions for the rise and fall of
rationality.Comment: 9 pages, 7 figure
Social heuristics and social roles: Intuition favors altruism for women but not for men
Are humans intuitively altruistic, or does altruism require self-control? A theory of social heuristics, whereby intuitive responses favor typically successful behaviors, suggests that the answer may depend on who you are. In particular, evidence suggests that women are expected to behave altruistically, and are punished for failing to be altruistic, to a much greater extent than men. Thus, women (but not men) may internalize altruism as their intuitive response. Indeed, a meta-analysis of 13 new experiments and 9 experiments from other groups found that promoting intuition increased giving in a Dictator Game among women, but not among men (Study 1). Furthermore, this effect was shown to be moderated by explicit sex role identification (Study 2, N=1,831): the more women described themselves using traditionally masculine attributes (e.g., dominance, independence) relative to traditionally feminine attributes (e.g., warmth, tenderness), the more deliberation reduced their altruism. Our findings shed light on the connection between gender and altruism, and highlight the importance of social heuristics in human prosociality
Cluster approximations for infection dynamics on random networks
In this paper, we consider a simple stochastic epidemic model on large
regular random graphs and the stochastic process that corresponds to this
dynamics in the standard pair approximation. Using the fact that the nodes of a
pair are unlikely to share neighbors, we derive the master equation for this
process and obtain from the system size expansion the power spectrum of the
fluctuations in the quasi-stationary state. We show that whenever the pair
approximation deterministic equations give an accurate description of the
behavior of the system in the thermodynamic limit, the power spectrum of the
fluctuations measured in long simulations is well approximated by the
analytical power spectrum. If this assumption breaks down, then the cluster
approximation must be carried out beyond the level of pairs. We construct an
uncorrelated triplet approximation that captures the behavior of the system in
a region of parameter space where the pair approximation fails to give a good
quantitative or even qualitative agreement. For these parameter values, the
power spectrum of the fluctuations in finite systems can be computed
analytically from the master equation of the corresponding stochastic process.Comment: the notation has been changed; Ref. [26] and a new paragraph in
Section IV have been adde
Geometric scaling in high-energy QCD at nonzero momentum transfer
We show how one can obtain geometric scaling properties from the
Balitsky-Kovchegov (BK) equation. We start by explaining how, this property
arises for the b-independent BK equation. We show that it is possible to extend
this model to the full BK equation including momentum transfer. The saturation
scale behaves like max(q,Q_T) where q is the momentum transfer and Q_T a
typical scale of the target.Comment: 4 pages, 2 figures. Talk given by G. Soyez at the "Rencontres de
Moriond", 12-19 March 2005, La Thuile, Ital
âMy Future is Nowâ: A Qualitative Study of Persons Living With Advanced Cancer
Objectives:
Advance care planning (ACP) enables individuals to deliberate about future preferences for care based upon their values and beliefs about what is important in life. For many patients with advanced cancer, however, these critical conversations do not occur. A growing body of literature has examined the end-of-life wishes of seriously ill patients. Few studies have explored what is important to persons as they live with advanced cancer. The aim of the current study was to address this gap and to understand how clinicians can support patientsâ efforts to live in the present and plan for the future.
Methods:
Transcriptions of interviews conducted with 36 patients diagnosed with advanced cancer were analyzed using immersionâcrystallization, a qualitative research technique.
Results:
Four overarching themes were identified: (I) living in the face of death, (II) who I am, (III) my experience of cancer, and (IV) impact of my illness on others. Twelve subthemes are also reported.
Significance of Results:
These findings have significant implications for clinicians as they partner with patients to plan for the future. Our data suggest that clinicians consider the following 4 prompts: (1) âWhat is important to you now, knowing that you will die sooner than you want or expected?â (2) âTell me about yourself.â (3) âTell me in your own words about your experience with cancer care and treatment.â (4) âWhat impact has your illness had on others?â In honoring patientsâ lived experiences, we may establish the mutual understanding necessary to providing high-quality care that supports patientsâ priorities for life
A GBT Survey of the HALOGAS Galaxies and Their Environments I: Revealing the full extent of HI around NGC891, NGC925, NGC4414 & NGC4565
We present initial results from a deep neutral hydrogen (HI) survey of the
HALOGAS galaxy sample, which includes the spiral galaxies NGC891, NGC925,
NGC4414, and NGC4565, performed with the Robert C. Byrd Green Bank Telescope
(GBT). The resulting observations cover at least four deg around these
galaxies with an average 5 detection limit of 1.210
cm over a velocity range of 20 km s and angular scale of 9.1.
In addition to detecting the same total flux as the GBT data, the spatial
distribution of the GBT and original Westerbork Synthesis Radio Telescope
(WSRT) data match well at equal spatial resolutions. The HI mass fraction below
HI column densities of 10 cm is, on average, 2\%. We discuss the
possible origins of low column density HI of nearby spiral galaxies. The
absence of a considerable amount of newly detected HI by the GBT indicates
these galaxies do not have significant extended diffuse HI structures, and
suggests future surveys planned with the SKA and its precursors must go
\textit{at least} as deep as 10 cm in column density to
significantly increase the probability of detecting HI associated with the
cosmic web and/or cold mode accretion.Comment: Accepted for publication in The Astrophysical Journal; 28 pages, 15
figure
Probing the Magnetized Interstellar Medium Surrounding the Planetary Nebula Sh 2-216
We present 1420 MHz polarization images of a 2.5 X 2.5 degree region around
the planetary nebula (PN) Sh 2-216. The images are taken from the Canadian
Galactic Plane Survey (CGPS). An arc of low polarized intensity appears
prominently in the north-east portion of the visible disk of Sh 2-216,
coincident with the optically identified interaction region between the PN and
the interstellar medium (ISM). The arc contains structural variations down to
the ~1 arcminute resolution limit in both polarized intensity and polarization
angle. Several polarization-angle "knots" appear along the arc. By comparison
of the polarization angles at the centers of the knots and the mean
polarization angle outside Sh 2-216, we estimate the rotation measure (RM)
through the knots to be -43 +/- 10 rad/m^2. Using this estimate for the RM and
an estimate of the electron density in the shell of Sh 2-216, we derive a
line-of-sight magnetic field in the interaction region of 5.0 +/- 2.0 microG.
We believe it more likely the observed magnetic field is interstellar than
stellar, though we cannot completely dismiss the latter possibility. We
interpret our observations via a simple model which describes the ISM magnetic
field around Sh 2-216, and comment on the potential use of old PNe as probes of
the magnetized ISM.Comment: 25 pages, 4 figures. Accepted for publication in the Astrophysical
Journa
Sustainable institutionalized punishment requires elimination of second-order free-riders
Although empirical and theoretical studies affirm that punishment can elevate
collaborative efforts, its emergence and stability remain elusive. By
peer-punishment the sanctioning is something an individual elects to do
depending on the strategies in its neighborhood. The consequences of
unsustainable efforts are therefore local. By pool-punishment, on the other
hand, where resources for sanctioning are committed in advance and at large,
the notion of sustainability has greater significance. In a population with
free-riders, punishers must be strong in numbers to keep the "punishment pool"
from emptying. Failure to do so renders the concept of institutionalized
sanctioning futile. We show that pool-punishment in structured populations is
sustainable, but only if second-order free-riders are sanctioned as well, and
to a such degree that they cannot prevail. A discontinuous phase transition
leads to an outbreak of sustainability when punishers subvert second-order
free-riders in the competition against defectors.Comment: 7 two-column pages, 3 figures; accepted for publication in Scientific
Report
Benevolent characteristics promote cooperative behaviour among humans
Cooperation is fundamental to the evolution of human society. We regularly
observe cooperative behaviour in everyday life and in controlled experiments
with anonymous people, even though standard economic models predict that they
should deviate from the collective interest and act so as to maximise their own
individual payoff. However, there is typically heterogeneity across subjects:
some may cooperate, while others may not. Since individual factors promoting
cooperation could be used by institutions to indirectly prime cooperation, this
heterogeneity raises the important question of who these cooperators are. We
have conducted a series of experiments to study whether benevolence, defined as
a unilateral act of paying a cost to increase the welfare of someone else
beyond one's own, is related to cooperation in a subsequent one-shot anonymous
Prisoner's dilemma. Contrary to the predictions of the widely used inequity
aversion models, we find that benevolence does exist and a large majority of
people behave this way. We also find benevolence to be correlated with
cooperative behaviour. Finally, we show a causal link between benevolence and
cooperation: priming people to think positively about benevolent behaviour
makes them significantly more cooperative than priming them to think
malevolently. Thus benevolent people exist and cooperate more
Breakdown of Conformal Invariance at Strongly Random Critical Points
We consider the breakdown of conformal and scale invariance in random systems
with strongly random critical points. Extending previous results on
one-dimensional systems, we provide an example of a three-dimensional system
which has a strongly random critical point. The average correlation functions
of this system demonstrate a breakdown of conformal invariance, while the
typical correlation functions demonstrate a breakdown of scale invariance. The
breakdown of conformal invariance is due to the vanishing of the correlation
functions at the infinite disorder fixed point, causing the critical
correlation functions to be controlled by a dangerously irrelevant operator
describing the approach to the fixed point. We relate the computation of
average correlation functions to a problem of persistence in the RG flow.Comment: 9 page
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