1,089 research outputs found
On the Origin of Risk Sensitivity: the Energy Budget Rule Revisited
The risk-sensitive foraging theory formulated in terms of the (daily) energy
budget rule has been influential in behavioural ecology as well as other
disciplines. Predicting risk-aversion on positive budgets and risk-proneness on
negative budgets, however, the budget rule has recently been challenged both
empirically and theoretically. In this paper, we critically review these
challenges as well as the original derivation of the budget rule and propose a
`gradual' budget rule, which is normatively derived from a gradual nature of
risk sensitivity and encompasses the conventional budget rule as a special
case. The gradual budget rule shows that the conventional budget rule holds
when the expected reserve is close enough to a threshold for overnight
survival, selection pressure being significant. The gradual view also reveals
that the conventional budget rule does not need to hold when the expected
reserve is not close enough to the threshold, selection pressure being
insignificant. The proposed gradual budget rule better fits the empirical
findings including those that used to challenge the conventional budget rule.Comment: 13 pages, 4 figure
Stochastic Evolutionary Dynamics of Trust Games with Asymmetric Parameters
Trusting in others and reciprocating that trust with trustworthy actions are
crucial to successful and prosperous societies. The Trust Game has been widely
used to quantitatively study trust and trustworthiness, involving a sequential
exchange between an investor and a trustee. The deterministic evolutionary game
theory predicts no trust and no trustworthiness whereas the behavioural
experiments with the one-shot anonymous Trust Game show that people
substantially trust and respond trustworthily. To explain these discrepancies,
previous works often turn to additional mechanisms, which are borrowed from
other games such as Prisoner's Dilemma. Although these mechanisms lead to the
evolution of trust and trustworthiness to an extent, the optimal or the most
common strategy often involves no trustworthiness. In this paper, we study the
impact of asymmetric demographic parameters (e.g. different population sizes)
on game dynamics of the Trust Game. We show that, in weak-mutation limit,
stochastic evolutionary dynamics with the asymmetric parameters can lead to the
evolution of high trust and high trustworthiness without any additional
mechanisms in well-mixed finite populations. Even full trust and near full
trustworthiness can be the most common strategy. These results are
qualitatively different from those of the previous works. Our results thereby
demonstrate rich evolutionary dynamics of the asymmetric Trust Game.Comment: 17 pages, 15 figure
Somoclu: An Efficient Parallel Library for Self-Organizing Maps
Somoclu is a massively parallel tool for training self-organizing maps on
large data sets written in C++. It builds on OpenMP for multicore execution,
and on MPI for distributing the workload across the nodes in a cluster. It is
also able to boost training by using CUDA if graphics processing units are
available. A sparse kernel is included, which is useful for high-dimensional
but sparse data, such as the vector spaces common in text mining workflows.
Python, R and MATLAB interfaces facilitate interactive use. Apart from fast
execution, memory use is highly optimized, enabling training large emergent
maps even on a single computer.Comment: 26 pages, 9 figures. The code is available at
https://peterwittek.github.io/somoclu
Satisfied-defect, unsatisfied-cooperate: An evolutionary dynamics of cooperation led by aspiration
Evolutionary game theory has been widely used to study the evolution of
cooperation in social dilemmas where imitation-led strategy updates are
typically assumed. However, results of recent behavioral experiments are not
compatible with the predictions based on the imitation dynamics, casting doubts
on the assumption of the imitation-led updates and calling for alternative
mechanisms of strategy updates. An aspiration-led update is often considered as
an alternative to the imitation-led one. While details of update rules can have
significant impacts on the evolutionary outcomes and many variations in
imitation-led updates are thus studied, however, few variations exist in
aspiration-led updates. We introduce an aspiration-led update mechanism
("Satisfied-Defect, Unsatisfied-Cooperate") that is psychologically intuitive
and can yield a behavior richer than the conventional aspiration-led update
does in Prisoner's Dilemma games. Using analytical and numerical methods, we
study and link the stochastic dynamics of it in well-mixed finite populations
and the deterministic dynamics of infinite populations.Comment: 13 pages, 10 figures, and 3 table
Difference in the color stability of direct and indirect resin composites
Indirect resin composites are generally regarded to have better color stability than direct resin composites since they possess higher conversion degree. OBJECTIVE: The present study aimed at comparing the changes in color (ΔE) and color coordinates (ΔL, Δa and Δb) of one direct (Estelite Sigma: 16 shades) and 2 indirect resin composites (BelleGlass NG: 16 shades; Sinfony: 26 shades) after thermocycling. MATERIAL AND METHODS: Resins were packed into a mold and light cured; post-curing was performed on indirect resins. Changes in color and color coordinates of 1-mm-thick specimens were determined after 5,000 cycles of thermocycling on a spectrophotometer. RESULTS: ΔE values were in the range of 0.3 to 1.2 units for direct resins, and 0.3 to 1.5 units for indirect resins, which were clinically acceptable (Δ
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