scholarly journals Cooperation is less likely to evolve in a finite population with a highly skewed distribution of family size

2007 ◽  
Vol 274 (1620) ◽  
pp. 1861-1865 ◽  
Author(s):  
Sabin Lessard
Keyword(s):  
Family Size ◽  
Finite Population ◽  
General Rule ◽  
Skewed Distribution ◽  
Evolution Of Cooperation ◽  
Weak Selection ◽  
Time Step ◽  
Pairwise Interactions ◽  
Tit For Tat ◽  
The One

In the context of the finitely repeated Prisoner's Dilemma with the possibility of cooperating or defecting each time, the strategy tit-for-tat (TFT) consists in cooperating the first time and copying the strategy previously used by the opponent the next times. Assuming random pairwise interactions in a finite population of always defecting individuals, TFT can be favoured by selection to go to fixation following its introduction as a mutant strategy. We deduce the condition for this to be the case under weak selection in the framework of a general reproduction scheme in discrete time. In fact, we show when and why the one-third rule for the evolution of cooperation holds, and how it extends to a more general rule. The condition turns out to be more stringent when the numbers of descendants left by the individuals from one time-step to the next may substantially differ. This suggests that the evolution of cooperation is made more difficult in populations with a highly skewed distribution of family size. This is illustrated by two examples.

scholarly journals Evolutionary dynamics with game transitions

2019 ◽  
Vol 116 (51) ◽  
pp. 25398-25404 ◽  
Author(s):  
Qi Su ◽  
Alex McAvoy ◽  
Long Wang ◽  
Martin A. Nowak
Keyword(s):  
Strong Influence ◽  
Evolutionary Dynamics ◽  
Simple Game ◽  
Structured Populations ◽  
Evolution Of Cooperation ◽  
Altruistic Behavior ◽  
Weak Selection ◽  
Time Step ◽  
Mutual Cooperation ◽  
Connected Populations

The environment has a strong influence on a population’s evolutionary dynamics. Driven by both intrinsic and external factors, the environment is subject to continual change in nature. To capture an ever-changing environment, we consider a model of evolutionary dynamics with game transitions, where individuals’ behaviors together with the games that they play in one time step influence the games to be played in the next time step. Within this model, we study the evolution of cooperation in structured populations and find a simple rule: Weak selection favors cooperation over defection if the ratio of the benefit provided by an altruistic behavior, b, to the corresponding cost, c, exceedsk−k′, where k is the average number of neighbors of an individual andk′captures the effects of the game transitions. Even if cooperation cannot be favored in each individual game, allowing for a transition to a relatively valuable game after mutual cooperation and to a less valuable game after defection can result in a favorable outcome for cooperation. In particular, small variations in different games being played can promote cooperation markedly. Our results suggest that simple game transitions can serve as a mechanism for supporting prosocial behaviors in highly connected populations.

scholarly journals A comparison of two methods for predicting changes in the distribution of gene frequency when selection is applied repeatedly to a finite population

1969 ◽  
Vol 13 (2) ◽  
pp. 117-126 ◽  
Author(s):  
Derek J. Pike
Keyword(s):  
Iterative Procedure ◽  
Gene Frequency ◽  
Finite Population ◽  
Transition Matrices ◽  
Single Cycle ◽  
Gene Frequencies ◽  
Mean And Variance ◽  
The Mean ◽  
The One ◽  
Selection Of

Robertson (1960) used probability transition matrices to estimate changes in gene frequency when sampling and selection are applied to a finite population. Curnow & Baker (1968) used Kojima's (1961) approximate formulae for the mean and variance of the change in gene frequency from a single cycle of selection applied to a finite population to develop an iterative procedure for studying the effects of repeated cycles of selection and regeneration. To do this they assumed a beta distribution for the unfixed gene frequencies at each generation.These two methods are discussed and a result used in Kojima's paper is proved. A number of sets of calculations are carried out using both methods and the results are compared to assess the accuracy of Curnow & Baker's method in relation to Robertson's approach.It is found that the one real fault in the Curnow-Baker method is its tendency to fix too high a proportion of the genes, particularly when the initial gene frequency is near to a fixation point. This fault is largely overcome when more individuals are selected. For selection of eight or more individuals the Curnow-Baker method is very accurate and appreciably faster than the transition matrix method.

Definiteness and Voice in the Interpretation of Active and Passive Sentences

1975 ◽  
Vol 27 (2) ◽  
pp. 323-330 ◽  
Author(s):  
Michel Hupet ◽  
Brigitte Le Bouedec
Keyword(s):  
General Rule ◽  
Grammatical Subject ◽  
The One ◽  
The Voice

In Experiment I, subjects were given active and passive sentences where the definiteness of nominals is varied and about which uncertainty was expressed, e.g. “I thought that the policeman had been injured by a gangster, but I was mistaken, in fact.”. Their task was to decide what was the target of the mistake by completing freely the sentence in such a way that the account would be corrected. When the nominals are differentially determined (a-the, the-a), the pattern of responses indicates that, for both active and passive, subjects were more likely to conclude that it was the non-definitely marked nominal that had been involved in the mistake rather than the definitely marked one. When both nominals are similarly determined (a-a, the-the), subjects were more likely to indicate the event itself as having been involved in the mistake. This supports the hypothesis that subjects are able to utilize definiteness to determine the relation between presupposed and assertional information. In Experiment II, subjects were given paired active and passive sentences with differentially determined nominals and were required to choose between the two syntactic forms of each pair the one they would prefer to use. The pattern of responses clearly shows that subjects were more likely to choose the voice allowing the hypothesized preferential order “Definitely marked grammatical subject-non-definitely marked grammatical object”. Passive transformational rule is thus interpreted as a particular case of a more general rule specifying the ways in which what is made known (comment) is nested on to what is already assumed to be the case (topic).

scholarly journals Comparison of numerical schemes of river flood routing with an inertial approximation of the Saint Venant equations

RBRH ◽  
2018 ◽  
Vol 23 (0) ◽  
Author(s):  
Alice César Fassoni-Andrade ◽  
Fernando Mainardi Fan ◽  
Walter Collischonn ◽  
Artur César Fassoni ◽  
Rodrigo Cauduro Dias de Paiva
Keyword(s):  
Numerical Stability ◽  
Flood Routing ◽  
Computational Time ◽  
Numerical Schemes ◽  
Time Step ◽  
Simple Formulation ◽  
One Dimensional ◽  
Saint Venant Equations ◽  
Original Scheme ◽  
The One

ABSTRACT The one-dimensional flow routing inertial model, formulated as an explicit solution, has advantages over other explicit models used in hydrological models that simplify the Saint-Venant equations. The main advantage is a simple formulation with good results. However, the inertial model is restricted to a small time step to avoid numerical instability. This paper proposes six numerical schemes that modify the one-dimensional inertial model in order to increase the numerical stability of the solution. The proposed numerical schemes were compared to the original scheme in four situations of river’s slope (normal, low, high and very high) and in two situations where the river is subject to downstream effects (dam backwater and tides). The results are discussed in terms of stability, peak flow, processing time, volume conservation error and RMSE (Root Mean Square Error). In general, the schemes showed improvement relative to each type of application. In particular, the numerical scheme here called Prog Q(k+1)xQ(k+1) stood out presenting advantages with greater numerical stability in relation to the original scheme. However, this scheme was not successful in the tide simulation situation. In addition, it was observed that the inclusion of the hydraulic radius calculation without simplification in the numerical schemes improved the results without increasing the computational time.

scholarly journals Reciprocal innervation and symmetrical muscles

1913 ◽  
Vol 86 (587) ◽  
pp. 219-232 ◽  
Keyword(s):  
Skeletal Muscles ◽  
Knee Extensor ◽  
General Rule ◽  
The Body ◽  
Ordinary Sense ◽  
Excitatory Effect ◽  
Biological Meaning ◽  
Vasomotor Reflexes ◽  
The One ◽  
The Right

If we attempt to decipher the biological meaning of reciprocal innervation its various instances when marshalled together say plainly that one of the functional problems which it meets and solves is mechanical antagonism. Where two muscles have directly opposed effect on the same lever, “reciprocal innervation” is the general rule observed by the nervous system in dealing with them, and this holds whether the reciprocal innervation is peripheral as with the antagonists of the arthropod claw, or is central as with vertebrate skeletal muscles. Also where one and the same muscle is governed by two nerves influencing it oppositely, reciprocal innervation seems again the principle followed in the co-ordination of the two opponent centres, as has been shown by Bayliss in his observations on vasomotor reflexes. But the distribution and occurrence of reciprocal innervation extend beyond cases of mere mechanical antagonism. The reflex influence exerted by the limb-afferents on symmetrical muscle-pairs such as right knee-extensor and left is reciprocal. Thus right peroneal nerve excites the motoneurones of left vastocrureus, and concomitantly inhibits those of the right. The reflex inhibition of the one is concurrent with, increases with increase, and decreases with decrease of, the excitatory effect on the other. Here the muscles are not in any ordinary sense antagonistic; not only do they not operate on the same lever, but they are not even members of the same limb, nor do they belong even to the same half of the body. They are, however, actuated conversely in the most usual modes of progression—the walking and the running step—though not always in galloping.

scholarly journals Should you save the more useful? The effect of generality on moral judgments about rescue and indirect effects

2020 ◽  
Author(s):  
Lucius Caviola ◽  
Stefan Schubert ◽  
Andreas Mogensen
Keyword(s):  
Indirect Effects ◽  
General Rule ◽  
Moral Dilemmas ◽  
Moral Judgments ◽  
Social Utility ◽  
Negative Consequences ◽  
General Phenomenon ◽  
Unemployed People ◽  
General Rules ◽  
The One

Across eight experiments (N = 2,310), we studied whether people would prioritize rescuing individuals who may be thought to contribute more to society. We found that participants were generally dismissive of general rules that prioritize more socially beneficial individuals, such as doctors instead of unemployed people. By contrast, participants were more supportive of one-off decisions to save the life of a more socially beneficial individual, even when such cases were the same as those covered by the rule. This generality effect occurred robustly even when controlling for various factors. It occurred when the decision-maker was the same in both cases, when the pairs of people differing in the extent of their indirect social utility was varied, when the scenarios were varied, when the participant samples came from different countries, and when the general rule only covered cases that are exactly the same as the situation described in the one-off condition. The effect occurred even when the general rule was introduced via a concrete precedent case. Participants’ tendency to be more supportive of the one-off proposal than the general rule was significantly reduced when they evaluated the two proposals jointly as opposed to separately. Finally, the effect also occurred in sacrificial moral dilemmas, suggesting it is a more general phenomenon in certain moral contexts. We discuss possible explanations of the effect, including concerns about negative consequences of the rule and a deontological aversion against making difficult trade-off decisions unless they are absolutelynecessary.

TIT FOR TAT in sticklebacks and the evolution of cooperation

Nature ◽  
1987 ◽  
Vol 325 (6103) ◽  
pp. 433-435 ◽  
Author(s):  
Manfred Milinski
Keyword(s):  
Evolution Of Cooperation ◽  
Tit For Tat

Deployment, calibration, and efficiency of SHUD model in cold and arid watersheds

2021 ◽  
Author(s):  
Lele Shu ◽  
Hao Chen ◽  
Xianhong Meng
Keyword(s):  
Water Movement ◽  
Yellow River ◽  
Hydrologic Model ◽  
Data Availability ◽  
Heihe River ◽  
Time Step ◽  
Subsurface Hydrology ◽  
The Usa ◽  
The One ◽  
Global Datasets

<p>The hydrologic model is ideal for experimenting and understanding the water movement and storage in a watershed from the upper mountain to the river outlet. Nevertheless, the model's performance, suitability, and data availability are the primary challenge for a modeler. This study introduces the Simulator for Hydrologic Unstructured Domains (SHUD), a surface-subsurface integrated hydrological model using the semi-discrete Finite Volume Method. Though the SHUD applies a fine time-step (in minutes) and flexible spatial domain decomposition (m to km) to simulate the fully coupled surface-subsurface hydrology, the model can solve the watershed-scale problem efficiently and dependably. Plenty of applications in the USA proved the SHUD model's performance and suitability in the humid and data-rich watersheds.  </p><p>In this research, we demonstrate the SHUD model deployment in two data-scarce watersheds in the northwest of China with global datasets, validate the simulations against local observational data, and assess the SHUD model's efficiency and suitability.  The one is the Upstream Heihe River (UHR), which is a typical semi-arid mountainous watershed.  The other is Yellow River Source (YRS), the upstream of Yellow River, contributing more than 50% of total discharge. The results, figures, and analysis based on SHUD simulations under global datasets highlight the model's suitability and efficiency in data-limited watersheds, even ungaged ones. The SHUD model is a useful modeling platform for hydrology and water-related coupling studies.</p>

Special Topics in Queueing Theory

2018 ◽  
pp. 212-254
Keyword(s):  
Queueing Theory ◽  
Finite Population ◽  
Service Process ◽  
Batch Service ◽  
Priority Level ◽  
Priority System ◽  
Priority Systems ◽  
The One ◽  
Number Of Customers

Topics covered in Chapter 7 are priority systems with preemptive or non-preemptive system, systems with N classes of customers, customers in groups: bulk arrivals, batch service, balking and reneging, and finite population. In a priority system, it is assumed that there are 1, 2, 3, …, N different classes or types of customers, where Type 1 customers are the most important while class N ones are the least important. When a server is available to serve a customer from the queue, the one with the highest priority level will go to the server to start their service process. In batch service, before starting the service process, a group or batch needs to be formed with a certain number of customers.

scholarly journals A single acoustic beacon-based positioning method for underwater mobile recovery of an AUV

2018 ◽  
Vol 15 (5) ◽  
pp. 172988141880173 ◽  
Author(s):  
Ziye Zhou ◽  
Yanqing Jiang ◽  
Ye Li ◽  
Cao Jian ◽  
Yeyi Sun
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Dead Reckoning ◽  
Underwater Vehicle ◽  
Doppler Velocity ◽  
Fusion Algorithm ◽  
Time Step ◽  
Short Baseline ◽  
Positioning Method ◽  
One Step ◽  
The One

This article presents a navigation method for an autonomous underwater vehicle being recovered by a human-occupied vehicle. The autonomous underwater vehicle is considered to carry underwater navigation sensors such as ultra-short baseline, Doppler velocity log, and inertial navigation system. Using these sensors’ information, a navigation module combining the ultra-short baseline positioning and inertial positioning is established. In this study, there is assumed to be no communication between the autonomous underwater vehicle and human-occupied vehicle; thus, to obtain the autonomous underwater vehicle position in the inertial coordinate, a conjecture method to obtain the human-occupied vehicle coordinates is proposed. To reduce the error accumulation of autonomous underwater vehicle navigation, a method called one-step dead reckoning positioning is proposed, and the one-step dead reckoning positioning is treated as a correction to combine with ultra-short baseline positioning by a data fusion algorithm. One-step dead reckoning positioning is a positioning method based on the previous time-step coordinates of the autonomous underwater vehicle.

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