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We consider a time-continuous Markov branching process of proliferating cells with a countable collection of types. Among-type transitions are inspired by the Tug-of-War process introduced by McFarland et al. (Proc Natl Acad Sci 111(42):15138–15143, 2014) as a mathematical model for competition of advantageous driver mutations and deleterious passenger mutations in cancer cells. We introduce a version of the model in which a driver mutation pushes the type of the cell L-units up, while a passenger mutation pulls it 1-unit down. The distribution of time to divisions depends on the type (fitness) of cell, which is an integer. The extinction probability given any initial cell type is strictly less than 1, which allows us to investigate the transition between types (type transition) in an infinitely long cell lineage of cells. The analysis leads to the result that under driver dominance, the type transition process escapes to infinity, while under passenger dominance, it leads to a limit distribution. Implications in cancer cell dynamics and population genetics are discussed. [ABSTRACT FROM AUTHOR]

In a series of publications McFarland and co-authors introduced the tug-of-war model of evolution of cancer cell populations. The model is explaining the joint effect of rare advantageous and frequent slightly deleterious mutations, which may be identifiable with driver and passenger mutations in cancer. In this paper, we put the tug-of-war model in the framework of a denumerable-type Moran process and use mathematics and simulations to understand its behavior. The model is associated with a time-continuous Markov Chain (MC), with a generator that can be split into a sum of the drift and selection process part and of the mutation process part. Operator semigroup theory is then employed to prove that the MC does not explode, as well as to characterize a strong-drift limit version of the MC which displays 'instant fixation' effect, which was an assumption in the original McFarland's model. Mathematical results are confirmed by simulations of the complete and limit versions. Simulations also visualize complex stochastic transients and genealogies of clones arising in the model. [ABSTRACT FROM AUTHOR]

The tug-of-war in which single players repeatedly compete in all-pay auctions is known to have a non-cooperative Markov-perfect equilibrium in which neither player expends positive effort and the tug-of-war remains unresolved, provided that the winner and loser prizes, the tie-breaking rule, the lead required for victory, and the initial state are chosen appropriately. In this paper, we show that such peaceful equilibria do not exist if the tug-of-war is between teams with pairwise matched players. The reason for this phenomenon is that the members of the teams can externalize future effort costs while the single players cannot. For a restricted number of states, our analysis also highlights the impact of the discount factor on the expected trajectory of the tug-of-war, the dynamics of the expected effort, and the equilibrium utility. [ABSTRACT FROM AUTHOR]

Ring‐opening copolymerizations have emerged as a powerful approach towards the creation of sustainable polymers. Typical H‐bonding catalysts for ring‐opening are subject to a single catalytic site. Here we describe a H‐bond‐donor/Lewis‐acidic‐boron organocatalyst featuring two distinct catalytic sites in one molecule. The ring‐opening copolymerization of epoxides with anhydride mediated by these modular, and tunable catalysts achieves high selectivity (>99 % polyester selectivity) and markedly higher activity compared to either of the di‐thiourea analogues or any combinations of them. Calculations and experimental studies reveal that the superior catalytic performance arises from tug‐of‐war between two differentiated catalytic sites: thiourea pulls off the propagating chain‐end from boron center, simultaneously enhancing the role of monomer activation and also nucleophilicity of the propagation intermediates. [ABSTRACT FROM AUTHOR]

The spatial organization of the cell depends upon intracellular trafficking of cargos hauled along microtubules and actin filaments by the molecular motor proteins kinesin, dynein, and myosin. Although much is known about how single motors function, there is significant evidence that cargos in vivo are carried by multiple motors. While some aspects of multiple motor function have received attention, how the cargo itself - and motor organization on the cargo-affects transport has not been considered. To address this, we have developed a three-dimensional Monte Carlo simulation of motors transporting a spherical cargo, subject to thermal fluctuations that produce both rotational and translational diffusion. We found that these fluctuations could exert a load on the motor(s), significantly decreasing the mean travel distance and velocity of large cargos, especially at large viscosities. In addition, the presence of the cargo could dramatically help the motor to bind productively to the microtubule: the relatively slow translational and rotational diffusion of moderately sized cargos gave the motors ample opportunity to bind to a microtubule before the motor/cargo ensemble diffuses out of range of that microtubule. For rapidly diffusing cargos, the probability of their binding to a microtubule was high if there were nearby microtubules that they could easily reach by translational diffusion. Our simulations found that one reason why motors may be approximately 100 nm long is to improve their 'on' rates when attached to comparably sized cargos. Finally, our results suggested that to efficiently regulate the number of active motors, motors should be clustered together rather than spread randomly over the surface of the cargo. While our simulation uses the specific parameters for kinesin, these effects result from generic properties of the motors, cargos, and filaments, so they should apply to other motors as well.

The maintenance of intracellular processes, like organelle transport and cell division, depend on bidirectional movement along microtubules. These processes typically require kinesin and dynein motor proteins, which move with opposite directionality. Because both types of motors are often simultaneously bound to the cargo, regulatorymechanisms are required to ensure controlled directional transport. Recently, it has been shown that parameters like mechanical motor activation, ATP concentration and roadblocks on the microtubule surface differentially influence the activity of kinesin and dynein motors in distinct manners. However, how these parameters affect bidirectional transport systems has not been studied. Here, we investigate the regulatory influence of these three parameters using in vitro gliding motility assays and stochastic simulations. We find that the number of active kinesin and dynein motors determines the transport direction and velocity, but that variations in ATP concentration and roadblock density have no significant effect. Thus, factors influencing the force balance between opposite motors appear to be important, whereas the detailed stepping kinetics and bypassing capabilities of the motors only have a small effect. [ABSTRACT FROM AUTHOR]

Cooperative breeding often results in unequal reproduction between dominant and subordinate group members. Transactional skew models attempt to predict how unequal reproduction can be before the groups themselves become unstable. A number of variants of transactional models have been developed, with a key difference being whether reproduction is controlled by one party or contested by all. It is shown here that ESS solutions for all situations of contested control over reproduction are given by the original tug-of-war model (TOW). Several interesting results follow. First, TOW can escalate enough to destabilize some types of groups. Particularly vulnerable are those that have low relatedness and gain little from cooperative breeding relative to solitary reproduction. Second, TOW can drastically reduce group productivity and especially the inclusive fitness of dominant individuals. Third, these results contrast strongly with those from variants of TOW models that include concessions to maintain group stability. Such models are shown to be special cases of the general and simpler TOW framework, and to have assumptions that may be biologically suspect. Finally, the overall analysis suggests that there is no mechanism within existing TOW framework that will prevent a costly struggle for reproductive control. Because social species rarely exhibit the high levels of aggression predicted by TOW models, alternative evolutionary mechanisms are considered that can limit conflict and produce more mutually beneficial outcomes. The further development of alternative models to predict patterns of reproductive skew are highly recommended.

It is often assumed in biophysical studies that when multiple identical molecular motors interact with two parallel microtubules, the microtubules will be crosslinked and locked together. The aim of this study is to examine this assumption mathematically. We model the forces and movements generated by motors with a time-continuous Markov process and find that, counter-intuitively, a tug-of-war results from opposing actions of identical motors bound to different microtubules. The model shows that many motors bound to the same microtubule generate a great force applied to a smaller number of motors bound to another microtubule, which increases detachment rate for the motors in minority, stabilizing the directional sliding. However, stochastic effects cause occasional changes of the sliding direction, which has a profound effect on the character of the long-term microtubule motility, making it effectively diffusion-like. Here, we estimate the time between the rare events of switching direction and use them to estimate the effective diffusion coefficient for the microtubule pair. Our main result is that parallel microtubules interacting with multiple identical motors are not locked together, but rather slide bidirectionally. We find explicit formulae for the time between directional switching for various motor numbers. [ABSTRACT FROM AUTHOR]

The transportation of a colossus painted in the ancient Egyptian tomb of Djehutihotep (Dayr al-Barsha) is known as an example of lubrication application. However the benefits and the nature of lubrication used by ancient Egyptians are controversial. In order to clarify this issue, the physical parameters involved in the transportation are carefully reviewed. The traction force is a key parameter, and is evaluated by simple physical models and the results of biomechanical and ergonomic studies. The results of this work suggest high traction force can be produced only with an excellent team coordination, and the friction coefficient between sledge and ground is efficiently reduced by hypothetical methods which exclude probably wood-on-wood or wood-on-sand surface contacts.

We establish regularity for functions satisfying a dynamic programming equation, which may arise for example from stochastic games or discretization schemes. Our results can also be utilized in obtaining regularity and existence results for the corresponding partial differential equations. [ABSTRACT FROM AUTHOR]

Abstract The Devil’s Advocate and the chilling effect: Territorial games with law in the flowzone. The right of self-regulation has been a fundamentally important goal in the struggle of the Norwegian press for increased freedom. The article describes how self-regulation has established a seemingly robust societal position despite periods of heavy criticism. The author singles out politicians and jurists as the potentially most powerful norm senders, and describes the press freedom game as a tug-of-war between politics, the law and journalism. By the end of the 20th century, attacks from the political branch had been neutralized by the press, seemingly with lasting effect. Since then, international law (Strasbourg) has played an increasingly important role, directly and by way of infiltration of the norms of journalism. The press may be pushed in the direction of a real, if not formal, juridification.

A paddler requires not only flexibility and strength for heavy paddling, but also muscular endurance to maintain stamina for an entire session. In creating an effective endurance program of cardiovascular activities, four elements are critical. Increasing or upgrading any one of these elements will increase the demands placed on your body as it works to develop the cardiovascular fitness essential to endurance. These elements are: Frequency - the number of times the endurance exercise is performed in a particular period of time; Duration - the length of time it takes to perform the exercise; Intensity - the effort level reached during the exercise; Type - the choice of exercise performed in a workout. [ABSTRACT FROM AUTHOR]

This paper analyzes a tug-of-war contest between two teams. In each round of the tug-of-war, a pair of agents from the opposing teams competes in a private value all-pay auction with asymmetric value distributions and effort effectiveness. Whichever team arrives first at a given lead in terms of battle victories over the opponent wins the tug-of-war. There exists a unique Markov-perfect equilibrium in bidding strategies which depend on the respective player's valuation and the current state of the tug-of-war. We derive rich comparative statics for this equilibrium by using the fact that the state of the tug-of-war evolves according to a time-homogeneous absorbing Markov chain. [ABSTRACT FROM AUTHOR]

We study a two player zero-sum tug-of-war game with varying probabilities that depend on the game location x. In particular, we show that the value of the game is locally asymptotically Hölder continuous. The main difficulty is the loss of translation invariance. We also show the existence and uniqueness of values of the game. As an application, we prove that the value function of the game converges to a viscosity solution of the normalized p(x)-Laplacian. [ABSTRACT FROM AUTHOR]

We develop an option pricing model based on a tug-of-war game. This two-player zero-sum stochastic differential game is formulated in the context of a multidimensional financial market. The issuer and the holder try to manipulate asset price processes in order to minimize and maximize the expected discounted reward. We prove that the game has a value and that the value function is the unique viscosity solution to a terminal value problem for a parabolic partial differential equation involving the nonlinear and completely degenerate infinity Laplace operator. [ABSTRACT FROM AUTHOR]

We derive the weakly coupled systems of the infinity Laplace equations via a tug-of-war game introduced by Peres, Schramm, Sheffield, and Wilson (2009). We establish existence, uniqueness results of the solutions, and introduce a new notion of "generalized cones" for systems. By using "generalized cones" we analyze blow-up limits of solutions. [ABSTRACT FROM AUTHOR]

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We study local regularity properties of value functions of time-dependent tug-of-war games. For games with constant probabilities we get local Lipschitz continuity. For more general games with probabilities depending on space and time we obtain Hölder and Harnack estimates. The games have a connection to the normalized p ( x , t ) -parabolic equation u t = Δ u + ( p ( x , t ) − 2 ) Δ ∞ N u . [ABSTRACT FROM AUTHOR]

Ownership can evolve in potentially any species. Drawing on insights from across disciplines, we distinguish between possession and ownership and present species-neutral criteria for ownership, defined as respect for possession. We use a variant of the tug-of-war evolutionary game to demonstrate how ownership can evolve in the form of a new, biologically realistic strategy, Restraint With Retaliation ( RWR). In our game, resource holding potential ( RHP) is assumed to be equal between interactants, and resource holding asymmetry determines whether ownership is adaptive. RWR will be evolutionarily stable when the ratio of resource holdings between interactants is relatively low, but not when this ratio is sufficiently high. We offer RWR as one evolutionary route to ownership among many, and discuss how ownership unites previously described behavioural phenomena across taxa. We propose that some but not all mechanisms of territory formation and maintenance can be considered ownership, and show that territories are not the only resources that can be owned. We argue that ownership can be a powerful cooperative solution to tragedies of the commons and problems of collective action throughout the biological world. We advance recent scholarship that has begun to investigate the biological importance of ownership, and we call for a comprehensive account of its evolutionary logic and taxonomic distribution. We propose that ownership should be considered a fundamental, unifying biological phenomenon. [ABSTRACT FROM AUTHOR]

Social animals vary in their ability to compete with group members over shared resources and also vary in their cooperative efforts to produce these resources. Competition among groups can promote within-group cooperation, but many existing models of intergroup cooperation do not explicitly account for observations that group members invest differentially in cooperation and that there are often within-group competitive or power asymmetries. We present a game theoretic model of intergroup competition that investigates how such asymmetries affect within-group cooperation. In this model, group members adopt one of two roles, with relative competitive efficiency and the number of individuals varying between roles. Players in each role make simultaneous, coevolving decisions. The model predicts that although intergroup competition increases cooperative contributions to group resources by both roles, contributions are predominantly from individuals in the less competitively efficient role, whereas individuals in the more competitively efficient role generally gain the larger share of these resources. When asymmetry in relative competitive efficiency is greater, a group's per capita cooperation (averaged across both roles) is higher, due to increased cooperation from the competitively inferior individuals. For extreme asymmetry in relative competitive efficiency, per capita cooperation is highest in groups with a single competitively superior individual and many competitively inferior individuals, because the latter acquiesce and invest in cooperation rather than within-group competition. These predictions are consistent with observed features of many societies, such as monogynous Hymenoptera with many workers and caste dimorphism. [ABSTRACT FROM AUTHOR]

We prove local Lipschitz continuity and Harnack's inequality for value functions of the stochastic game tug-of-war with noise and running payoff. As a consequence, we obtain game-theoretic proofs for the same regularity properties for viscosity solutions of the inhomogeneous p-Laplace equation when p > 2. [ABSTRACT FROM AUTHOR]

The object of analysis in this work is a child’s game which is widely spread throughout Europe. Special consideration is given to the variants of the game which include the following moments: two players form a double bridge /gate with their raised arms; the other participants go beneath the raised arms while holding on to each other’s clothes or waist; one by one the players are held back and are required to say one of the passwords suggested by the players forming the bridge /gate; the game ends with a tug-of-war between the two teams. Based on a detailed analysis of the playing of the game, as well as on some peculiarities of the texts related to it, a conclusion can be reached that this type of game is a successor of the ritual combat, typically performed during season change or in the beginning of the New Year. [ABSTRACT FROM AUTHOR]

• Stochastic and deterministic models both describe motor-driven filament transport. • Comparing stochastic and deterministic forms assesses the impact of intrinsic noise. • Discrepancies between multi-stable deterministic and stochastic models emerge. • Intrinsic noise helps coordinate polarized transport of filament ensemble. • In biological systems, motor binding properties are a major regulatory mechanism. [Display omitted] Noise affects all biological processes from molecules to cells, organisms and populations. Although the effect of noise on these processes is highly variable, evidence is accumulating which shows natural stochastic fluctuations (noise) can facilitate biological functions. Herein, we investigate the effect of noise on the transport of intermediate filaments in cells by comparing the stochastic and deterministic formalizations of the bidirectional transport of intermediate filaments, long elastic polymers transported along microtubules by antagonistic motor proteins (Dallon et al., 2019; Portet et al., 2019). By numerically exploring discrepancies in timescales and attractors between both formalizations, we characterize the impact of stochastic fluctuations on the individual and ensemble transport. Biologically, we find that noise promotes the collective movement of intermediate filaments and increases the efficiency of its regulation by the biochemical properties of motor-cargo interactions. While stochastic fluctuations reduce the impact of the initial distributions of motor proteins in cells, the number of binding sites and the affinity of motor-cargo interactions are the key parameters controlling transport efficiency and efficacy. [ABSTRACT FROM AUTHOR]

Multimale groups of primates are characterized by strong reproductive competition among males, generally resulting in an uneven division of male reproductive success (reproductive skew). The observed patterns of conflict and reproductive skew have often been attributed to the so-called tug-of-war model. We show, however, that two important assumptions of this model are not met in male primates. First, the tug-of-war model assumes that reproductive conflict reduces overall group productivity, but in male primates (and most other vertebrates) conflict likely involves mortality rather than fecundity costs. Second, the tug-of-war model does not account for the possibility that male primates can achieve some reproductive success without engagement in open conflict, such as when a single male cannot guard several receptive females at the same time. We therefore develop a dynamic version of the tug-of-war model, in which reproductive competition causes mortality costs, and in which individuals can gain uncontested shares of reproduction dependent on the degree of female receptive overlap. This model differs substantially from the original tug-of-war model, and derives a new and rich set of comparative predictions. For instance, it predicts that the level of conflict among males declines as the queuing success of subordinate males increases (as survival increases), and also, as their uncontested share of reproduction increases, e.g., as female receptive overlap increases. Our model shows how male-male conflict and female receptive overlap collectively determine the level of reproductive skew among male primates, and illustrates that this relationship is more complex than previously thought. [ABSTRACT FROM AUTHOR]

Kinesin and dynein are fundamental components of intracellular transport, but their interactions when simultaneously present on cargos are unknown. We built an optical trap that can be calibrated in vivo during data acquisition for each individual cargo to measure forces in living cells. Comparing directional stall forces in vivo and in vitro, we found evidence that cytoplasmic dynein is active during minus- and plus-end directed motion, whereas kinesin is only active in the plus direction. In vivo, we found outward (~plus-end) stall forces range from 2 to 7 pN, which is significantly less than the 5-to 7-pN stall force measured in vitro for single kinesin molecules. In vitro measurements on beads with kinesin-1 and dynein bound revealed a similar distribution, implying that an interaction between opposite polarity motors causes this difference. Finally, inward (~minus-end) stalls in vivo were 2-3 pN, which is higher than the 1.1-pN stall force of a single dynein, implying multiple active dynein. [ABSTRACT FROM AUTHOR]

Using a solution of a nonhomogeneous partial differential equation involving the p-Laplacian, we study the finiteness of the expected time to end the tug-of-war in a wedge. [ABSTRACT FROM AUTHOR]

Many cellular cargoes move bidirectionally along microtubules, driven by teams of plus- and minus-end-directed motor proteins. To probe the forces exerted on cargoes during intracellular transport, we examined latex beads phagocytosed into living mammalian macrophages. These latex bead compartments (LBCs) are encased in membrane and transported along the cytoskeleton by a complement of endogenous kinesin-1, kinesin-2, and dynein motors. The size and refractive index of LBCs makes them well-suited for manipulation with an optical trap. We developed methods that provide in situ calibration of the optical trap in the complex cellular environment, taking into account any variations among cargoes and local viscoelastic properties of the cytoplasm. We found that centrally and peripherally directed forces exerted on LBCs are of similar magnitude, with maximum forces of ∼20 pN. During force events greater than 10 pN, we often observe 8-nm steps in both directions, indicating that the stepping of multiple motors is correlated. These observations suggest bidirectional transport of LBCs is driven by opposing teams of stably bound motors that operate near force balance. [ABSTRACT FROM AUTHOR]

We study a version of the stochastic “tug-of-war” game, played on graphs and smooth domains, with the empty set of terminal states. We prove that, when the running payoff function is shifted by an appropriate constant, the values of the game after n steps converge in the continuous case and the case of finite graphs with loops. Using this we prove the existence of solutions to the infinity Laplace equation with vanishing Neumann boundary condition. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper we study a general class of “quasilinear non-local equations” depending on the gradient which arises from tug-of-war games. We establish a regularity theory for these equations (the kind of regularity depending on the assumptions on the kernel), and we construct different non-local approximations of the -Laplacian. [Copyright &y& Elsevier]

Social organisms in many taxa cooperate to produce resources that are shared among group members. Some cooperatively produced resources may be monopolized by individuals who invest in within-group competition, but these have largely been overlooked in empirical and theoretical research on human cooperation, which has focused on noncontestable public goods. In this study, we allow for the potential of within-group competition over cooperatively produced resources and use a game theoretic “tug-of-war” model and empirical test to show that such competition decreases the degree of cooperation within human groups and hence decreases group members' payoffs. Our study thus sheds light on how cooperative production and equal division of shared resources may have evolved, expands on current models of human cooperation to reflect the many natural conditions with opportunities for within-group competition, and demonstrates unifying principles in cooperation and competition across the animal kingdom. [ABSTRACT FROM PUBLISHER]

Bidirectional transport along microtubules is ensured by opposing motor proteins: cytoplasmic dynein that drives cargo to the minus-ends and various kinesins that generally move to the plus-ends of microtubules. Regulation of motor proteins that are simultaneously bound to the same organelle is required to maintain directional transport and prevent pausing of cargo pulled away by motors of opposite polarity. Debates of the recent decade have been focused on two possible mechanisms of such regulation: (i) coordination, which implies that only one type of motors is active at a given time, and (ii) tug-of-war, which assumes that both motors are active at the same time and that direction of transport depends on the outcome of motor's confrontation. The initial idea of coordination has been challenged by observations of simultaneous activity of plus- and minus-end-directed motors applied to the same cargo. Analysis of the available data indicates that coordination and tug-of-war theories rather complement than contradict each other: cargo interacts with two teams of active motors, the resulting direction and the winner team are determined by coordination complexes, but the activity of the loser team is never completely inhibited and remains at some background level. Such persisting activity might enhance the overall efficiency of transport by increasing processivity or helping to overcome the obstacles on microtubule track. [ABSTRACT FROM AUTHOR]

We present a modified version of the two-player "tug-of-war" game introduced by Peres, Schramm, Sheffield, and Wilson (2009). This new tug-of- war game is identical to the original except near the boundary of the domain ??, but its associated value functions are more regular. The dynamic programming principle implies that the value functions satisfy a certain finite difference equation. By studying this difference equation directly and adapting techniques from viscosity solution theory, we prove a number of new results. We show that the finite difference equation has unique maximal and minimal solutions, which are identified as the value functions for the two tug-of-war players. We demonstrate uniqueness, and hence the existence of a value for the game, in the case that the running payoff functions is nonnegative. We also show that uniqueness holds in certain cases for sign-changing running payoff functions which are sufficiently small. In the limit ? ? 0, we obtain the convergence of the value functions to a viscosity solution of the normalized infinity Laplace equation. We also obtain several new results for the normalized infinity Laplace equation ???u = f. In particular, we demonstrate the existence of solutions to the Dirichlet problem for any bounded continuous f, and continuous boundary data, as well as the uniqueness of solutions to this problem in the generic case. We present a new elementary proof of uniqueness in the case that f > 0, f < 0, or f ? 0. The stability of the solutions with respect to f is also studied, and an explicit continuous dependence estimate from f ? 0 is obtained. [ABSTRACT FROM AUTHOR]

The purpose of this study was to collect heart rates of subjects by the polar team system heart rate monitor during the championship finals (3 rounds). Eight junior high school indoor tug-of-war athletes participated in the study. The percentage of heart rate reserve (%HRR) was calculated. During the competitions, the lowest heart rate of subjects were 34.5±6.4%HRR ∼ 50.8±7.0%HRR. The highest heart rate of subjects were 66.7±6.5%HRR ∼ 87.1±6.3%HRR and presented at the last stage of games for a few seconds. In conclusion, when teenage indoor tug-of-war player face contender of the weakness level, their intensity is 52.7±13.4 %HRR. Moreover, when they face contender the same level, their intensity is 72.7 ∼ 13.1%HRR. [ABSTRACT FROM AUTHOR]

In this paper, we study value functions of time-dependent tug-of-war games. We first prove the existence and uniqueness of value functions and verify that these game values satisfy a dynamic programming principle. Using the arguments in the proof of existence of game values, we can also deduce asymptotic behavior of game values when T → ∞. Furthermore, we investigate boundary regularity for game values. Thereafter, based on the regularity results for value functions, we deduce that game values converge to viscosity solutions of the normalized parabolic p -Laplace equation. [ABSTRACT FROM AUTHOR]

Abstract: Individual differences and causative factors could modify the behaviour of dogs in object related games played with a human partner. In a two-by-two within-subject design we observed 68 family dogs’ behaviour when playing two different types of games (ball game and tugging) with two different play partners (owner or unfamiliar experimenter) in order to categorize each dog''s playing style. In all four conditions we have measured the following behavioural variables: tendency for possession, willingness to retrieve, behaviours related to fear/avoidance and aggression, and occurrence of play bows. We also calculated the relative duration of time when the dogs oriented “outwards” from the play situation to the other non-interacting person (owner or experimenter) during a session. Than we examined the effect of six factors on dog–human play behaviour: the familiarity of the play partner, the type of the game, the dogs’ gender, age and breed, and the duration of daily active interaction between dog and owner. We used factor analysis to unfold the relationship among the recorded variables and revealed three factors that accounted for 63% of the total variance. On Factor 1 variables measured in tugging with both the experimenter and owner had high loadings (labelled “Motivation for tugging”). Factor 2 contained all variables measuring fear and avoidance (Fear/Avoidance), and Factor 3 consisted of variables measured in ball game (Motivation for ball game). The cluster analysis of the dogs’ individual factor scores classified them into 5 significantly different groups on the basis of their tendency to be involved in playing with a ball, a rag and to show fear/avoidance during the tests. Moreover, the gender (but not the age or breed) of the dogs and the duration of the daily active interaction with the owner had significant effects on the distribution of dogs between the cluster groups. These results suggest that in play situations the behaviour of well socialized family dogs is influenced more by their motivation to play and to a certain extent by the level of fear than by the familiarity of the play partner or their possible general tendencies for cooperative or competitive behaviours. [Copyright &y& Elsevier]

In a spatially structured population, limited dispersal gives rise to local relatedness, potentially favoring indiscriminate helping behavior. However, it also leads to local competition, which reduces the benefits of helping local kin. This tension has become the focus for a growing body of theoretical work. Existing models, however, have focused chiefly on the net impact of limited dispersal on cooperative or competitive effort in a homogeneous population. Here, I extend existing models of kin selection in a group-structured population to allow for asymmetries in expected fecundity and reproductive success among group members. I explore the consequent impact of limited dispersal on the evolution of helping and harming behavior, and on the degree of reproductive inequality or skew. I show that when individuals in a group differ in their expected fecundity, limited dispersal gives rise to kin selection for harming behavior on the part of more fecund individuals, and for helping behavior on the part of less fecund individuals. As a result, philopatry tends to exaggerate differences in reproductive success, and so promotes greater reproductive skew. [ABSTRACT FROM AUTHOR]

Surveys of insect societies have revealed four key, recurring organizational trends: (i) The most elaborated cooperation occurs in groups of relatives. (ii) Cooperation is typically more elaborate in species with large colony sizes than in species with small colony sizes, the latter exhibiting greater internal reproductive conflict and lesser morphological and behavioral specialization. (iii) Within a species, per capita brood output typically declines as colony size increases. (iv). The ecological factors of resource patchiness and intergroup competition are associated with the most elaborated cooperation. Predictions of all four patterns emerge elegantly from a game-theoretic model in which within-group tug-of-wars are nested within a between-group tug-of-war. In this individual selection model, individuals are faced with the problem of how to partition their energy between investment in intercolony competition versus investment in intracolony competition, i.e., internal tugs-of-war over shares of the resources gained through intergroup competition. An individual's evolutionarily stable investment in between-group competition (i.e., within-group cooperation) versus within-group competition is shown to increase as within-group relatedness increases, to decrease as group size increases (for a fixed number of competing groups), to increase as the number of competing groups in a patch increases, and to decrease as between-group relatedness increases. Moreover, if increasing patch richness increases both the number of individuals within a group and the number of competing groups, greater overall cooperation within larger groups will be observed. The model presents a simple way of determining quantitatively how intergroup conflict will propel a society forward along a ‘superorganism continuum.’ [ABSTRACT FROM AUTHOR]

This study evaluated the effect of bite raising measurements produced by mouthguards (MG) on the exercise performance of athletes. Six baseball athletes (BA) and six tug-of-war athletes (TA) were selected as subjects. The MG for the BA were adjusted vertically for raising the bite by about 1.5, 2.5, and 3.5 mm respectively focusing on the molars. Physical activity was measured for both conditions with and without MG. Measurements were collected for the following physical activities : batter's swing speed(BSS), pitching speed (PS), and throwing distance (TD). MG for TA was adjusted vertically to raise the bite by about 5.0 and 7.0 mm, respectively focusing on the molars. The physical activity was measured for both conditions with and without MG. Measurements were collected for the following physical activities: grip strength (GS) and back strength (BS). The ratios (relative value) of the maximum values of each condition were calculated in comparison to the maximum value of the control group (those not using a MG). Spearman;s rank correlation coefficient was determined by comparing measurements of physical activity and bite raising measurements. Among BA, no correlation was found between TD, BSS and bite raising measurements. A weak correlation was found between PS and bite raising measurements. Among TA, a weak negative correlation between the GS and bite raising measurements was found. A positive correlation was found between the BS and bite raising measurements. These results suggest that there was less improvement in exercise performance for BA by bite raising use of a MG, and that it was possible to improve BS for TA. [ABSTRACT FROM AUTHOR]