Loser Effects Research Articles

The making of winners (and losers): how early dominance interactions determine adult social structure in a clonal fish.

Across a wide range of animal taxa, winners of previous fights are more likely to keep winning future contests, just as losers are more likely to keep losing. At present, such winner and loser effects are considered to be fairly transient. However, repeated experiences with winning and/or losing might increase the persistence of these effects, generating long-lasting consequences for social structure. To test this, we exposed genetically identical individuals of a clonal fish, the Amazon molly (Poecilia formosa), to repeated winning and/or losing dominance interactions during the first two months of their life. We subsequently investigated whether these experiences affected the fish's ability to achieve dominance in a hierarchy five months later after sexual maturity, a major life-history transition. Individuals that had only winning interactions early in life consistently ranked at the top of the hierarchy. Interestingly, individuals with only losing experience tended to achieve the middle dominance rank, whereas individuals with both winning and losing experiences generally ended up at the bottom of the hierarchy. In addition to demonstrating that early social interactions can have dramatic and long-lasting consequences for adult social behaviour and social structure, our work also shows that higher cumulative winning experience early in life can counterintuitively give rise to lower social rank later in life.

Short and long-lasting behavioral consequences of agonistic encounters between male Drosophila melanogaster

In many animal species, learning and memory have been found to play important roles in regulating intra- and interspecific behavioral interactions in varying environments. In such contexts, aggression is commonly used to obtain desired resources. Previous defeats or victories during aggressive interactions have been shown to influence the outcome of later contests, revealing loser and winner effects. In this study, we asked whether short- and/or long-term behavioral consequences accompany victories and defeats in dyadic pairings between male Drosophila melanogaster and how long those effects remain. The results demonstrated that single fights induced important behavioral changes in both combatants and resulted in the formation of short-term loser and winner effects. These decayed over several hours, with the duration depending on the level of familiarity of the opponents. Repeated defeats induced a long-lasting loser effect that was dependent on de novo protein synthesis, whereas repeated victories had no long-term behavioral consequences. This suggests that separate mechanisms govern the formation of loser and winner effects. These studies aim to lay a foundation for future investigations exploring the molecular mechanisms and circuitry underlying the nervous system changes induced by winning and losing bouts during agonistic encounters.

Losing reduces maximum bite performance in house cricket contests

Summary Whole‐organism performance capacities influence male combat outcomes in many animal species. However, several species also exhibit winner and loser effects, and current theory predicts that losers are more likely to lose again due to a decrease in aggression following defeat, not because of any change in underlying maximum performance capacity. To test the effect of fight experience on performance, we measured the maximum bite force of male Acheta domesticus crickets that were pitted against size‐matched opponents in staged fights. Winners then fought a second contest against other winners while losers fought other losers, after which we measured the change in bite force in all contest crickets and in a control group that did not take part in any contests. Bite force predicted fight outcomes in the first round, and losing the first fight had a significant effect on bite force, leading to a 20% decrease in relative bite force compared to crickets that won both rounds. However, winning did not increase performance as there was no difference between those that won the first round and those that never experienced a loss, nor did winning a second bout alleviate the negative effects on realized bite performance of losing an initial bout. Past defeats can therefore alter the realized short‐term maximal performance of traits that contribute to contest outcomes independent of maximum performance limits set by morphology.

Trustees, Delegates, and Responsiveness in Comparative Perspective

A large body of aggregate-level work shows that government policies do indeed respond to citizen preferences. But whether citizens recognize that government is responsive is another question entirely. Indeed, a prior question is whether or not citizens value responsiveness in the way that academic research assumes they should in the first place. Using comparative data from the European Social Survey, this article examines how citizens see government responsiveness. We show that several key assumptions of the aggregate-level literature are met at the individual level. But we also present results that show that attitudes toward representation and responsiveness are colored, sometimes in quite surprising ways, by winner–loser effects. In a finding that stands in some contrast to the normative literature on the topic, we show that these sorts of short-term attitudes help shape preferences for models of representation. In particular, we show that the distinction between delegates and trustees is a conceptual distinction that has limits in helping us to understand citizen preferences for representation.

Winner–loser effects in a eusocial wasp

What makes some individuals behaviorally more dominant than others? Although intrinsic factors such as body size and age have been well studied, extrinsic social factors like winner and loser effects have never before been addressed in eusocial species. Here we demonstrated the existence of both winner and loser effects in the primitively eusocial wasp, Ropalidia marginata. Such relative self-assessment and adjustment of fighting abilities may have significant implications for survival and fitness, and could be adaptive, especially in a social species where dominance encounters with conspecifics is the norm.

Self-organizing dominance hierarchies in a wild primate population.

Linear dominance hierarchies, which are common in social animals, can profoundly influence access to limited resources, reproductive opportunities and health. In spite of their importance, the mechanisms that govern the dynamics of such hierarchies remain unclear. Two hypotheses explain how linear hierarchies might emerge and change over time. The 'prior attributes hypothesis' posits that individual differences in fighting ability directly determine dominance ranks. By contrast, the 'social dynamics hypothesis' posits that dominance ranks emerge from social self-organization dynamics such as winner and loser effects. While the prior attributes hypothesis is well supported in the literature, current support for the social dynamics hypothesis is limited to experimental studies that artificially eliminate or minimize individual differences in fighting abilities. Here, we present the first evidence supporting the social dynamics hypothesis in a wild population. Specifically, we test for winner and loser effects on male hierarchy dynamics in wild baboons, using a novel statistical approach based on the Elo rating method for cardinal rank assignment, which enables the detection of winner and loser effects in uncontrolled group settings. Our results demonstrate (i) the presence of winner and loser effects, and (ii) that individual susceptibility to such effects may have a genetic basis. Taken together, our results show that both social self-organization dynamics and prior attributes can combine to influence hierarchy dynamics even when agonistic interactions are strongly influenced by differences in individual attributes. We hypothesize that, despite variation in individual attributes, winner and loser effects exist (i) because these effects could be particularly beneficial when fighting abilities in other group members change over time, and (ii) because the coevolution of prior attributes and winner and loser effects maintains a balance of both effects.

Sex differences in fighting-induced hyperaggression in a fly

In many animals, after experiencing an intraspecific aggressive interaction, winners are more likely to win again (the winner effect) and losers more likely to lose again (the loser effect). However, the winner and loser effect has been studied in few arthropod models, and comparative approaches between the sexes are hard to find. In this study, we evaluated the role of previous experience in male–male and female–female contests of Mediterranean fruit flies, Ceratitis capitata (Diptera: Tephritidae). In this species, lekking males fight for courtship territories, while females fight to maintain single oviposition sites, as well as for mates. We addressed the following questions. (1) Are winners more likely to win again and losers more likely to lose again? (2) Are different interfight intervals critical to detect experience-induced effects on aggression? (3) Are winning and losing probabilities affected solely by the outcome of the previous contests, or is fighting experience itself sufficient to induce the effect? (4) Does experience affect differently aggression displayed by males and females? Results showed reduced fighting success in males and females that experienced a single defeat, while individuals that experienced two previous victories or defeats had higher aggression rates and more wins in subsequent contests (i.e. hyperaggression). This was achieved merely by experiencing a contest, while the actual outcomes of previous fights did not affect the aggressiveness level. Some differences were documented between male–male and female–female contests (e.g. females fought longer than males), showing the value of a comparative approach between the sexes when studying experience-induced hyperaggression. This study highlights that both consecutive victories and defeats enhance fighting performances of fruit fly males and females defending courtship territories and oviposition sites, respectively. To the best of our knowledge, this is the first evidence about how repeated defeat experiences reverse the loser effect in animals, leading to higher fighting success.

Contest experience enhances aggressive behaviour in a fly: when losers learn to win.

In several animal species, aggressive experience influences the characteristics and outcomes of subsequent conflicts, such that winners are more likely to win again (the winner effect) and losers more likely to lose again (the loser effect). We tested the olive fruit fly, Bactrocera oleae (Diptera: Tephritidae), as a model system to evaluate the role of the winner and loser effects in male-male territorial contests. Further, we conducted experiments to test if winning and losing probabilities are affected only by the outcome of the previous contests, or whether the fighting experience itself is sufficient to induce an effect. Both winners and losers of two consecutive encounters displayed higher intensity of aggression and fought longer in subsequent contests. In both cases, they achieved higher fighting success than naïve males. The enhanced fighting performance of both winners and losers was stimulated by merely experiencing a contest, not necessarily by the relative outcome of previous fights. Overall, this study highlights the fact that previous victories and defeats both enhance aggressive behaviour in olive fruit flies, allowing them to achieve higher fighting success in subsequent contests against inexperienced males.

Modelling Dominance Hierarchies Under Winner and Loser Effects.

Animals that live in groups commonly form themselves into dominance hierarchies which are used to allocate important resources such as access to mating opportunities and food. In this paper, we develop a model of dominance hierarchy formation based upon the concept of winner and loser effects using a simulation-based model and consider the linearity of our hierarchy using existing and new statistical measures. Two models are analysed: when each individual in a group does not know the real ability of their opponents to win a fight and when they can estimate their opponents' ability every time they fight. This estimation may be accurate or fall within an error bound. For both models, we investigate if we can achieve hierarchy linearity, and if so, when it is established. We are particularly interested in the question of how many fights are necessary to establish a dominance hierarchy.

Winner and Loser Effects in Major League Baseball Double Headers

Across the animal kingdom it has been observed that outcomes of conflicts are influenced by past experiences, whereby previous winners are likely to keep winning and losers are likely to lose again. These so-called “winner and loser effects” are hypothesized to result from factors such as information acquisition and endocrine responses following the initial bouts. This paper applies the understanding of this phenomenon to a novel domain: patterns of winning and losing in Major League Baseball (MLB) double headers. By accessing archival data available from www.espn.com, we report on the incidence of a single team winning both games (sweeps) versus each team winning one game (splits) in MLB double headers over the last 13 years. Consistent with previous research on winner and loser effects, we show that sweeps are significantly more common than splits and that there is a home field advantage in this context. Results indicate that disparity in opponent quality or skill, as measured by the difference in team records outside the double header match, was not a significant predictor of whether the outcome resulted in a split or a sweep. In contrast to our hypotheses, there was no difference in the margin of victory in games between sweeps and splits. Overall these results add to the existing literature on winner and loser effects, provide a framework for pursuing further research in MLB, and suggest that winner and loser effects may be present across a variety of other forms of human social interaction.

Fighting experience alters brain androgen receptor expression dependent on testosterone status.

Contest decisions are influenced by the outcomes of recent fights (winner-loser effects). Steroid hormones and serotonin are closely associated with aggression and therefore probably also play important roles in mediating winner-loser effects. In mangrove rivulus fish, Kryptolebias marmoratus, individuals with higher testosterone (T), 11-ketotestosterone and cortisol levels are more capable of winning, but titres of these hormones do not directly mediate winner-loser effects. In this study, we investigated the effects of winning/losing experiences on brain expression levels of the receptor genes for androgen (AR), oestrogen α/β (ERα/β), glucocorticoid (GR) and serotonin (5-HT1AR). The effect of contest experience on AR gene expression depended on T levels: repeated losses decreased, whereas repeated wins increased AR gene expression in individuals with low T but not in individuals with medium or high T levels. These results lend strong support for AR being involved in mediating winner-loser effects, which, in previous studies, were more detectable in individuals with lower T. Furthermore, the expression levels of ERα/β, 5-HT1AR and GR genes were higher in individuals that initiated contests against larger opponents than in those that did not. Overall, contest experience, underlying endocrine state and hormone and serotonin receptor expression patterns interacted to modulate contest decisions jointly.

Losing the battle but winning the war: Uncertain outcomes reverse the usual effect of winning on testosterone

The biosocial model of status predicts a competition effect (or winner–loser effect), whereby winning a competition should cause a rise in testosterone relative to losing. However, its applicability to women and the role of contextual factors, such as a decisive versus close match, have been overlooked. In two studies of female competition, we tested whether the winner–loser effect generalizes to dominance contests that model unstable social hierarchies, namely in close competitions wherein the winner–loser distinction is unsettled (Study 1) and in competitions in which the outcome is uncertain (Study 2). In both studies we found evidence for a reverse winner–loser effect whereby losers experienced a net increase in testosterone compared to winners. Moreover, the rise in testosterone was stronger in those competitors who reported being more surprised by the loss (Study 2). These results represent some of the first empirical evidence for the reverse effect of what is predicted by the biosocial model of status. We interpret these findings in terms of the dominance motivation that testosterone might subserve within unstable status hierarchies.

Hermit crab, Pagurus middendorffii, males avoid the escalation of contests with familiar winners

Prior contest outcomes often affect subsequent contest behaviour (winner/loser effects). If contestants discriminate between familiar and unfamiliar opponents, individual recognition may alter the strength and/or manner of winner/loser effects. We examined whether hermit crabs, Pagurus middendorffii, changed their contest behaviour based on winner/loser effects, whether they distinguished a familiar opponent from an unfamiliar opponent, and how the familiarity with the opponent related to the winner/loser effects in male–male contests. Males of this species show precopulatory guarding behaviour, and male–male contests often occur between a guarding male and an intruder. In contests between unfamiliar males, intruders use self-assessment during the initial contact phase and mutual assessment during the physical combat phase to determine their behaviours. Precopulatory guarding males and females collected in the field were used in two consecutive trials of male–male contests. Losers in the first trial were used as focal intruders in the second trial with (1) a familiar opponent that had won the first trial, (2) an unfamiliar opponent that had won the first trial with another intruder, or (3) a naive opponent with no trial experience. Focal intruders did not alter their aggressiveness against either unfamiliar or naive opponents in the second trial. However, they rarely initiated physical combat against familiar opponents in the second trial. When they initiated combat, they gave up sooner against familiar opponents than against unfamiliar opponents. These results suggest that intruders are able to distinguish familiar opponents from others and decrease their aggressiveness only when they encounter familiar opponents. Our study therefore shows loser effects in P. middendorffii related to the familiarity with the opponent and suggests intruders can obtain information about their opponents during the initial encounter.

Duration of memory of dominance relationships in a group living cichlid.

Animal contests are costly and tend to escalate when rivals have similar competitive abilities. Individuals that remember dominance relationships with rivals may avoid repeated agonistic interactions and hence avoid the costs of repeated escalation of contests. However, it can be difficult to experimentally disentangle the effects of memory from those of loser effects (losers behaving subordinately due to prior defeats). Here, we test whether loser effects or individual memory mediate contest behaviour in the African cichlid, Julidochromis transcriptus. We find that on days 3 and 5 after initial contests, losers display subordinate behaviour to contest winners but not to novel contestants. However, this effect disappears after 7 days, at which time losers do not display subordinate behaviour to either rival. These results show that (1) this fish can recall a previously dominant contestant for up to 5 days and (2) as no subordinate displays were shown to the novel contestant, there are no evidences for loser effects in this species. Such short-term memory of past interactions may have broad significance in social species with repeated interactions.

Winning, losing, and reaching out

Here, we argue that behavioral ecologists can do even more than we have done to facilitate new, interdisciplinary collaborations. Our argument is a general one, but we focus on how to do this with winner and loser effects. We develop a new, general model of winner and loser effects as the outcome of flexible decisions about how much to invest in competition and discuss the model’s implications for overall levels of conflict within a species. Finally, we argue that winner and loser effects is a topic ripe for fostering collaborations with researchers in cultural anthropology and sports psychology. We would be rude and remiss if we did not start off with the appropriate salutation on an occasion such as this: Happy 25th anniversary, dear Behavioral Ecology! Perhaps it sounds overly emotional, but both of us love being behavioral ecologists, and we think Behavioral Ecology is a wonderful representative of our cherished discipline. The field of behavioral ecology, which seeks no less than to understand how ecology sets the stage on which natural selection acts on behavior, has grown by leaps and bounds since this journal was initiated. One of the many ways this has happened is by behavioral ecologists reaching out to those in related, and sometimes seemingly unrelated, disciplines—cognitive psychology, biological anthropology, mathematics, economics, and political science, to name just a few—and fostering collaborations, with the long-term goal of a deeper understanding of the roots of behavior. Not surprisingly, when such links are first established, each side can be reluctant to take the perspective of the other; but in time, openminded scientists, after heated discussions, sort through all that. We applaud this aggressive, interdisciplinary, collaborative approach and we try to take it ourselves—indeed, it is one of the many reasons we are behavioral ecologists. In this article, we simply want to make the case that behavioral ecologists can, and should, do even more to facilitate new, interdisciplinary collaborations. Our argument is a general one, but as a case in point, we focus on the winner and loser effects that behavioral ecologists have been studying from both proximate and ultimate perspectives, expand this work by developing a new, general model of winner and loser effects and their implications and argue that this topic is ripe for fostering collaborations with researchers in cultural anthropology and sports psychology. Winner and Loser e ffects and d ominance Hierarc H ies

Mechanisms of decision making during contests in green anole lizards: prior experience and assessment

Prior contest experiences can predictably alter an individual's contest performance and probability of contest success. Although winner and loser effects have been well studied across many animal taxa, the mechanisms underlying these effects and their adaptive value currently are topics of intense interest. Two predominant hypotheses posit that contest experiences alter either an individual's perceived fighting ability or its actual fighting ability. We addressed these hypotheses, and potential physiological and behavioural mechanisms driving experience effects in the green anole lizard, Anolis carolinensis. Prior losers went on to lose a significant proportion of future contests while prior winners were equally likely to win or lose against size-matched opponents. Further analysis revealed that the loser effect arose as a result of individuals updating their perceived fighting ability following a loss. Both prior losing and winning experiences influenced future contest performance with prior losers decreasing and prior winners increasing their aggressiveness in subsequent contests. Status-dependent changes in metabolic physiology were not associated with the presence of the observed loser effect. However, contest status and contest performance interacted to influence metabolic physiology. Plasma glucose concentrations decreased as a function of the frequency of high-risk, escalated behaviours performed by eventual losers, and muscle lactate concentrations increased as a function of the frequency of low-risk threat displays performed by eventual winners. Our results support the notion that prior contest experiences influence an individual's perceived, not actual, fighting ability and that status-dependent changes in metabolic physiology are not a likely mechanism underlying the presence/magnitude of experience effects.

The Trophy Effect

ABSTRACTBy extending a typical endowment effect experiment with the possibility of winning the endowment in a real effort contest, we found two reinforcing effects that led to a complete market failure. Subjects who won the item in the effortful competition had a very high willingness to accept (trophy winner effect). By contrast, subjects who were not successful had an extremely low willingness to pay for the same item (trophy loser effect). We disentangle different components of these effects and investigate the underlying emotional responses. Further, we analyze the duration of the effects and discuss economic implications. Copyright © 2013 John Wiley & Sons, Ltd.

Juvenile social experience affects pairing success at adulthood: congruence with the loser effect?

Social interactions with adults are often critical for the development of mating behaviours. However, the potential role of other primary social partners such as juvenile counterparts is rarely considered. Most interestingly, it is not known whether interactions with juvenile females improve males' courtship and whether, similar to the winner and loser effects in a fighting context--outcome of these interactions shapes males' behaviour in future encounters. We investigated the combined effects of male quality and juvenile social experience on pairing success at adulthood in zebra finches (Taeniopygia guttata). We manipulated brood size to alter male quality and then placed males in either same- or mixed-sex juvenile dyads until adulthood. We found that males from reduced broods obtained more copulations and males from mixed-sex dyads had more complete courtships. Furthermore, independent of their quality, males that failed to pair with juvenile females, but not juvenile males, had a lower pairing success at adulthood. Our study shows that negative social experience with peers during adolescence may be a potent determinant of pairing success that can override the effects of early environmental conditions on male attractiveness and thereby supports the occurrence of an analogous process to the loser effect in a mating context.

Aminergic Control of Social Status in Crayfish Agonistic Encounters

Using pairings of male crayfish Procambarus clarkii with a 3–7% difference in size, we confirmed that physically larger crayfish were more likely to win encounters (winning probability of over 80%). Despite a physical disadvantage, small winners of the first pairings were more likely to win their subsequent conflicts with larger naive animals (winning probability was about 70%). By contrast, the losers of the first pairings rarely won their subsequent conflicts with smaller naive animals (winning probability of 6%). These winner and loser effects were mimicked by injection of serotonin and octopamine. Serotonin-injected naive small crayfish were more likely to win in pairings with untreated larger naive crayfish (winning probability of over 60%), while octopamine-injected naive large animals were beaten by untreated smaller naive animals (winning probability of 20%). Furthermore, the winner effects of dominant crayfish were cancelled by the injection of mianserin, an antagonist of serotonin receptors and were reinforced by the injection of fluoxetin, serotonin reuptake inhibitor, just after the establishment of social order of the first pairings. Injection of octopamine channel blockers, phentolamine and epinastine, by contrast, cancelled the loser effects. These results strongly suggested that serotonin and octopamine were responsible for winner and loser effects, respectively.

Isolation Associated Aggression – A Consequence of Recovery from Defeat in a Territorial Animal

Population density has profound influences on the physiology and behaviour of many animal species. Social isolation is generally reported to lead to increased aggressiveness, while grouping lowers it. We evaluated the effects of varying degrees of isolation and grouping on aggression in a territorial insect, the Mediterranean field cricket, Gryllus bimaculatus . Substantiating early observations, we show that dyadic contests between weight-matched, adult male crickets taken from groups rarely escalate beyond threat displays, whereas interactions between pairs of previously isolated crickets typically escalate to physical fights lasting several seconds. No significant differences were found between 1, 2 and 6-day isolates, or between individuals grouped for a few hours or lifelong. Unexpectedly, crickets grouped in immediate proximity within individual mesh cages that precluded fighting while permitting visual, olfactory and mechanical, antennal contact, were as aggressive as free isolates. This suggests that reduced aggression of grouped animals may be an acquired result of fighting. Supporting this notion, isolated crickets initially engage in vigorous fights when first grouped, but fighting intensity and duration rapidly decline to the level of life-long grouped crickets within only 10 min. Furthermore, grouped crickets become as aggressive as life-long isolates after only 3 hours of isolation, and on the same time course required for crickets to regain their aggressiveness after social defeat. We conclude that the reduced aggressiveness of grouped crickets is a manifestation of the loser effect resulting from social subjugation, while isolation allows recovery to a state of heightened aggressiveness, which in crickets can be considered as the default condition. Given the widespread occurrence of the loser effect in the Animal Kingdom, many effects generally attributed to social isolation are likely to be a consequence of recovery from social subjugation.