Facial width-to-height ratio in a Turkish population is not sexually dimorphic and is unrelated to aggressive behavior

Recently, Weston et al. (2004; Wide faces or large canines? The attractive versus the aggressive primate. Proceedings of the Royal Society of London, Series B, 271, 416–419) found that facial width-to-height ratio (WHR) is a sexually dimorphic characteristic in humans; males have higher facial WHR than females. Following this study, Carré et al. (2008; In your face: facial metrics predict aggressive behavior in the laboratory and in varsity and professional hockey players. Proceedings of the Royal Society of London, Series B, 275, 2651–2656) found that individual differences in facial WHR accounted for a significant proportion of the variance in aggressive behavior of men, but not women. I tested these two hypotheses in a sample of 470 Turkish university students. Facial WHR was measured from frontal photographs. I also measured the aggressiveness level of 212 individuals using the Buss and Perry aggressiveness questionnaire. The mean facial WHR (and standard deviation) was 1.89±0.12 for males and 1.91±0.11 for females. There was no relationship between facial WHR and the self-reported aggressive behavior for either sex. The facial WHR is not a sexually dimorphic characteristic (at least) for Turkish people, and it does not appear to be associated with self-reported trait aggression.     

Male facial width is associated with death by contact violence: narrow-faced males are more likely to die from contact violence

Male facial width-to-height ratio (bizygomatic width scaled for face height) is a testosterone-linked trait predictive of reactive aggression, exploitative behavior, cheating, deception, and dominance. We tested whether facial width was systematically related to cause of death in a forensic sample. We hypothesized that wider-faced males, being more aggressive and robust, would be less likely than narrower-faced males to die from contact violence (stabbed, strangled, or bludgeoned to death) compared with other forms of homicide. We tested this hypothesis in a forensic data sample covering 523 male and 339 female skeletons. In these data, men with narrower faces were more likely to have died as a consequence of homicides involving direct physical contact than men with wider faces. No such effect was found for women. This effect was found when considering all causes of mortality and when limiting the sample to homicides. This finding suggests that wider-faced males are less likely to die from male–male physical violence, perhaps because of their formidability. Our findings are discussed with reference to the previous literature indicating that facial width-to-height ratio is a marker for male dominance.     

Facial width-to-height ratio predicts self-reported dominance and aggression in males and females,but a measure of masculinity does not

Recently, associations between facial structure and aggressive behaviour have been reported. Specifically, the facial width-to-height ratio (fWHR) is thought to link to aggression, although it is unclear whether this association is related to a specific dimension of aggression, or to a more generalized concept of dominance behaviour. Similarly, an association has been proposed between facial masculinity and dominant and aggressive behaviour, but, to date, this has not been formally tested. Because masculinity and fWHR are negatively correlated, it is unlikely that both signal similar behaviours. Here, we thus tested these associations and show that: (i) fWHR is related to both self-reported dominance and aggression; (ii) physical aggression, verbal aggression and anger, but not hostility are associated with fWHR; (iii) there is no evidence for a sex difference in associations between fWHR and aggression; and (iv) the facial masculinity index does not predict dominance or aggression. Taken together, these results indicate that fWHR, but not a measure of facial masculinity, cues dominance and specific types of aggression in both sexes.     

Detection of Propensity for Aggression based on Facial Structure Irrespective of Face Race

The human face provides a wealth of information pertaining to the internal state and life-stage history of an individual. Facial width-to-height ratio is a size-independent sexually dimorphic trait, and estimates of aggression made by untrained adults judging own-race faces were positively associated with both facial width-to-height ratio and actual aggressive behavior. Given the significant adaptive value of accurately detecting aggressiveness based on facial appearance, we hypothesized that aggression estimates made by adults and 8-year-olds would be highly correlated with male facial width-to-height ratio even for a face category with which they had minimal experience-other-race faces. For each of the four race and age groups, estimates of aggression were positively correlated with facial width-to-height ratio irrespective of rating own-or other-race faces. Overall, the correlations between facial width-to-height ratio and ratings of aggression were stronger for adults than for children. Sensitivity to facial width-to-height ratio appears to be part of an evolved mechanism designed to detect threats in the external environment. This mechanism is likely broadly tuned and functions independently of experience.     

A Lack of Sexual Dimorphism in Width-to-Height Ratio in White European Faces Using 2D Photographs, 3D Scans, and Anthropometry

Facial width-to-height ratio has received a great deal of attention in recent research. Evidence from human skulls suggests that males have a larger relative facial width than females, and that this sexual dimorphism is an honest signal of masculinity, aggression, and related traits. However, evidence that this measure is sexually dimorphic in faces, rather than skulls, is surprisingly weak. We therefore investigated facial width-to-height ratio in three White European samples using three different methods of measurement: 2D photographs, 3D scans, and anthropometry. By measuring the same individuals with multiple methods, we demonstrated high agreement across all measures. However, we found no evidence of sexual dimorphism in the face. In our third study, we also found a link between facial width-to-height ratio and body mass index for both males and females, although this relationship did not account for the lack of dimorphism in our sample. While we showed sufficient power to detect differences between male and female width-to-height ratio, our results failed to support the general hypothesis of sexual dimorphism in the face.     

Sex-Specific Aggression and Antipredator Behaviour in Young Brown Trout

Sex differences in adult behaviour are often interpreted as consequences of sexual selection and/or different reproductive roles in males and females. Sex-specific juvenile behaviour, however, has received less attention. Adult brown trout males are more aggressive than females during spawning and juvenile aggression may be genetically correlated with adult aggression in fish. We therefore tested the prediction that immature brown trout males are more aggressive and bolder than immature females. Because previous work has suggested that precocious maturation increases dominance in salmonids, we included precocious males in the study to test the prediction that early sexual maturation increase male aggression and boldness. Aggression and dominance relations were estimated in dyadic contests, whereas boldness was measured as a response to simulated predation risk using a model heron. Independent of maturity state, males initiated more than twice as many agonistic interactions as females in intersexual contests. However, males were not significantly more likely to win these contests than females. The response to a first predator attack did not differ between sex categories, but males reacted less to a second predator attack than females. Sexual maturity did not affect the antipredator response in males. Since there is no evidence from field studies that stream-living immature male and female salmonids differ in growth rate, it appears unlikely that the sex differences demonstrated are behavioural consequences of sex-specific investment in growth. It seems more likely that sex-specific behaviour arises as a correlated response to sexually selected gene actions promoting differential behaviour in adult males and females during reproduction. Alternatively, sex differences may develop gradually during juvenile life, because a gradual developmental program should be less costly than a sudden behavioural change at the onset of sexual maturity.     

Aggression in young men high in threat potential increases after hearing low-pitched male voices: two tests of the retaliation-cost model

Research suggests that male voice pitch is an honest dominance signal because it indexes men's physicality and because lower-pitched voices are more costly to develop and maintain. Rather than considering these signaler-dependent mechanisms, we tested a receiver-dependent mechanism hypothesized by M. Enquist's (1985) retaliation-cost model of aggressive signaling. The model predicts that, given a competitive scenario, low-pitched male voices will elicit aggression from male listeners (i.e., signal receivers) who are relatively high in threat potential. We confirmed this hypothesis in two experiments. Under a sexual but not control prime and after listening to low- but not average-pitched male voices, increases in heterosexual male participants' trait dominance predicted stronger aggressive cognitions (Experiment 1), and increases in male participants' handgrip strength predicted stronger aggressive intent (Experiment 2). These findings provide the first direct support for the retaliation-cost model in humans, extend research on the effects of male voice pitch on receiver psychology, and demonstrate an additional cost mechanism that explains why voice pitch is an honest signal of dominance in men.     

Physiological correlates of skating performance in women's and men's ice hockey

The purpose of the current investigation was to identify relationships between physiological off-ice tests and on-ice performance in female and male ice hockey players on a comparable competitive level. Eleven women, 24 ± 3.0 years, and 10 male ice hockey players, 23 ± 2.4 years, were tested for background variables: height, body weight (BW), ice hockey history, and lean body mass (LBM) and peak torque (PT) of the thigh muscles, VO2peak and aerobic performance (Onset of Blood Lactate Accumulation [OBLA], respiratory exchange ratio [RER1]) during an incremental bicycle ergometer test. Four different on-ice tests were used to measure ice skating performance. For women, skating time was positively correlated (p < 0.05) to BW and negatively correlated to LBM%, PT/BW, OBLA, RER 1, and VO2peak (ml O2·kg(-1) BW(-1)·min(-1)) in the Speed test. Acceleration test was positively correlated to BW and negatively correlated to OBLA and RER 1. For men, correlation analysis revealed only 1 significant correlation where skating time was positively correlated to VO2peak (L O2·min(-1)) in the Acceleration test. The male group had significantly higher physiological test values in all variables (absolute and relative to BW) but not in relation to LBM. Selected off-ice tests predict skating performance for women but not for men. The group of women was significantly smaller and had a lower physiological performance than the group of men and were slower in the on-ice performance tests. However, gender differences in off-ice variables were reduced or disappeared when values were related to LBM, indicating a similar capacity of producing strength and aerobic power in female and male hockey players. Skating performance in female hockey players may be improved by increasing thigh muscle strength, oxygen uptake, and relative muscle mass.     

Effectiveness of interventions to reduce aggression and injuries among ice hockey players: a systematic review

Background:

The increasing incidence of injuries related to playing ice hockey is an important public health issue. We conducted a systematic review to evaluate the effectiveness of interventions designed to reduce injuries related to aggressive acts in ice hockey.

Methods:

We identified relevant articles by searching electronic databases from their inception through July 2012, by using Internet search engines, and by manually searching sports medicine journals, the book series Safety in Ice Hockey and reference lists of included articles. We included studies that evaluated interventions to reduce aggression-related injuries and reported ratings of aggressive behaviour or rates of penalties or injuries.

Results:

We identified 18 eligible studies. Most involved players in minor hockey leagues. Of 13 studies that evaluated changes in mandatory rules intended to lessen aggression (most commonly the restriction of body-checking), 11 observed a reduction in penalty or injury rates associated with rule changes, and 9 of these showed a statistically significant decrease. The mean number of penalties decreased by 1.2–5.9 per game, and injury rates decreased 3- to 12-fold. All 3 studies of educational interventions showed a reduction in penalty rates, but they were not powered or designed to show a change in injury rates. In 2 studies of cognitive behavioural interventions, reductions in aggressive behaviours were observed.

Interpretation:

Changes to mandatory rules were associated with reductions in penalties for aggressive acts and in injuries related to aggression among ice hockey players. Effects of educational and cognitive behavioural interventions on injury rates are less clear. Well-designed studies of multifaceted strategies that combine such approaches are required.Over the last 15 years, the incidence of brain and spinal cord injuries among ice hockey players has increased.¹ A recent study involving players in junior leagues found that, in the 2009/10 hockey season, the incidence of game-related concussions was 7 times higher than the highest rate previously reported in 1998/99.² Brain injuries frequently result from aggressive bodychecking³ and account for 15% of injuries among players 9–16 years of age.^4,5 In a study of a community-based hockey program involving boys aged 9–15 years, hostile aggressive acts, which have an intention to do harm,⁶ were the primary cause of injury in one-third of games in which an injury resulted.⁷ Among high school students in Minnesota who played varsity ice hockey, those who played to relieve aggression were 4 times more likely than other players to experience a concussion.⁸ These findings highlight the association between aggressive behaviour and injury in ice hockey. However, little is known about what can be done to reduce this behaviour to create a safer environment for the sport.Existing reviews about reducing injury in sport have primarily assessed equipment or risk factors associated with injury.^9–11 Recent systematic reviews highlighted the risks of bodychecking and renewed calls for policies to disallow bodychecking among youth playing ice hockey.^3,12 We conducted a systematic review to assess the effectiveness of interventions designed to reduce aggressive acts and related injuries among ice hockey players. We were particularly interested in evaluating the effectiveness of rule changes, educational interventions and behavioural modification in reducing aggressive acts and related injuries.     

Dominance,Age and Aggression among Female Pronghorn,Antilocapra americana (Family: Antilocapridae)

The relationships among dominance, age and aggressive behaviour of marked, female pronghorn (Antilocapra americana; Family Antilocapridae) were studied in north central Colorado. Females formed dominance hierarchies with few circular relationships. Unlike other female ungulates, dominance rank was not correlated with age. Dominance rank was negatively correlated with rate of aggression initiated in summer and winter; however, aggressiveness as an individual trait was not related to dominance. Older females received higher rates of aggression than younger females in summer and winter. During the rut, dominance rank was correlated with rate of aggression received but not with rate of aggression initiated. Patterns of aggression that differ by season within a given hierarchy of dominance relationships suggest a different cause or function of aggressive behaviour in different seasons.     

Gender differences in hockey players during on-ice graded exercise

The purpose of this study was to examine whether gender differences exist for ventilatory threshold (VT), lactate threshold (LT), and Vo2max during on-ice skating in college hockey players. Ten male and 10 female Division III college hockey players performed a graded exercise skating protocol until reaching volitional fatigue. The graded exercise test employed stages that were 80 seconds in duration, with 40 seconds of rest between each stage to obtain blood lactate samples. Ventilatory threshold occurred at a higher percentage of maximal heart rate (HRmax) in women than in men. The women's VT occurred at 77.3% +/- 1.6% HRmax, while the men's VT occurred at 72.6% +/- 2.0% HRmax (p < 0.02). Men and women had similar HRmax values: 191.3 +/- 2.5 b.min and 185.8 +/- 2.5 b.min, respectively. Vo2max was different between genders, with men at 52.7 +/- 1.3 mL.kg.min and women at 40.1 +/- 1.0 mL.kg.min (p < 0.01). In addition, VT was different between genders when measured as a percentage of Vo2max, with men at 52.7% +/- 3.2% and women at 67.3% +/- 4.0% (p < 0.02). In contrast, LT was similar between genders when expressed as a percentage of HRmax or Vo2max. For each gender, LT occurred at a significantly higher percentage of HRmax or Vo2max than VT did. It can be concluded that VT does not accurately predict LT in male or female hockey players. Additionally, competitive female hockey players have a lower Vo2max but a higher VT than their male counterparts. An increased VT may be a compensatory mechanism to offset the smaller Vo2max values measured in female hockey players. On-ice testing is a practical way to address specific aerobic training needs of hockey players.     

Prediction of reduction in aggressive behaviour of growing pigs using skin lesion traits as selection criteria

Aggression at regrouping is a common issue in pig farming. Skin lesions are genetically and phenotypically correlated with aggression and have been shown to have a significant heritable component. This study predicts the magnitude of reduction in complex aggressive behavioural traits when using lesion numbers on different body regions at two different time points as selection criteria, to identify the optimum skin lesion trait for selection purposes. In total, 1146 pigs were mixed into new social groups, and skin lesions were counted 24 h (SL24h) and 3 weeks (SL3wk) post-mixing, on the anterior, centre and posterior regions of the body. An animal model was used to estimate genetic parameters for skin lesion traits and 14 aggressive behavioural traits. Estimated breeding values (EBVs) and phenotypic values were scaled and standardised to allow direct comparison across multiple traits. Individuals with SL24h and SL3wk EBVs in the least aggressive 10% of the population were compared with the population mean to predict the expected genetic and phenotypic response in aggressive behaviour to selection. At mixing, selection for low anterior lesions was predicted to affect substantially more behavioural traits of aggressiveness than lesions obtained on other body parts, with EBVs between −0.21 and −1.17 SD below the population mean. Individuals with low central SL24h EBVs also had low EBVs for aggressive traits (−0.33 to −0.55). Individuals with high SL3wk EBVs had low EBVs for aggression at mixing (between −0.24 and −0.53 SD below the population mean), although this was predicted to affect fewer traits than selection against SL24h. These results suggest that selection against anterior SL24h would result in the greatest genetic and phenotypic reduction in aggressive behaviour recorded at mixing. Selection for increased SL3wk was predicted to reduce aggression at mixing; however, current understanding about aggressive behaviour under stable social conditions is insufficient to recommend using this trait for selection purposes.     

Lack of Support for the Association between Facial Shape and Aggression: A Reappraisal Based on a Worldwide Population Genetics Perspective

Antisocial and criminal behaviors are multifactorial traits whose interpretation relies on multiple disciplines. Since these interpretations may have social, moral and legal implications, a constant review of the evidence is necessary before any scientific claim is considered as truth. A recent study proposed that men with wider faces relative to facial height (fWHR) are more likely to develop unethical behaviour mediated by a psychological sense of power. This research was based on reports suggesting that sexual dimorphism and selection would be responsible for a correlation between fWHR and aggression. Here we show that 4,960 individuals from 94 modern human populations belonging to a vast array of genetic and cultural contexts do not display significant amounts of fWHR sexual dimorphism. Further analyses using populations with associated ethnographical records as well as samples of male prisoners of the Mexico City Federal Penitentiary condemned by crimes of variable level of inter-personal aggression (homicide, robbery, and minor faults) did not show significant evidence, suggesting that populations/individuals with higher levels of bellicosity, aggressive behaviour, or power-mediated behaviour display greater fWHR. Finally, a regression analysis of fWHR on individual''s fitness showed no significant correlation between this facial trait and reproductive success. Overall, our results suggest that facial attributes are poor predictors of aggressive behaviour, or at least, that sexual selection was weak enough to leave a signal on patterns of between- and within-sex and population facial variation.     

Individual differences affect honest signalling in a songbird

Research in the past decade has established the existence of consistent individual differences or ‘personality’ in animals and their important role in many aspects of animal behaviour. At the same time, research on honest signalling of aggression has revealed that while some of the putative aggression signals are reliable, they are only imperfectly so. This study asks whether a significant portion of the variance in the aggression-signal regression may be explained by individual differences in signalling strategies. Using the well-studied aggressive signalling system of song sparrows (Melospiza melodia), we carried out repeated assays to measure both aggressive behaviours and aggressive signalling of territorial males. Through these assays, we found that aggressive behaviours and aggressive signalling were both highly repeatable, and moreover that aggressive behaviours in 2009–2010 predicted whether the birds would attack a taxidermic mount over a year later. Most significantly, we found that residual variation in signalling behaviours, after controlling for aggressive behaviour, was individually consistent, suggesting there may be a second personality trait determining the level of aggressive signalling. We term this potential personality trait ‘communicativeness’ and discuss these results in the context of honest signalling theories and recent findings reporting prevalence of ‘under-signalling’.     

Facing aggression: cues differ for female versus male faces

The facial width-to-height ratio (face ratio), is a sexually dimorphic metric associated with actual aggression in men and with observers'' judgements of aggression in male faces. Here, we sought to determine if observers'' judgements of aggression were associated with the face ratio in female faces. In three studies, participants rated photographs of female and male faces on aggression, femininity, masculinity, attractiveness, and nurturing. In Studies 1 and 2, for female and male faces, judgements of aggression were associated with the face ratio even when other cues in the face related to masculinity were controlled statistically. Nevertheless, correlations between the face ratio and judgements of aggression were smaller for female than for male faces (F_1,36 = 7.43, p = 0.01). In Study 1, there was no significant relationship between judgements of femininity and of aggression in female faces. In Study 2, the association between judgements of masculinity and aggression was weaker in female faces than for male faces in Study 1. The weaker association in female faces may be because aggression and masculinity are stereotypically male traits. Thus, in Study 3, observers rated faces on nurturing (a stereotypically female trait) and on femininity. Judgements of nurturing were associated with femininity (positively) and masculinity (negatively) ratings in both female and male faces. In summary, the perception of aggression differs in female versus male faces. The sex difference was not simply because aggression is a gendered construct; the relationships between masculinity/femininity and nurturing were similar for male and female faces even though nurturing is also a gendered construct. Masculinity and femininity ratings are not associated with aggression ratings nor with the face ratio for female faces. In contrast, all four variables are highly inter-correlated in male faces, likely because these cues in male faces serve as “honest signals”.     

Is sociopolitical egalitarianism related to bodily and facial formidability in men?

Social bargaining models predict that men should calibrate their egalitarian attitudes to their formidability and/or attractiveness. A simple social bargaining model predicts a direct negative association between formidability/attractiveness and egalitarianism, whereas a more complex model predicts an association moderated by wealth. Our study tested both models with 171 men, using two sociopolitical egalitarianism measures: social dominance orientation and support for redistribution. Predictors included bodily formidability and attractiveness and four facial measures (attractiveness, dominance, masculinity, and width-to-height ratio). We also controlled for time spent lifting weights, and experimentally manipulated self-perceived formidability in an attempt to influence egalitarianism. Both the simple and complex social bargaining models received partial support: sociopolitical egalitarianism was negatively related to bodily formidability, but unrelated to other measures of bodily/facial formidability/attractiveness; and a formidability-wealth interaction did predict variance in support for redistribution, but the nature of this interaction differed somewhat from that reported in previous research. Results of the experimental manipulation suggested that egalitarianism is unaffected by self-perceived formidability in the immediate short-term. In sum, results provided some support for both the simple and complex social bargaining models, but suggested that further research is needed to explain why male formidability/attractiveness and egalitarianism are so often negatively related.     

Telling facial metrics: facial width is associated with testosterone levels in men

High facial width-to-height ratio (fWHR) has been associated with a cluster of behavioural traits in men, including aggression and status-striving. This association between face structure and behaviour may be caused by testosterone. Here we investigated the relationship of both baseline and reactive testosterone levels to fWHR. In addition, we investigated the link between testosterone and three well-characterised sexually dimorphic facial metrics. Testosterone was measured in one sample of males (n = 185) before and after a speed-dating event. An additional sample provided only baseline testosterone measures (n = 92). fWHR was positively associated with testosterone reactions to potential mate exposure and marginally associated with baseline testosterone in Sample 1. We found a positive association with baseline testosterone and fWHR in Sample 2. In addition, face-width-to-lower-height ratio was positively associated with testosterone in both samples, suggesting that, in particular, facial width (scaled by two measures of facial height) is associated with testosterone. Importantly, our results also indicate that there is no association between adult testosterone and the sexual dimorphism of face shape. Thus, while our findings question the status of sexual dimorphism as a proxy measure of testosterone, they do provide evidence that testosterone is linked to fWHR and might underlie the relationship between fWHR and behaviour.     

Men’s Facial Width-to-Height Ratio Predicts Aggression: A Meta-Analysis

Recent research has identified men’s facial width-to-height ratio (fWHR) as a reliable predictor of aggressive tendencies and behavior. Other research, however, has failed to replicate the fWHR-aggression relationship and has questioned whether previous findings are robust. In the current paper, we synthesize existing work by conducting a meta-analysis to estimate whether and how fWHR predicts aggression. Our results indicate a small, but significant, positive relationship between men’s fWHR and aggression.     

Effects of previous experience on the agonistic behaviour of male crickets, Gryllus bimaculatus

Male solitary animals frequently enter aggressive interactions with conspecific individuals to protect their territory or to gain access to females. After an agonistic encounter, the loser (subordinate individual) changes its behaviour from aggression to avoidance. We investigated agonistic interactions between pairs of male crickets to understand how dominance is established and maintained. Two na?ve males readily entered into agonistic interactions. Fights escalated in a stereotyped manner and were concluded with the establishment of dominance. If individuals were isolated after the first encounter and placed together 15 minutes later, subordinate crickets tended to avoid any further contact with the former dominant opponent. Moreover, subordinate males also avoided unfamiliar dominant and na?ve opponents. They displayed aggressive behaviour only towards unfamiliar subordinate opponents. This suggests that the subordinate male change their behaviour depending on the dominance status of the opponent. Dominant crickets, in contrast, displayed aggressive behaviour towards familiar as well as unfamiliar opponents. If the interval between the first and second encounter was longer than 30 minutes, the former subordinate male showed aggressive behaviour again. However, if the subordinate cricket was paired with the same opponent three consecutive times within 45 minutes, it avoided the former dominant opponent for up to 6 hours following the third encounter. Our results suggest that the maintenance of dominance in male crickets depends largely on the behavioural change of subordinate individuals. Possible mechanisms to maintain dominance are discussed.     

Patterns of Aggression and Operational Sex Ratio Within Alternative Male Phenotypes in Atlantic Salmon

The intensity of male–male aggression during mating is predicted to increase with the operational sex ratio (OSR) (the ratio of sexually active males to females). We observed aggressive behaviour in relation to OSR within alternative phenotypes (large anadromous males and small ‘sneaker’ mature male parr) of Atlantic salmon, Salmo salar, as they competed for access to anadromous females in large outdoor arenas immediately prior to spawning events as well as throughout the spawning season. Anadromous males were primarily aggressive outside of spawning events, and their aggression increased with OSR over a narrow range of 0.08–4. By contrast, mature male parr were aggressive just prior to spawning, with a decrease in aggression over a broad range of OSRs from 1 to 7.4. Similarly, literature data for three other salmonid species indicated a decrease in aggression with increasing OSRs over a range of 1–6.33. These observations suggest that there is considerable variability in competitive behaviour, even within alternative phenotypes. Because our data are derived from repeated observations on the same individuals of different genetic origin, further confirmation of these findings is desirable. Nevertheless, our study underscores the importance of measuring competitive behaviour and OSR at ecologically relevant spatial and temporal scales, both of which may differ between alternative maturation phenotypes.