Play Fighting Research Articles

Responding to inequities: gorillas try to maintain their competitive advantage during play fights

Humans respond to unfair situations in various ways. Experimental research has revealed that non-human species also respond to unequal situations in the form of inequity aversions when they have the disadvantage. The current study focused on play fights in gorillas to explore for the first time, to our knowledge, if/how non-human species respond to inequities in natural social settings. Hitting causes a naturally occurring inequity among individuals and here it was specifically assessed how the hitters and their partners engaged in play chases that followed the hitting. The results of this work showed that the hitters significantly more often moved first to run away immediately after the encounter than their partners. These findings provide evidence that non-human species respond to inequities by trying to maintain their competitive advantages. We conclude that non-human primates, like humans, may show different responses to inequities and that they may modify them depending on if they have the advantage or the disadvantage.

Play fighting and corticotropin-releasing hormone in the lateral septum of golden hamsters

This study was focused on determining the possible role of corticotropin-releasing hormone (CRH) on play fighting in juvenile golden hamsters. As no specific neural sites have been proposed, we looked for changes in CRH innervations at the peak of play-fighting activity on postnatal day 35 (P-35) from a week before on P-28. We noted that the increase in play-fighting activity between these two dates was associated with a 100% increase of the density of CRH fibers within the lateral septum. We, then, tested the possible role of CRH receptors on play fighting within the lateral septum through microinjections of α-helical CRH, a CRH receptor antagonist (either 0, 30, or 300 ng), directly into the area. The treatments inhibited play-fighting attacks and pins as well as reduced the duration of time that the resident hamsters spent in contact with the intruders, though locomotor activity remained unaffected. The possible source of CRH release in the lateral septum was addressed by quantification of CRH neurons also labeled with a marker of cellular activity, c-Fos, after consummation of play fighting. CRH neurons in the horizontal part of the diagonal band, an area reciprocally connected with the lateral septum, showed a 75% increase in double labeling with c-Fos as compared to controls. Together, these data show that CRH receptors in the lateral septum have a general role on play fighting, not just facilitating its consummation, but also likely enhancing appetitive aspects as well. In addition, this effect is associated with enhanced CRH availability in the area and enhanced neuronal activity within interconnected areas.

Targets and Tactics of Play Fighting: Competitive versus Cooperative Styles of Play in Japanese and Tonkean Macaques

Macaques are the most geographically widespread and behaviorally diverse primate genus, and although macaque species share the same, basic social structure, they display broad inter specificvariation in patterns of adult social behavior. Based on these patterns, macaque species have been arranged along a 4-grade scale for social style. At one end of the scale, there are grade 1 species (e.g., Japanese macaques) that have highly hierarchical and despotic social systems, and at the other end, grade 4 species (e.g., Tonkean macaques) that have more relaxed and egalitarian social systems. We predicted that a species from the more despotic end of the spectrum should have more competitive play fights and that a species from the egalitarian end, more cooperative ones. A detailed analysis of videotaped sequences of juvenile play fighting in Tonkean and Japanese macaques was used to characterize the targets and tactics of attack and defense. Even though the two species have a similar behavioral repertoire, there are significant differences in how that repertoire is used and these differences are consistent with one species having more competitive interactions than the other. Contrasting multi-animal play fights versus pairs showed that the more cooperative style of the Tonkean macaques is further exaggerated. The results suggest that differences in styles of attack anddefense in play fighting may be influenced by differences in the species’ social systems.

Violent Video Games Prime Both Aggressive and Positive Cognitions

Previous studies have shown that violent video games prime aggressive thoughts and concepts. Interestingly, positively valenced test stimuli are rarely used in this field, though they might provide useful information on the nature of the emotional response to virtual violence and its associative structure. According to the General Aggression Model (GAM) and its extensions ( Carnagey, Anderson, & Bushman, 2007 ), normal negative reactions to violence are expected. Alternatively, playing violent video games might be construed as engaging in positively valenced playful fighting behavior. To test the potential of violent video games to prime positive concepts, N = 29 adult males played either a violent or a nonviolent video game for 20 minutes and were subsequently tested in a standard lexical decision task consisting of positive, aggressive, nonaggressive negative, and neutral target words. The data show that the violent video game primed aggressive concepts as expected, but also raised positive concepts, and did so independently of the participants’ history of playing violent video games. Therefore, the results challenge the idea that violent video games inherently stimulate negative concepts only.

The role of the medial prefrontal cortex in the play fighting of rats.

Although decorticated rats are able to engage in play, their play is abnormal in three ways. First, decorticates do not display the normal, age-related shifts in defensive strategies during development. Second, decorticates do not modify their defensive tactics in response to the social identity of their partners. Third, decorticates display a global shift in defensive tactics from more complex to less complex strategies. It has been shown that lesions of the motor cortex (MC) selectively produce the abnormal developmental effects on play, and that lesions of the orbitofrontal cortex (OFC) selectively produce the deficits in behavioral discrimination between social partners. In the current set of experiments, we demonstrate that lesions of the medial prefrontal cortex (mPFC) produce the shift from more complex to less complex defensive tactics, while leaving intact the age-related and partner-related modulation of defensive strategies. Thus, we have evidence for a triple dissociation of function between the MC, the OFC, and the mPFC with respect to social play behavior.

Third-party interventions in dyadic play between littermates of domestic dogs, Canis lupus familiaris

Interventions occur when animals interfere in competitive interactions between two or more individuals. Interveners can alter the nature of the ongoing interaction by targeting one party (attacking, biting) and supporting the other. Three theories have been proposed to account for intervention behaviour: kin selection, reciprocity and direct benefits. The kin selection hypothesis predicts that interveners will selectively support relatives over nonrelatives; the reciprocity hypothesis predicts that when intervener ‘A’ supports individual ‘B’, later ‘B’ will intervene and support ‘A’; and the direct benefits hypothesis predicts that target/support patterns should serve the immediate interests of the intervener. We tested the reciprocity and direct benefits hypotheses by exploring third-party interventions in play fighting among littermates of domestic dogs. Interveners in dyadic play did not preferentially target or support preferred playmates of the intervener. Interveners targeted the dog in the losing role at the time of the intervention, and they did not show reciprocity in support. Taken together, these last two findings suggest that littermates benefit directly and use interventions opportunistically to practise offence behaviours directed at littermates already behaving subordinately. Opportunities to practise targeting in a playful setting may help structure dominance relationships among littermates. Additionally, the tendency for puppies to do what the other is doing (target the dog in the losing role) may pave the way for synchronizing cooperative behaviours during group hunting and territorial defence. The types of behaviours used to intervene changed over development, but the outcome following an intervention remained stable.

Play behavioural tactics under space reduction: social challenges in bonobos, Pan paniscus

Several studies have suggested that primates vary in their response to spatial reduction, which represents a challenge for captive animals. Under spatial reduction, primates can adopt various strategies to reduce social tension. Such strategies, which are not mutually exclusive, can involve avoidance and coping tactics. Recently, it has been shown that, during short-term crowding, bonobos may use both grooming and nonreproductive sexuality to avoid a potential rise in tension. Because bonobos are extremely playful, and play can be a risky activity, we tested whether play patterns were selectively avoided under space reduction. We collected daily data via focal animal sampling on a group of bonobos housed in the Apenheul Primate Park (Apeldoorn, The Netherlands) over a 12-month period. Among the adults, we found no difference in the contact play levels (play fighting) between the two space conditions (outdoors, 5000 m2, and indoors, 230 m2), whereas indoors, there was a tendency toward an increase in locomotor–rotational play frequency. These findings indicate that bonobos do not adopt an avoidance tactic to reduce the risk involved in space reduction. Nevertheless, dyads showing higher rates of agonistic encounters were less likely to engage in contact play sessions. Even though it is difficult to affirm that space availability significantly induced higher playmate selectivity, we found that play signals significantly increased indoors, thus suggesting the need for a clearer ‘declaration of intentions’ in an unsafe situation.

Ethanol‐Induced Social Facilitation in Adolescent Rats: Role of Endogenous Activity at Mu Opioid Receptors

Ethanol consumption is considerably elevated during adolescence. Attractiveness of alcohol for humans during the adolescent developmental period is based, in part, on its ability to induce social facilitation--a facilitation of social interactions not only evident in human adolescents but also in adolescent rats. Endogenous opioid systems are among the multiple neural systems implicated in the behavioral and reinforcing effects of ethanol and may play a substantial role in modulating stimulatory effects of low doses of ethanol on social behavior during adolescence. This possibility was explored in the present study through the use of an animal model of peer-directed social behavior. Sprague-Dawley rats were challenged early in adolescence with saline or ethanol intraperitoneally (i.p.), placed into an individual holding cage for 30 minutes, and then tested in a familiar situation with a nonmanipulated partner of the same age and sex. In Experiment 1, each test subject was injected subcutaneously with one of the three doses of a nonselective opioid antagonist naloxone (0, 0.05, and 0.1 mg/kg), 5 minutes prior to the social interaction test and 25 minutes following challenge with saline or ethanol (0.5 g/kg), whereas in Experiment 2 animals were challenged with one of the six doses of ethanol (0, 0.25, 0.5, 0.75, 1.0, and 1.25 g/kg) prior to injection of either saline or naloxone (0.05 mg/kg). In Experiment 3, animals were pretreated i.p. with the selective mu-opioid antagonist CTOP (0, 0.01, 0.025, 0.05, and 0.1 mg/kg) 30 minutes prior to challenge with saline or ethanol (0.5 g/kg). Low doses of ethanol (0.5 and 0.75 g/kg) produced social facilitation, as indexed by significant increases in play fighting and social investigation. Both doses of naloxone and the three highest doses of CTOP blocked the stimulatory effects of ethanol on play fighting but not on social investigation. These effects were not associated with alterations in ethanol pharmacokinetic properties or with shifts in the biphasic ethanol dose-response curve. Ethanol-induced facilitation of social play behavior seen in adolescent animals is mediated in part through ethanol-induced release of endogenous ligands for the mu-opioid receptor or an ethanol-associated enhancement of sensitivity of these receptors for their endogenous ligands.

Vasopressin facilitates play fighting in juvenile golden hamsters

Vasopressin facilitates aggression in adult hamsters. Whether this neuropeptide has a similar role in play fighting remains unknown. The goal of the present study was to identify whether vasopressin controls play fighting in juvenile golden hamsters as well. Juvenile male golden hamsters were tested for play fighting after microinjections of a vasopressin V1A-receptor antagonist, Manning compound, either 0, 9, or 90 µM, into the anterior hypothalamus. The treatment selectively inhibited offensive aspects of play fighting in experimental animals. Attack frequencies were significantly decreased by both doses of Manning compound. In addition, the high dose of the receptor antagonist increased attack latencies, decreased bite frequencies, and decreased the averaged number of attacks per contact bout. Together, these results show that vasopressin controls offensive behaviors throughout development from play fighting in juveniles to aggression in adults.

Social interactions and 50 kHz ultrasonic vocalizations in adolescent and adult rats

Human adolescents drink partly to facilitate their social interactions, a social facilitatory effect of ethanol also seen in adolescent rats tested under familiar test circumstances. To explore the role of hedonic affect in ethanol-induced social facilitation, this study assessed 50 kHz ultrasonic vocalizations (USVs) in pair-housed adolescent (P29–37) and adult (P71–79) Sprague–Dawley male rats during social interactions. On each of eight test days, animals were socially isolated for 3 h and then injected intraperitoneally with 0 (saline), 0.25 or 0.5 g/kg ethanol. Twenty-five minutes later they were placed alone in a familiar test chamber for a 5-min period, followed by a 10-min encounter with a similarly injected peer. USVs were recorded during this 10-min period, while social interactions were videotaped for later scoring. BECs were measured immediately post-test on day 8. Although the 0.25 g/kg dose of ethanol facilitated play fighting in adolescents but not adults, ethanol had little to no effect on 50 kHz USV production under these test circumstances. USV production was higher in adults than adolescents, despite adolescents consistently engaging in more social behavior. To the extent that 50 kHz USVs index the hedonic value of social interactions, these findings support the conclusion that elevations in social behavior normally evident in adolescents may not be related to increases in hedonic sensitivity for social stimuli.

Adult play fighting and potential role of tail signals in ringtailed lemurs (Lemur catta).

Adult strepsirrhines have been completely neglected in the study of animal play. I focused on adult play fighting and the role of tail-play as a signal in ringtailed lemurs (Lemur catta). Tail-play is performed during play fighting, when lemurs anoint or, more rarely, wave their tails toward the playmate. During the prereproductive period, male and female lemurs engaged in play fighting with comparable frequencies, as was expected to occur in monomorphic species such as L. catta. The dyads showing low aggression rates engaged most frequently in play fighting, and polyadic play was frequently performed. Signals seem to be important in avoiding escalation to real aggression, especially when the playfulness of performers can be misunderstood by recipients. Tail-play was most frequent (a) in the dyads with low grooming rates (low familiarity degree) and (b) during the most risky play sessions (polyadic ones). Thus, tail-play can be considered as a useful tool for play communication in ringtailed lemurs.

Violent Content Enhances Video Game Performance

This study assesses the impact of violent video game content on players’ game performance. According to the desensitization hypothesis ( Carnagey, Anderson, & Bushman, 2007 ), violent content may elicit negative affective responses and inhibitions, which in turn should interfere with performance. On the other hand, the players might understand virtual violent acts as a digital form of rough-and-tumble play, associated with positive emotions and mobilization, which in turn should raise performance. To test these competing hypotheses on game performance, N = 50 males with no prior violent gaming experience were exposed to three different versions of a custom-made video game in which the actions to be performed were identical, though they were audio-visually presented to appear either nonviolent, moderately, or extremely violent. The results show no indication of an initial inhibition of aggressive behavior, that is, performance is elevated and remains so if the action is presented audio-visually as being violent. This supports the notion that being involved in violent video game activity is perceived as an essentially harmless acting-out of playful fighting behavior.

Cerebral abscess in term newborn with perinatal asphyxia: The importance of cerebral ultrasound monitoring

Potentiating social, cognitive, and sensorimotor stimulations the Environmental Enrichment (EE) increases levels of novelty and complexity experienced by individuals. Growing evidence demonstrates that parental EE experience, even occurring in the pre-reproductive phase, affects behavioral and neural developmental trajectories of the offspring.To discover how the accumulation of early maternal complex experiences may inform and shape the social behavior of the following generation, we examined the effects of pre-reproductive enrichment of dams (post-natal days 21–72) on the play performances of their male and female adolescent offspring. Furthermore, we examined the effects of pre-reproductive enrichment on maternal behavior (during post-partum days 1–10) and male intruder aggression (on post-partum day 11). Since oxytocin modulates maternal care, social bonding, and agonistic behavior, the number of oxytocinergic neurons of the paraventricular (PVN) and supraoptic (SON) nuclei was examined in both dams and offspring.Results revealed that enriched females exhibited higher levels of pup-oriented behaviors, especially Crouching, and initiated pup-retrieval more quickly than standard females after the maternal aggression test. Such behavioral peculiarities were accompanied by increased levels of oxytocinergic neurons in PVN and SON. Moreover, pre-reproductive maternal EE cross-generationally influenced the offspring according to sex. Indeed, male pups born to enriched females exhibited a reduced play fighting associated with a higher number of oxytocinergic neurons in SON in comparison to male pups born to standard-housed females.In conclusion, pre-reproductive EE to the mothers affects their maternal care and has a cross-generational impact on the social behavior of their offspring that do not directly experiences EE.This article is part of the Special Issue entitled “Neurobiology of Environmental Enrichment”.

The influence of natural variations in maternal care on play fighting in the rat

Naturally occurring variations in maternal care in the rat influence the sensitivity of offspring to stress in adulthood. The offspring of mothers that show lower levels of pup licking/grooming (i.e., low-LG mothers) demonstrate enhanced responses to stress and increased anxiety compared to those of high-LG mothers. Low-LG offspring are also more sensitive to the influence of environmental enrichment than high-LG offspring. This study examined play fighting in the juvenile offspring of high-LG and low-LG dams in a multiple-play partners housing environment. Male offspring from low-LG dams demonstrated a significantly higher frequency of pouncing, pinning and aggressive social grooming than did high-LG males and high-LG and low-LG females. Consistent with earlier reports, male pups engaged in more play fighting than did females and maternal care was associated with differences in play fighting but only in males. Lower levels of stimulation in the form of LG from the dam during perinatal development may thus increase sensitivity for the stimulating effects of play behavior in periadolescence, in part explaining the increased solicitation of play fighting through increased pouncing in the male offspring of the low-LG mothers. These findings identify a possible influence of variations in maternal care on play fighting and suggest that maternal care in the perinatal period influence social interactions during periadolescence.

Neural circuitry of play fighting in golden hamsters

In hamsters, play fighting matures gradually into adult aggression. As these two behaviors share many similarities in this species, we predicted that a single neural circuitry controls their offensive component. The goal of the present study was to identify neural systems associated with offensive play fighting in male juvenile golden hamsters. The neural circuitry related to this behavior was identified through quantification of c-Fos immunolabeling. We also looked for vasopressin cells possibly associated with play fighting. We found that areas previously associated with offensive aggression in adult hamsters, including the ventrolateral hypothalamus, the medial amygdala, and the bed nucleus of the stria terminalis, also showed enhanced c-Fos expression after play fighting. In addition, vasopressin neurons in the nucleus circularis and the medial division of the supraoptic nucleus expressed enhanced c-Fos immunolabeling in juveniles after play fighting, as previously reported in adult hamsters after aggression. Finally, enhanced c-Fos expression associated with play fighting was also found in areas previously unexplored in adult hamsters, such as the prefrontal cortex. Together, our results support the hypothesis of a single core neural circuitry controlling the offensive components of play fighting and adult aggression throughout puberty in hamsters.

Adolescents’ perceptions of violence and its prevention

To explore aspects of aggression, in particular fighting and weapon carrying, among high school students. This was in response to an earlier survey of Dunedin young people and will assist in the development of a broader quantitative study on aggression among high schools students. A qualitative investigation using eight focus groups of 41 participants was conducted in Otago, New Zealand, between November 2004 and February 2005. The focus groups were analysed to identify common themes and critical issues. Results suggest there are different levels of fighting, but participants agreed that a fight should be defined as serious as opposed to a play fight. Fights often begin as verbal and escalate to physical. Differences were found in fighting at school and outside of school. Whether an item was considered a weapon or not depended on the intended use of the item. Participants suggested that some items may be reported as weapons, even though they are not being carried for such purposes. If so, the estimates provided in the prior Dunedin survey may be unduly high. Surveys such as the Youth Risk Behaviour Survey provide a snapshot of youth aggression, but may hide significant differences in the nature of the aggression being reported. Prevention should concentrate on changing the social environment of our schools and communities. Further research should include more in-depth questions on fighting and weapon carrying, both at school and outside of school, to better estimate the prevalence of these behaviours and the context in which they occur.

Rough-and-Tumble Play and the Development of the Social Brain

Social play—that is, play directed toward others—is a readily recognizable feature of childhood. In nonhuman animals, social play, especially seemingly competitive rough-and-tumble play or play fighting, has been the most studied of all forms of play. After several decades of study, researchers of play fighting in laboratory rats have pieced together the rudiments of the neural mechanisms that regulate the expression of this behavior in the mammalian brain. Furthermore, the understanding of the organization, development, and neural control of play in rats has provided a model with which to examine how the experiences accrued during play fighting can lead to organizational changes in the brain, especially those areas involved in social behavior.

Postnatal exposure to cocaine in rats housed in an enriched environment: effects on social interactions

This study was undertaken to evaluate the effects of environmental enrichment (EE) in rats exposed to cocaine during the first month of postnatal life by examining several categories of social behaviour (play fighting, social investigation, comfort behaviours and invitation to play). Wistar rats were divided in four groups: pups exposed to cocaine hydrochloride (15 mg/kg body weight/day), sc, in two daily doses, from postnatal day (PND) 1 to 28 and reared in EE; exposed to cocaine as previously described and reared in standard environment (SE); saline-exposed and reared in EE; pups saline-exposed and reared in SE. On PND 21, 24 and 28, social interactions were examined for 10 min. Results show that cocaine animals reared in SE decreased the frequency of play solicitation. Control animals reared in EE exhibited decreased play fighting and social investigation behaviours compared to SE-reared rats. Animals postnatally exposed to cocaine when reared in EE displayed more comfort and invitation to play behaviours and decreased social investigation compared with SE-reared animals. The results suggest that in rats postnatally exposed to cocaine, EE rearing elicited differences in both processing of environmental stimuli and a response to social challenges.

The modulation of play fighting in rats: Role of the motor cortex.

The cortex is not necessary for rats to engage in play fighting, but it is necessary for them to modify their pattern of play fighting in different contexts. Two experiments were conducted to determine the role of the motor cortex (MC). Rats with bilateral ablations of the MC performed on Postnatal Day 10 failed to show the normally present age-related modulation in defense but were able to modulate defense with different social partners. This latter finding was confirmed in rats given ablations as adults, in which responses to social status could be monitored before and after brain damage. It appears that different forms of cortical modulation of play fighting involve different cortical circuits.

Prenatal Exposure to Cocaine and Enriched Environment

Exposure to cocaine throughout gestation may produce several deleterious outcomes in the offspring that include effects on neurotransmitter systems and structure of the central nervous system. Such changes are most likely correlated with behavioral alterations. Environmental enrichment (EE) in early stages is a factor that affects structural and behavioral development. This article examines the effects, upon social interactions, of EE during the first month of life in rats prenatally exposed to cocaine. Wistar dams were subcutaneously exposed to 60 mg/kg of cocaine divided in two daily doses from gestational day (GD)8 to GD22. Pair-fed controls were given saline vehicle in the same protocol. Offspring were distributed to the different environments in four experimental groups. Group 1: offspring from dams prenatally exposed to cocaine as previously described and reared in EE from postnatal day (PND)1 to PND28; Group 2: pups from cocaine-exposed dams and reared in a standard environment (SE); Group 3: pups from pair-fed saline-exposed dams and reared in EE; Group 4: offspring from saline-exposed dams and reared in SE. On PND21, 24, and 28, rats were examined in several social behavioral categories (play fighting, social investigation, comfort behaviors, and solicitation to play) for 10 min. Animals reared in SE do not display any differences due to treatment in the behavioral categories analyzed. Control offspring reared in EE presented decreased play fighting, decreased solicitation to play, and decreased social investigation compared to the control SE group, while cocaine-exposed animals reared in EE did not present these variations. These results suggest that EE rearing may unmask hidden effects of prenatal cocaine exposure.