Effects of apomorphine on mating behavior, flank marking and aggression in male hamsters

In male rats, the dopamine agonist apomorphine (APO) generally facilitates copulatory behavior. However, disruptive effects of high APO doses have been reported. These have been interpreted in diverse ways, as products of a dopaminergic system that inhibits sexual behavior or as consequences of APO's stimulation of competing responses. To test the generality of these effects, we observed APO's impact on copulatory behavior in male hamsters. Several effects were observed, all attributable to a relatively high dose and involving the disruption of male behavior. More unexpectedly, APO treatment caused males to attack estrous stimulus females in the course of these tests. To clarify these effects, we observed the effects of APO on flank marking, a type of scent marking closely allied to aggression and dominance in hamsters. Treatment reliably decreased the latency of marking. It also increased the rate of marking when appropriate measures were taken to prevent this effect from being obscured by drug-induced cheek pouching. Together, these results confirm and extend APO's well-known ability to increase aggression. Further, they suggest that APO-induced aggression can intrude into other contexts so as to disrupt, or possibly facilitate, other forms of social behavior.

The Effects of Apomorphine on Sexual Behavior and Aggression in Male Golden Hamsters

The general dopamine agonist apomorphine has been shown to have mostly facilitative effects on sexual behavior in rodents (Domingues & Hull, 2005; Bitran & Hull, 1987). A study looking at the effectsof apomorphine on sexual behavior in male golden hamsters observed that after systemic injections of apomorphine the males became aggressive towards the estrous females (Floody, unpublished). Studies on aggressive behavior have shown that apomorphine has facilitative effects on aggression in rodents (Nelson & Trainor, 2007; van Erp & Miczek, 2000; Ferrari, van Erp, Tornatzky, & Miczek, 2003). The studies presented here attempt to unravel the effects that apomorphine has on sexual and aggressive behavior in male golden hamsters. Studies 1, 2, 3, and 4 focused on the effects of apomorphine on aggression and Study 5 focused on the effects of apomorphine on sexual behavior. It was important for the purposes ofthis study to have separate, specific measures of aggression and sexual behavior that did not involve a social context that would involve multiple behaviors and motivations. The measure used to assessaggression was flank marking behavior. The measure used to assess sexual behavior was the number of vocalizations in response to sexual stimuli. The results from Studies 1, 2, and 3 suggested thatapomorphine increased aggressive motivation in a dose-dependent manner. In Studies 1 and 2 there was a high occurrence of stereotyped cheek pouching that interfered with the flank marking behavior. In Study 3 the procedure was modified to prevent cheek pouching and flank marking was observed uninhibited. Study 5 suggested a decrease in vocalizations after apomorphine treatment. However, this decrease may have been a result of the increase in stereotyped licking behavior. Results suggested that systemic apomorphine treatments increase aggressive motivation in hamsters. The increase in aggressive motivation may confuse the perception of the sensory signals that the males receive from the estrous females. They may haveperceived the estrous female as a nonestrous female which they would normally associate with an aggressive interaction (Lehman, Powers, & Winans, 1983).

The Impact of Parental Psychological Control on College Students’ Relational Aggression and Friendship Quality

The present study investigated the relationships between parental psychological control and college students’ relational aggression and friendship quality. Based on previous research, it was expected that parents’ use of psychological control would be associated with students’ increased use of relational aggression with peers and lower friendship quality. Students completed a series of survey measures assessing their mothers’ and fathers’ use of psychological control, behavioral control, and warmth/acceptance. Students also completed a series of survey measures assessing their friendship quality, social skills, relational aggression, self-esteem, and social desirability. The study’s findings revealed that parental psychological control was associated with and predicted students’ increased use of relational aggression with peers. Parental psychological control was also associated with students’ lower friendship quality. However, parents’ use of psychological control did not predict students’ friendship quality after accounting for the influence of students’ personal and peer relationship variables. This finding suggests that characteristics of peer relationships may play a larger role than parenting behaviors in shaping college students’ friendships. The study also found that students who displayed higher levels of relational aggression had lower quality friendships. Other findings revealed that the relationship between parental psychological control and students’ friendship quality can be partially explained by students’ use of relational aggression with peers. Students’ friendship quality can also help to explain the influence of parental psychological control on students’ relational aggression. In addition, the study found that combinations of parenting behaviors were more informative predictors of students’ relational aggression and friendship quality than psychological control alone. Finally, this study revealed the importance of assessing participants’ social desirability when measuring sensitive personal qualities such as relational aggression, friendship quality, and self-esteem. Overall, this study contributes to the field of research on parental psychological control by revealing its effects on college students’ relational aggression and friendship quality.

Witnessing reconciliation reduces arousal of bystanders in a baboon group (Papio hamadryas hamadryas)

Reconciliation is the occurrence of friendly behaviour between opponents shortly after an aggressive conflict. In primate groups, reconciliation reduces aggression and post-conflict arousal. Aggression within a group can also increase arousal of bystanders (e.g. increase bystanders’ rates of self-directed behaviour). Since reconciliation reduces aggression between opponents, we tested whether it also reduces self-directed behaviour in bystanders. Following aggression in a captive group of hamadryas baboons, one observer conducted a focal sample on one of the combatants to document reconciliation and a second observer simultaneously conducted a focal sample on a randomly selected bystander. Matched control observations were then collected on the same individuals in a nonaggressive context to obtain baseline levels of behaviour. The self-directed behaviour of bystanders was elevated after witnessing a fight compared to baseline levels. If combatants reconciled aggression, bystander rates of self-directed behaviour significantly decreased. If combatants did not reconcile aggression, bystander rates of self-directed behaviour remained at elevated levels, significantly higher than after reconciliation. If combatants affiliated with partners other than their original opponent, bystander rates of self-directed behaviour did not decrease. The rate of bystander self-directed behaviour after a combatant affiliated with its opponent was significantly lower than the rate after a combatant affiliated with other animals. Witnessing aggression increased arousal in bystanders, and reconciliation between the combatants was accompanied by reduced bystander arousal. The reduction was specific to contexts in which former opponents interacted. We suggest that bystanders recognized the functional significance of this conflict resolution mechanism when it occurred in their group.

Witnessing reconciliation reduces arousal of bystanders in a baboon group (Papio hamadryas hamadryas)

Reconciliation is the occurrence of friendly behaviour between opponents shortly after an aggressive conflict. In primate groups, reconciliation reduces aggression and postconflict arousal. Aggression within a group can also increase arousal of bystanders (e.g. increase bystanders' rates of self-directed behaviour). Since reconciliation reduces aggression between opponents, we tested whether it also reduces self-directed behaviour in bystanders. Following aggression in a captive group of hamadryas baboons, one observer conducted a focal sample on one of the combatants to document reconciliation and a second observer simultaneously conducted a focal sample on a randomly selected bystander. Matched control observations were then collected on the same individuals in a nonaggressive context to obtain baseline levels of behaviour. The self-directed behaviour of bystanders was elevated after witnessing a fight compared to baseline levels. If combatants reconciled aggression, bystander rates of self-directed behaviour significantly decreased. If combatants did not reconcile aggression, bystander rates of self-directed behaviour remained at elevated levels, significantly higher than after reconciliation. If combatants affiliated with partners other than their original opponent, bystander rates of self-directed behaviour did not decrease. The rate of bystander self-directed behaviour after a combatant affiliated with its opponent was significantly lower than the rate after a combatant affiliated with other animals. Witnessing aggression increased arousal in bystanders, and reconciliation between the combatants was accompanied by reduced bystander arousal. The reduction was specific to contexts in which former opponents interacted. We suggest that bystanders recognized the functional significance of this conflict-resolution mechanism when it occurred in their group. (c) 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Audience Effects in COgnitive Task Performance in Capuchin Monkeys (Cebus apella)

Primates as a taxonomic Order have the largest brains corrected for body size in the animal kingdom. These large brains have allowed primates to evolve the capacity to demonstrate advanced cognitive processes across a wide array of abilities. Nonhuman primates are particularly adept at social learning, defined as the modification of behavior by observing the actions of others. Additionally, primates often exploit resources differently depending on their social context. In this study, capuchin monkeys (Cebus apella) were tested on a cognitive task in three social contexts to determine if social context influenced their performance on the task. The three social contexts included: alone, having a dominant individual in an adjacent compartment, and having a subordinate individual in the adjacent compartment. The benefits to this design were thatthe social context was the only variable influencing performance, whereas in previous studies investigating audience effects other animals could physically and directly influence a subject's performance in an open testing situation. Based on past studies, Ipredicted that the presence of a dominant individual would reduce cognitive task performance compared to the other conditions. The cognitive test used was a match-tosample discrimination task in which animals matched combinations of eight geometric shapes. Animals were trained on this task in an isolated context until they reached a baseline level of proficiency and were then tested in the three social contexts in a random order multiple times. Two subjects (Mt and Dv) have successfully completed trials under all conditions. Results indicated that there were no significant difference in taskperformance across the three conditions (Dv x^2 (1) = 0.42, p=0.58; Mt x^2 (1) = 0.02, p=0.88). In all conditions, subjects performed significantly above chance (i.e., 39/60 trials determined by a binomial distribution). Results are contrary to previous studies thatreport low status monkeys 'play dumb' when testing in a mixed social context, possibly because other studies did not account for aggressive interference by dominants while testing. Results of this study suggest that the mere presence of a dominant individualdoes not necessarily affect performance on a cognitive task, but rather the imminence of physical aggression is the most important factor influencing testing in a social context.

The contexts of scratching behavior and postconflict behavior in squirrel monkeys (Saimiri sciureus)

Self-directed behavior (SDB), such as scratching, is a reliable indicator of emotional arousal in non-human primates. In contrast, affiliative behavior, such as social grooming, has been shown to have a calming effect in primates and reduce arousal. In order to test whether the expression of SDB was related to arousal, the scratching behavior of eight captive squirrel monkeys (Saimiri sciureus) was compared across four social contexts (huddling, proximity to others, solitary and post-conflict). In addition,rates of scratching were examined before and after affiliative behavior during the postconflict context. I tested for this effect by using the post-conflict/matched control(PC/MC) method in which post-conflict (PC) behavior of an animal is compared to thebehavior of the same animal in a baseline, nonaggressive situation or a matched control(MC). Context and associated scratching data were obtained from a total of 98 hours of focal sample data. Scratching was significantly lower while animals were huddling thanthe other two contexts. Scratching rates while solitary were significantly higher than those occurring while animals were in proximity. Scratching was also higher in PC than MC. Following conflict, animals were significantly more likely to make contact withthird parties not involved in aggression. Most of these (79%) were a third party approaching a combatant. Further, scratching rates decreased following post-conflict third party contacts and the decrease was not due to a general decrease in scratching thatmight have been occurring after the aggressive interaction. Huddling behavior appears to reduce arousal in squirrel monkeys and may act as a tension-reduction mechanism. The elevated scratching in the solitary context may suggest that squirrel monkeys may be engaged in activities while solitary, such as vigilant behavior that may increase arousal. The third party post conflict affiliative contacts observed were the first such interactions observed in squirrel monkeys. The fact that these third contacts reduced scratching ratesin the combatants indicates that 'consolation' may have been demonstrated in this species. The overall pattern of results suggested that scratching was reliable behavioral indicator of anxiety in squirrel monkeys. These results indicate that overt behavior can be used to assess emotional states in this and other species, acting as a mediator to understanding how emotions regulate social behavior.