Noninvolvement of testosterone in aggressive defense behavior in the male blind mole rat Spalax ehrenbergi

Blind mole rats (Spalax ehrenbergi) are solitary and aggressive subterranean rodents. Aggressive defense behavior in the mole rat functions to deter neighboring competitors from territory, food, and mates and includes seismic and odor signals. The aim of the present study was to determine whether the aggressive defense behavior displayed by male mole rats is testosterone dependent. Five behavioral variables were taken as being representative of such aggressive interaction: exposing teeth, biting, bulldozing movements of the head, soil blocking, and self‐grooming. We monitored male testosterone levels and aggressiveness throughout the annual cycle, which can be divided into three main climatic periods: cold and rainy (September–February); warm, during which the soil is still moist and easily excavated (March–May); and hot (June–August), when the soil is hard and dry. In a second experiment the effect of endogenous and exogenous testosterone on male aggressive defense behavior was determined before and after castration and following testosterone propionate replacement. We found fluctuations in male testosterone concentrations, with three peaks: in November, May, and August, one in each of the three climatic periods. However, these fluctuations did not correlate with male aggressive behavior, which remained constant throughout the year. Furthermore, because neither castration nor testosterone propionate replacement in castrated individuals affected their defense behavior, we suggest that such behavior in male mole rats is testosterone independent. The continuous excavation and maintenance of the mole rat’s underground tunnel system demands high energy expenditure year‐round and constant defense of territory sites and food caches from intraspecific rivals. Thus, although testosterone may fluctuate as a result of seasonal breeding cycles, constant high levels of aggressive defense throughout the year are crucial for the survival of the male mole rat in its solitary subterranean environment. Aggr. Behav. 27:64–72, 2001. © 2001 Wiley‐Liss, Inc.     

Effects of acute administration of nicotine and lobeline on agonistic encounters in male mice

The effects of acute administration of two nicotinic ligands, (‐)‐nicotine and (‐)‐lobeline were examined on isolation‐induced aggression in mice. Individually housed male mice confronted anosmic “standard opponents” in a neutral arena 10 min after drug administration. Encounters were videotaped and evaluated using an ethologically based analysis facilitating estimation of time allocated to 11 broad behavioral categories. Nicotine did not have significant effects on threat or attack but significantly diminished time allocated to digging. The lowest dose of lobeline significantly diminished attack and induced a slight increase of immobility without significantly diminishing other behaviors with motor components. The intermediate and highest dose of lobeline reduced time allocated to all behaviors with motor components. It is concluded that these two nicotinic agonists produce different behavioral profiles during agonistic encounters in mice but that this test may not facilitate assessing the impact of such drugs on irritability. Aggr. Behav. 26:376–385, 2000. © 2000 Wiley‐Liss, Inc.     

Interpolating physical exercise between instigation to aggress and aggression: The role of irritability and emotional susceptibility

Two studies were conducted using the Buss aggression machine paradigm to investigate the mediational role of physical exercise with respect to subsequent aggression in relation to the presence or absence of previous instigation. The irritability level of subjects was taken into account in the first study, and the subject' emotional susceptibility level in the second study. In both studies sex differences were also considered so that each study resulted in a 2 × 2 × 2 × 2 design with ten subjects in each cell. As far as irritability is concerned, experimental subjects (pedaling on a bicycle ergonometer) delivered higher shocks than controls (who just waited out the 10 min the experimental subjects were pedaling), independent of irritability level or of the presence or absence of previous instigation. When emotional susceptibility was taken into consideration, physical exercise associated with high level of emotional susceptibility and previous instigation resulted in increased intensity of the shocks subsequently delivered. These findings are discussed in terms of the importance of stable personality characteristics that may differentially mediate aggression.     

累积生态风险对农村初中生攻击行为的影响：有调节的中介模型

本研究旨在探讨累积生态风险与农村初中生攻击行为之间的关系,以及道德推脱的中介作用与共情的调节作用。通过对845名农村初中生进行问卷调查,结果发现：（1）农村初中生累积生态风险、道德推脱与攻击行为两两之间均存在显著正相关;（2）道德推脱在累积生态风险与农村初中生攻击行为之间起部分中介作用;（3）共情调节道德推脱在累积生态风险与攻击行为之间的中介效应,相对于共情水平较高的农村初中生,中介效应在共情水平较低的农村初中生中更显著。     

Role of serotonin in human aggressive behaviour

This study aimed to evaluate a peripheral serotonergic marker, ³H-imipramine (³H-IMI) binding to platelet membranes, in a group of severely aggressive subjects (A), institutionalized since childhood for mental retardation, as compared with suicide attempters (S) and healthy controls (H). The maximum binding capacity of ³H-IMI to platelet membranes was statistically lower in (A) and (S) than in (H). In addition, a statistically significant difference was observed between the Bmax values of aggressive subjects and those of suicide attempters. No changes in the dissociation constant (Kd) of IMI binding were observed. These data provide further supporting evidence for the hypothesis of an abnormality of the 5HT system in aggressive behaviour and suggest that such an abnormality, as reflected by platelet markers, is more severe in suicide attempters. © 1993 Wiley-Liss, Inc.     

Influence of contextual information on observers' perceptions of actors' intentions to harm others

Previous examinations of perceptions of aggressive behaviors have used static stimulus presentations (e.g., photographs or slides). This investigation examined the impact of varying amounts of geographical and temporal contextual information on observers' perceptions of actors' intentions to physically and psychologically (intimidate) harm others. Participants (51 elite ice hockey players) were randomly assigned to view one of three video-taped presentations showing eight ice hockey behaviors in either a) a dynamic mode with contextual information, b) a dynamic mode with no context, or c) a static, “freeze-frame” mode. MANOVA results showed that non-aggressive stimuli were perceived as less aggressive, and aggressive stimuli were perceived as more aggressive in dynamic presentations with context than in static presentations. Based on these findings, it is suggested that future research focussing on perceptions of aggressive behavior utilize a dynamic stimulus presentation containing context material. © 1996 Wiley-Liss, Inc.     

Aggressive behaviour in free-ranging guanacos and vicuñas in Argentina

The aggressive behaviour of free-ranging guanacos and vicuñas, living in sympatry in Catamarca Andes, Argentina, was analysed in relation to their social organisations. These organisations include territorial family units, solo males (territorial or not), and bachelor groups. In both guanacos and vicuñas, family groups tended to have higher rates of agonistic interactions than bachelors and to be frequently involved in aggressive encounters, whereas bachelor groups showed the opposite tendencies. Encounters between family groups and solo males were more frequent than expected. Bachelors acted almost exclusively as recipients of aggressive interactions, whereas solitary and family males frequently initiated encounters. Family groups adopted different behaviours towards bachelors in the two camelids. In guanacos, the latter were simply ignored, whereas in vicuñas (where they tend to compete for food with families) bachelors were consistently attacked by families. The behaviour of solitary males showed the main difference between the two species. Guanaco solo males had a much more aggressive attitude than vicuña counterparts. Their proportion in guanaco population was also unexpectedly high. These results suggest that, in the less rigid organisation of guanaco society, the behaviour of solitary males is adopted by a number of adult males in an attempt to breed. © 1996 Wiley-Liss, Inc.     

Maternal territoriality as an offspring defense strategy in red swamp crayfish (Procambarus clarkii,Girard)

The offspring‐defense hypothesis of maternal territoriality in solitary and semisocial mammals [Wolff JO and Peterson JA. 1998. Ethol Ecol Evol 10:227–239] was evaluated in another taxon using maternal and nonmaternal female red swamp crayfish (Procambarus clarkii), a freshwater decapod crustacean that shows pronounced shelter‐related maternal aggression. The maternal females were of three different categories: (1) ovigerous, (2) carrying primarily stage 1 offspring, or (3) tending offspring that were primarily stage 2. Each female was in residence in an individual aquarium containing only a gravel substrate for 24 hr prior to serial intrusions by male conspecifics. Virtually all of the residents, maternal and nonmaternal, excavated a depression (shelter) in the substrate prior to the first intrusion. The results showed that residents in each of the maternal categories won a significantly higher proportion of their encounters than did the nonmaternal residents, which showed only negligible defense and lost every encounter. However, there were no significant differences in encounter outcomes between the maternal resident categories. There was clear defense of the shelter by maternal females, with virtually all fighting being in or around it, thus demonstrating stable, heightened territorial defense throughout these maternal phases of reproduction. This support of the offspring‐defense hypothesis of maternal territoriality is the first such evidence for a freshwater crustacean and is very similar to that recently reported in a related marine decapod, the American lobster (H. americanus). Aggr. Behav. 27:391–403, 2001. © 2001 Wiley‐Liss, Inc.     

THE USE OF PEER MONITORS TO REDUCE NEGATIVE INTERACTION DURING RECESS

The negative interactions of a mildly retarded child, Dennis, were reduced in three daily recess periods, withthe use of a point system. Adult monitors initiatedthe intervention inthe morning recess; reductions achieved during adult monitoring were maintained in that recess during two subsequent conditions: peer monitoring and self-monitoring. Dennis' negative interactions were reduced next inthe afternoon recess by peer monitors. Again, reductions were maintained during a subsequent self-monitoring condition. Finally, duringthe noon recess, Dennis was trained to serve as a peer monitor for Ed, a moderately retarded classmate. Dennis' rate of negative interactions quickly decreased following his appointment as a peer monitor. The results show that a point system, originally designed for adult monitoring, can be adapted without loss of program effectiveness for peer monitoring or self-monitoring. The results also suggest that classmates who serve as peer monitors may benefit significantly from their role. The conditions under which these therapeutic effects occur andthe role that treatment order effects may play in this process require further investigation.