Evidence for a motor mechanism of pain-induced aggression instigation in humans

The automatic skeletal motor responses of 20 male and 20 female student subjects (aged 20–36) receiving a painful stimulation (electric shock) were studied by examining voluntary concomitant extensions and flexions of the arm. These movements were either of long duration, allowing for an on-line control of their execution or, of short duration, requiring extensive pre-programming. Subjects were instructed either to push or to pull a lever upon receipt of an acoustic signal, which was paired or unpaired with an electric shock. Latencies for long duration movements (regardless of direction) were reduced by reception of painful stimulation. Latencies of short duration extensions and flexions were respectively reduced and increased by painful stimulation. Latencies of short duration movements were larger for females than males, regardless of movement direction. These data suggest that painful stimulation elicits automatic movements which affect programming of the termination of simultaneous voluntary movements. Implications of these findings for the study of aggressive behavior are discussed. © 1994 Wiley-Liss, Inc.     

Sex differences in maternal behaviors of immature rats: The role of emotionality

Immature rats are able to give maternal care to pups and may increase their inclusive fitness by helping newborn siblings. Immature males are generally reported to be more maternal than females. In this research we studied sex differences and the extent to which they may be due to a different emotional response to novelty. We studied maternal response in two groups of immature rats of both sexes: in the naive group, juveniles aged from 18 to 30 days were given one test and showed clear-cut sex differences. The experience group was submitted to repeated tests from 18 to 30 days of age, thus eliminating the effects of novelty: as a result, all differences between sexes disappeared. A second experiment was designed in 24-day-old females to differentiate the effects of repeated handling and exposure to the test situation from that of repeated exposure to pups; moreover, the effects of an anxiety-reducing drug (diazepam) were studied. Exposure to pups is particularly efficient in facilitating maternal response. Diazepam injection was also effective, but its control showed that the injection per se was responsible for the effect. In conclusion, our results stress the importance of response to novelty and suggest that sex differences in maternal behavior of immature rats may be modulated by different emotional responses by males and females. In fact, emotionality competes with, and may exert an inhibitory effect on, the expression of a vast array of behaviors. © 1994 Wiley-Liss, Inc.     

Variation in aggressive behavior and anatomo-physiological correlates generated by crowding without physical contact in the house mouse

Behavioral, physiological (i.e., endocrine), and anatomical consequences of crowding in mice were studied in a situation where animals were in auditory, visual, olfactory, and tactile contact but restrained from full physical interactions, to prevent overt aggression. Males that cohabited with females undisturbed by neighboring conspecifics showed greater propensity to attack same-sex intruders and had higher plasma testosterone levels than did their “crowded” counterparts, that is, males cohabiting with females and housed adjacent to other male/female pairs. In this respect, the latter animals resembled submissive males. However, a significant increase in weight of androgen-dependent target organs (i.e., seminal vesicles and preputial glands) was found in crowded males. These data indicate that despite the observed inhibition of social aggression these males are not physiologically comparable (homologous) to male mice that experienced defeat and the stress of submission during fighting. The intriguing possibility that different conversion pathway of testosterone are accelerated, as a result of social communication, in males living in these two environments and the behavioral implications of these possibilities are discussed. Finally, the parental behavior of crowded animals, although not freely interacting with each other, was disrupted, causing a marked decrease in reproductive success. In this situation a high incidence of infanticide of their offspring by both parents was observed, whereas this behavior was virtually absent in non-crowded male/female pairs.     

Synchronicity and “Being Endowed with Meaning”

Jung developed over 50?years a paradigmatic idea of an acausal principle, which he called synchronicity. His hypothesis on synchronicity states that, complementary to causality, there exists a further explanatory principle whose effects appear as acausal but meaningful events. Therewith Jung added to the triadic principles of space, time and causality a fourth principle: synchronicity. The experience of individual synchronicities points to a general acausal and meaningful orderedness in nature which apparently exists outside man. Jung published Answer to Job and Synchronicity at the same time, for he attempted to open up a new path to the “state of spiritualization” Beseeltheit of Matter by making the assumption that “being is endowed with meaning.” According to Jung there exists a latent meaning in the cosmos, which existed long before human consciousness developed. He believed that “on the organic level it might be possible to regard biological morphogenesis in the light of the synchronistic factor.” One of many examples in the biological evolution is a Cretaceous-Palaeogene worldwide catastrophe approx. 65 million years ago that resulted in the mass extinction of the dinosaurs. It is understood as the result of a meteorite impact. This catastrophe was a most meaningful chance from the point of view of the mammals, including modern man. We modern humans finally came into existence thanks to a series of cosmic happenings, which were based on causality and synchronicity. What is true for our personal individuation is also true for biological or historical developments: an acausal but meaningful principle is secretly at work.     

The effects of negative reinforcement for irritable aggression on resident-intruder behavior

This experiment demonstrated that rats trained to display elevated levels of shock-induced aggression in a negative reinforcement paradigm displayed more boxing behavior than yoked control groups in a later test in which intruder rats were placed in the home cage of resident rats. Resident or intruder status did not affect the influence of the negative reinforcement procedure on the observed resident-intruder behavior of trained animals; however, naive intruders paired with trained residents displayed increased defensive behavior, suggesting that negative reinforcement for shock-induced aggression affected the behavior of these residents.     

Aggressive Behavior and Peer Social Status of Elementary School Children

The relation between aggression and peer social status was investigated in a group of 238 third-through fifth-grade children. Peer social status refers to the degree to which a child is accepted by his or her peer group. By asking children to nominate peers they “like most” and “like least,” one can identify children who are popular, rejected, neglected, or viewed as average within their peer group. Results indicated low to moderate correlations between peer-nominated aggression and global indices of social acceptance. More specifically, it was found that aggressive children largely comprised the rejected and average social status groups, but not the popular or neglected groups. Furthermore, analyses indicated that according to both peers and teachers, aggressive/rejected children showed academic and social-skill deficits, whereas aggressive children of average peer status exhibited adequate adjustment similar to that of nonaggressive/average-status children. These results suggest the importance of considering peer social status when identifying aggressive children in need of intervention and in determining which skill deficits to address. In addition, knowledge of an aggressive child's peer status might be useful in enhancing the predictability of adult adjustment.     

Autoradiography of hypothalamic regions after acute hyperosmolarity in mice

Many regions around the third ventricle of the brain are thought to participate in the regulation of water intake. In this study we have visualized in acutely hyperosmolar mice the hypothalamic regions by using autoradiography and [14C]deoxyglucose as marker. By applying a recently published, inexpensive, calibrated photographic method for the analysis of the autoradiographs, we can show that the medial parts of the hypothalamus near the third ventricle increased their uptake of deoxyglucose in comparison with the lateral parts. Densitometric measurements confirmed the results. The results also indicate that parts of the medial hypothalamus, even those that are more caudal than the paraventricular nuclei, react to hyperosmolarity.