Neil I. Wiener

Male Age Composition and Severity of Conflicts

From a behavioral ecology perspective, all forms of warfare are instances of collective aggression perpetrated predominantly by coalitions of young men. Such coalitions are manifestations of cross-cultural sex differences in aggressive behavior and may be conceptualized as a form of intrasexual competition, occasionally to obtain mates, but more often to acquire resources for the attraction and retention of mates. All societies have young males, yet wars are discrete events that can take place even after long periods of peace. Therefore, an additional factor is needed to explain the episodic nature of the phenomenon. We have proposed (Mesquida and Wiener, 1996) that the most reliable factor in explaining episodes of coalitional aggression is the relative abundance of young males. In this article, we present additional evidence to that effect. The ratio of the number of men ages 15 to 29 years of age versus men 30 and older in a population appears to be associated with the occurrence and severity of conflicts as measured by the number of war casualties. A series of analyses of demographic and war casualty data indicates that the relative prevalence of young men consistently accounts for more than one third of the variance in severity of conflicts.

Human collective aggression: A behavioral ecology perspective

Abstract Moller (1967/68) proposes that the presence of a large number of adolescents and young adults in a population is a precursor of violent conflicts. But acts of collective aggression are typically perpetrated by males, particularly young males between 15 and 30 years of age. This marked sex difference in the degree of participation is found in all human societies, and it has persisted since the beginning of recorded history. Sexually dimorphic behaviors are invariably found in the context of reproduction, and we discuss male coalitional aggression as a reproductive fitness-enhancing social behavior. This type of social behavior may not increase the welfare of an entire population but it is likely to promote the fitness of the coalition participants. This study argues that the age composition of the male population should be regarded as the critical ecological/demographic factor affecting a populations tendency toward peace or violent conflicts. Our analyses of interstate and intrastate episodes of collective aggression since the 1960s indicate the existence of a consistent correlation between the ratio of males 15 to 29 years of age per 100 males 30 years of age and older, and the level of coalitional aggression as measured by the number of reported conflict related deaths.

Development of carbohydrate preference during water rationing: a specific hunger?

Abstract Weanling rats maintained on a water restricted schedule increased their preference for a high-carbohydrate diet versus an isocaloric high-protein diet over a period of six days. This preference disappeared immediately following a period of ad lib water access. In the second experiment rats that had been water restricted prior to their exposure to the test diets developed a clear carbohydrate preference within six hours of exposure. Moreover, the preference was closely linked to the short-term availability of water. Experiment 3 demonstrated that partially desalivated rats preferred high-carbohydrate diets even with ad lib access to water. These results indicated that dry mouth alone is sufficient to produce the dietary selection observed in Experiments 1 and 2 and a specific hunger need not be hypothesized to explain the phenomenon.

Personality and potential conceptions: mating success in a modern Western male sample

Abstract This study tests an evolution-based model of personality by observing the relationship between a constellation of personality traits and mating success in a modern male sample. Mating success, a frequent contributor to Darwinian fitness, was measured via Potential Conceptions Index (Perusse, D. 1993. Cultural and reproductive success in industrial societies: testing the relationship at the proximate and ultimate levels. Behavioral and Brain Sciences , 16 , 267–322). One-hundred and six primarily undergraduate males between ages 18 and 40 were administered a test battery consisting of 18 subscales from seven personality instruments and a sexual experience questionnaire. Bivariate correlation and multiple regression analyses supported study hypotheses by demonstrating mating success to be variously associated with Hypermasculinity Inventory Machismo, Balanced Inventory of Desirable Responding Self-Deception, Sensation Seeking Scale Form V, 10-item Machiavellianism and Multidimensional Sexuality Questionnaire Sexual-Esteem. The possibility is suggested that sexual selection has contributed to the evolution and maintenance of these personality traits in ancestral populations.

Electroconvulsive shock induced impairment and enhancement of a learned escape response

Abstract Rats were given single or multiple ECS treatment 5 min, 30 min, 1, 3, 5, 7, 14 or 31 days following shock escape training in a Y-maze and retested 24 hr later. Both single and multiple ECS induced performance loss if administered 7 or 14 days following training. However, only multiple ECSs induced performance decrement when administered 5 or 30 min after training. Retest performance was facilitated by single or multiple ECSs administered 31 days after training. No significant performance changes were evident following other training-treatment intervals. Physostigmine (anticholinesterase) injection prior to retest augmented the effect of a single ECS producing a pattern of performance alteration resembling that found to result from multiple ECSs. Scopolamine (anticholinergic) eliminated the effects of a single ECS.

Effects of catecholamine agonist and antagonist drugs on acute stomach ulceration induced by medial hypothalamic lesions in rats

In order to investigate the involvement of catecholamines (CAs) in acute stomach ulceration induced by hypothalamic lesions, rats were given bilateral electrolytic anodal lesions in the medial hypothalamus followed by a single subcutaneous injection of CA agonist or antagonist drugs. As in previous studies, lesioned rats that received no post operative drug treatment showed extensive gastric damage when examined 24 hr after the brain lesion. Chlorpromazine, amphetamine, desipramine and isoproterenol caused significant reductions in the extent (total length) and/or number of erosions induced by the brain lesion. Haloperidol and propranolol did not seem to affect ulcer formation. Clozapine increased the number but not the total length of ulcers. Phentolamine, alone or in combination with propranolol, significantly increased both the number and total length of lesion-induced ulcers. Similarities between these results and those reported for most of these drugs in the context of ulcers induced by various experimental stress procedures suggest a degree of commonality between acute stress ulcers and ulcers induced by hypothalamic lesions. The overall pattern of results obtained is also consistent with evidence indicating a protective role for catecholamines in acute ulcer formation.

Development of acute feeding disorders, hyperactivity, and stomach pathology after medial and lateral hypothalamic lesions in rats

The acute effects of medial (VMH) and lateral (LH) hypothalamic lesions on stomach morphology, motor activity, and feeding behavior were compared in two experiments. Rats received VMH or LH lesions and were sacrificed 4, 8, or 24 h later. Both lesions produced high activity counts at 4 h and a comparable number of ulcers, starting at the earliest interval tested. Neither VMH nor LH lesions produced acute changes in other organs, such as the adrenals, thymus, or spleen. In a second experiment, quantitative measures of stomach pathology did not indicate significant differences between ulceration produced by VMH and LH lesions in 24 h. A separate group receiving VMH lesions showed pronounced hyperphagia and hyperdipsia immediately after the lesion, while LH rats were aphagic and adipsic. Motor activity levels after the lesions correlated positively with ulcer incidence and severity. Possible relations between these acute behavioral and visceral effects of hypothalamic lesions are discussed.

Neural and Pavlovian influences on immunity

The traditional view that the nervous and immune systems are functionally independent (aside from general stress effects and autoimmune disorders of the nervous system) is being challenged by a new view that the nervous system regulates the activity of the immune system. If this is true, it should be possible to change the activity of the immune system by means of Pavlovian conditioning, just as it is possible to condition other physiological events influenced by the autonomic nervous system or neuroendocrine substances. Evidence for autonomic and neuroendocrine modulation of immune activity is briefly reviewed; and, the various studies reporting conditioned immune effects, the physiological mechanisms most likely involved, and their possible significance are discussed.

Acute hyperkinesia after hypothalamic lesions: A comparison of the time course, level, and type of hyperkinesia induced by ventromedial and lateral hypothalamic lesions in rats

Abstract Postoperative hyperkinesia induced by ventromedial (VMH) and lateral hypothalamic (LH) lesions was compared in two experiments. In the first experiment overall motility of the animals was monitored continuously for 20 h after the lesions. Both LH and VMH lesions were found to cause comparably high levels of activity in the first 10 h after the lesion. In the next 10 h VMH rats were more active than LH rats. In a second experiment a detailed analysis of the behaviors displayed by rats with VMH or LH lesions at 4, 8, and 24 h after the lesions revealed that different behavioral components contributed to the overall hyperactivity in the two cases, with a predominance of locomotion, rearing, jumping, and gnawing for VMH lesion rats, and rearing, rotations, and forelimb movements for LH lesion rats during the acute hyperactivity stage. These results indicated that acute motor effects of hypothalamic lesions are specific to lesion placement. Relations to other types of hyperkinesia and possible mechanisms involved are discussed.

Ventromedial hypothalamic lesions and stomach ulcers: reduction by non-nutritive bulk ingested in the post lesion period.

Abstract The effects of some dietary properties on stomach ulceration resulting from ventromedial hypothalamic (VMH) brain lesions, were investigated in two experiments. In the first experiment two groups of rats received VMH lesions and one group received sham lesions. One of the lesioned groups was deprived of food and water during the 24 hr post lesion period, as was the sham lesioned group. The other lesioned group was given access to a highly palatable diet and water during the post lesion period. No stomach ulcers were found in the sham lesioned rats. The VMH lesioned group with access to food and water had less glandular stomach ulceration 24 hr after the lesion procedure than the VMH lesioned deprived group (p