Intensity Of Social Interaction Research Articles

Impact of postnatal blockade of N-methyl-d-aspartate receptors on rat behavior: A search for a new developmental model of schizophrenia

The malfunction of glutamatergic neurotransmission in the neonatal or postnatal periods may be a risk factor for the appearance of neuroanatomical, neurochemical or functional changes that are characteristic of schizophrenia. Thus, the present study was undertaken to investigate whether blockade of N-methyl-d-aspartate (NMDA) receptors in the postnatal period influences rat behavior in tests characterizing schizophrenia-like deficits such as psychomotor agitation, impairments of sensorimotor gating, working memory, and intensity of social interactions. (E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid (CGP 40116), a competitive antagonist of NMDA receptors, was given postnatally (1.25 mg/kg on days 1, 3, 6, 9; 2.5 mg/kg on days 12, 15, 18; and finally 5 mg/kg on day 21, all injections s.c.), and rats were tested at 60 days old. We found that blockade of NMDA receptors in the postnatal period led to an enhancement of exploration, mimicking psychomotor agitation, impairments in sensorimotor gating as measured by a prepulse-evoked inhibition of acoustic startle response, and an impaired working memory, as measured by an increase in the latency to achieve accurate rate of response in the delayed alternation task. Decreases in non-aggressive social interactions and increases in aggressive interactions were also observed. In addition to cognitive deficits typical of schizophrenia, rats treated postnatally with NMDA receptor antagonists also showed higher level of fear exhibited in the elevated plus maze. Thus, the blockade of NMDA receptors in the postnatal period may model deficits that are characteristic of schizophrenia.

Embeddedness and Contractual Relationships in China's Transitional Economy

Interfirm contracts represent common economic relations in the marketplace; they are also deeply embedded in social relations and social institutions. In the context of China's transitional economy, this study examines how three mechanisms—economizing transaction costs, network-based social relations, and institutional links—affect interfirm contractual relationships in (1) the choice of search channels for contractual partners, (2) the formality and provisions in a contract, and (3) the intensity of social interaction in contract implementation. Empirical evidence is drawn from information collected on 877 contracts from 620 firms in two Chinese cities, Beijing and Guangzhou. The authors find distinct roles of social relations, institutional links, and regulatory environments in the initiation of contractual partners and the forms of contracts adopted, whereas transaction-specific factors play a significant role in the intensity of social interaction in contract implementation. These findings suggest the interplay among economic calculativeness, social networks and institutional links, and the complementarity in the underlying theoretical ideas.

Embeddedness and Contractual Relationships in China's Transitional Economy

Interfirm contracts represent common economic relations in the marketplace; they are also deeply embedded in social relations and social institutions. In the context of China's transitional economy, this study examines how three mechanisms-economizing transaction costs, network-based social relations, and institutional links-- affect interfirm contractual relationships in (1) the choice of search channels for contractual partners, (2) the formality and provisions in a contract, and (3) the intensity of social interaction in contract implementation. Empirical evidence is drawn from information collected on 877 contracts from 620 firms in two Chinese cities, Beijing and Guangzhou. The authors find distinct roles of social relations, institutional links, and regulatory environments in the initiation of contractual partners and the forms of contracts adopted, whereas transaction-specific factors play a significant role in the intensity of social interaction in contract implementation. These findings suggest the interplay among economic calculativeness, social networks and institutional links, and the complementarity in the underlying theoretical ideas.

The influence of climate on suicidal behaviour in Italy

A growing number of studies report an asymmetry in the seasonal distribution of suicides, with a peak in the late spring months for both sexes. The aim of this study is to verify if the climate, apart from its seasonal change, exerts a direct influence on suicidal behaviour. To this end, deaths by suicide in 17 Italian towns which all have a meteorologic station have been analyzed, taking into account some climatic indicators. Results of analyses show an unequal distribution of suicides with respect to latitude, with a peak in the North. The distribution of deaths by suicide shows a negative relationship with mean yearly temperature values, max and min, and with sun exposure indicators, and a positive, but less significant relationship with rainfall values. As far as climatic variables considered as a whole are concerned, stepwise regression identifies three relevant factors with significant relationships to suicide rates: humidity grade, rainfall mean, and sunlight exposure. These three climatic indicators explain up to 63% (Adj R 2) of the variance in the distribution of suicide rates for both genders, with sunlight exposure offering the most significant contribution, when regressed on suicide rates via a multiple regression model. Higher suicide rates, therefore, correspond to dry places which are less exposed to the sun. However, the variable which shows the most significant correlation with suicide rates for both sexes is not a climatic one, but the percentage of the population aged 65 and over. The distribution of people at greater biological risk for possible disruption of brain neurochemistry (i.e. older people), therefore, predicts the distribution of suicide rates. Climate contributes to this biological risk by modifying both the responsiveness of the circuits that control mood and behaviour, and also the frequency and intensity of social interaction.

Variability in larval development of the tropical reef fish Pomacentrus amboinensis (Pomacentridae): the parental legacy

The effects of food availability, female size, and social interactions on the quality of Pomacentrus amboinensis larvae at hatching were examined using two field-based experiments. In Experiment 1, food availability and female size significantly influenced size, eye diameter and levels of yolk reserves of larvae at hatching. Small females (47 to 52 mm standard length, SL) whose diets were not supplemented, produced the longest larvae (3.0 ± 0.01 mm total length, TL) with the least yolk reserves (50.1 ± 1.04 μm2). Irrespective of female size, those that received additional food produced larvae with the largest yolk-sacs (large females: 87.60 ± 1.53 μm2; small females: 80.14 ± 1.24 μm2). In Experiment 2, interactions with conspecifics had a greater affect on the somatic development of larvae at hatching than food availability. Increased social interactions resulted in larvae that were ⋍3% longer, with 2% greater head depth, than larvae from females that spawned in isolation on the experimental reefs. Fed females produced larvae with ⋍20% more yolk than larvae from females whose diets were not supplemented. All three factors (food availability, female size, and intensity of social interactions) tested within these experiments vary spatially and temporally among reefs. There is the potential, therefore, for larvae at the onset of the planktonic stage to vary in quality, level of development, and probability of survival.

Behaviour, growth, and intensity of social interaction among fish

Behaviour, growth, and intensity of social interaction among fish

RAPID BEHAVIORAL CHANGES IN MEDAKA (ORYZIAS LATIPES) CAUSED BY SELECTION FOR COMPETITIVE AND NONCOMPETITIVE GROWTH.

Behavior is a major component of growth rate variation in fish, but the genetic relationship between behavior and growth is largely unknown. In particular, it is not known how behavior responds to natural or artificial selection on growth. It has been argued that artificial selection for fast growth in competitive environments might lead to higher levels of overall aggression, and therefore there would be no net gain in assimilation efficiency or growth. The contrary has also been argued. It is not immediately obvious, therefore, whether fish that avoid interacting with conspecifics should grow faster, or whether more aggressive, dominant individuals should grow faster. In the present study, we artificially selected fish on the basis of growth in two environments that differed in the intensity of social interactions. In the high interaction environment (HI), food was provided to excess inside a floating cork ring, which limited access to the food and allowed fish to attempt to monopolize the food supply. In the low interaction environment (LI), an equivalent amount of food was spread over the container's surface. In each social environment, fish were selected within family for fast and for slow growth rate during two generations (G1 and G2 ). The response was measured in the third generation (G3 ) on the directly selected trait (growth) and on a correlated trait (agonistic behavior). The magnitude of the direct response to selection on growth in medaka was directly related to population density, i.e., selection was most effective at high densities. Agonistic behavior was inversely related to growth when individuals were raised and selected in an environment where enforced social interaction took place, so long as food was not limited in quantity.

Ecological Correlates of the Educative Style of Afro-American Children

In the research on the influence of the physical environment of the home on the development of children, factors such as the presence of age-appropriate play materials, the access to physical and visual exploration in the environment, and the amount and intensity of noise stimulation have been found to influence cognitive development associated with educative competence. Other factors include the amount of personal space, temporal regularity, and the type and intensity of social interaction.1 Feuerstein2 asserts that the impact of these factors is dependent upon the experience and intent of the mediating adult who frames, selects, focuses, and interprets the experiences in ways that produce the culturally appropriate educative style. Wachs,3 however, hypothesizes that it is the specific environment interacting with the organismic variables which determines the impact upon the child regardless of the sociocultural mediating experiences. Not included in either view is a theory on whether or not the child develops a

The archaeology of art: excavations at Maidenwell and Gatton Shelters, southeast Queensland

This paper presents the results of excavations at Maidenwell and Gatton Shelters, two rock art sites in S.E. Queensland. The work was undertaken as part of a research project concerned with a major theme in Australian prehistory - the development of social and economic complexity in Aboriginal society (e.g. Lourandos 1983, 1985; Morwood 1984). As foci for a range of symbolic activities, Maidenwell and Gatton Shelters have the potential to yield evidence for changes in the nature and intensity of social interaction, particularly in the context of evidence for economic, technological and demographic change (cf. Conkey 1978, 1980; Gamble 1982, 1983).

Density, habitat, and the mating system of the Western Sandpiper (Calidris mauri).

The hypothesis that intense predation, variable food availability, and increased social interactions in high density populations have been important factors promoting the evolution of polygynous and promiscuous mating systems in certain Calidridine sandpipers (Holmes and Pitelka, 1966) is examined in breeding populations of the Western Sandpiper (Calidris mauri) in subarctic Alaska.Western Sandpipers breed in a habitat consisting of a complex mosaic of wet low-lying marshes and relatively well-drained, heath-covered tundra. They defend small territories and nest on the latter, while some feeding also occurs there. Most foods however are obtained off territory in the wet marshes and along the shores of lakes, rivers and sloughs.Densities in the nesting areas ranged from 132-196 pairs/40 ha at the base of a low range of hills to 200-300/40 ha on hummocks surrounded completely by marsh. These densities, the highest reported for a Calidridine sandpiper, are relatively constant from year to year.The mating system of the Western Sandpiper is monogamous, both sexes incubate and care for young. Correlated with a strong single pair-bond and stable populations is a strong tendency to return to the same site. Of sandpipers marked, an average of 57.6% of males and 48.8% of females returned in succeeding years, frequently to the same territory or its immediate vicinity. Of the pairs returning to the study area in subsequent years, 61.5% reunited.The restriction of nesting activities to heath tundra is considered to be a result of the protection it provides for nests. With the separation of nesting and feeding areas and with relatively abundant food sources that are not significantly affected by weather, a large nesting area is not required, allowing high densities of Western Sandpipers to occupy the patches of heath-covered tundra. In this ecological context, the high intensity of social interactions has not resulted in the evolution of a nonmonogamous mating system. Indeed, the increased protection afforded offspring by the presence of both parents is probably the most important selective force promoting the evolution of the monogamous mating pattern in Western Sandpipers.

Social interaction at a high-rise, high-density urban flat complex

The present study focuses on the social interaction experiences of the residents of Schubart Park, a high-rise, high-density, multi-building flat complex catering for middle-class residents in central Pretoria. The question is posed whether the conclusions of social scientists regarding the supposed negative influence of such complexes are always justified. An answer to the question is attempted by using a theoretical model of density, crowding, privacy, and environmental perception to help interpret the findings. The theoretical model, in which emphasis is placed on social interaction (an important field of interest for the sociologist), is shown to have sociological relevance and is interpreted from a specifically sociological point of view. The present study investigates the frequency, nature, and intensity of social Interaction at Schubart Park on the assumption that associative social interaction can mitigate the negative effects of density and reduce the probability that unacceptable crowding will b...

Reproductive Performance of a Population of Woodchucks after a Change in Sex Ratio

A reciprocal relationship between density and reproductive performance in mammalian populations is now well established (Crew and Mirskaia 1931, Retzlaff 1938, Davis 1951, Calhoun 1952, Christian 1955a, b, and 1956, Christian and LeMunyan 1958, Clark 1955, Kalela 1957, Crowcroft and Rowe 1957, Hoffman 1958, Helmreich 1960). This relationship apparently depends upon social interactions which increase with increased population density and which operate through endocrine mechanisms to affect reproduction (Clhristian 1959). A corollary to this thesis is that actual numbers (density per se) are not wholly determinant. The intensity of social interaction also should be related to factors such as the sex ratio and age composition of a population, because present evidence shows clearly that competitive behavior changes with age and differs with sex. The present paper describes the reproductive performances of 3 different populations of woodchucks (Marmiota m. monax L.). In one population, a surplus of males was maintained by selectively removing a portion of the females at intervals in 1957 and 1958. In a 2nd population, males and females were removed selectively in large numbers in 1957 and 1958 to reduce density and eliminate older animals. The 3rd populatioln was disturbed as little as possible during this time. The reproductive performance of each population was assessed in 1959 by examining the reproductive tracts of females collected during the breeding seasonl. The main purpose of this paper is to describe the way in which each population was man-ipulated and to present an analysis of the reproductive data collected subsequently. Observations oni mortality, movements, and social interactions, and data colncerned with compensatory responses to the