Brain amine levels and competitive behavior between rats in a straight runway.
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In groups of 39 males and 39 female undergraduates played a reaction-time game in which descriptions of a player's shock settings were constant or consistently below or above another player's; wins were varied. Ratings of aggression, offensiveness, positivity on semantic scales showed naive subjects considered the offensive or defensive nature of obseved behavior in making ratings.
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The present research was designed to test the hypothesis that children would compete more in tetrads than in dyads. Twenty-two pairs of male and 14 pairs of female target children (N = 72) played a competitive game in both tetrads and dyads. Consistent with the hypothesis, male target children competed more in tetrads than in dyads. This hypothesis was not supported for females, however. Analyses of the dynamics of tetrads and dyads further demonstrated that based on a global measure of smiling, the emotional atmosphere was less positive in tetrads than in dyads. The causes and consequences of interaction in different sized social groups are discussed.
Male hooded rats with medial hypothalamic lesions or sham lesions were given tests of defensiveness toward an experimenter. The 8 lesioned males with the highest defensiveness scores and 7 sham-lesioned males were each placed in a double cage with a single intact female. For each pair of rats, food was continuously present but water was available for only 1 hr/day through a single water spout. Beginning on the fifth day of water deprivation, each pair of animals was given a 4-min water competition test on 3 consecutive days. Competition for water was created by placing a plastic ring over the hole in the cage where the water spout entered the cage. The ring restricted access to the spout to a single animal and was put in place 5 min before water was given. One hr following the competition test, each pair of animals was given access to a single unencumbered spout for a 1-hr period. Rats with medial hypothalamic lesions drank significantly more and initiated more aggression than their female cagemates during the 4-min competition tests. Sham-lesioned rats neither drank significantly more nor were more aggressive than their female cagemates. These results are consistent with previous observations indicating that the aggressiveness of rats with medial hypothalamic lesions can be elicited by a competition situation.
Castrated male hooded rats were given electrolytic lesions of the medial hypothalamus or sham lesions. Another group of castrated rats was implanted subcutaneously with bilateral testosterone-filled Silastic capsules or empty capsules. Lesioned animals with a high defensiveness (reactivity) score toward the experimenter were each placed in a cage with a sham-lesioned animal of a similar weight. Animals with testosterone implants were likewise housed with an animal of similar weight without a testosterone implant. Following a period of adaptation to a 23-hr water deprivation schedule, each pair of rats was given daily competition tests on each of 6 days. During the tests, a single water spout was placed in the cage for a 4-min period. The spout was surrounded by a plastic ring which prevented more than one animal from drinking at any time. Access to an unencumbered water spout was present following the competition test for 1-hr each day. Rats with medial hypothalamic lesions displayed more aggression than sham-lesioned rats during the competition tests and were able to spend more time drinking. Rats with testosterone implants were more successful in maintaining access to the spout but did not consistently display more aggression than their cagemates without testosterone implants. The aggression of the lesioned rats was defensive while that of animals with testosterone implants corresponded to intermale social aggression. These results demonstrate that a competitive situation can elicit intermale social aggression mediated by testosterone and defensiveness induced by medial hypothalamic lesions.
Commons-dilemma simulation games are designed to examine behavior associated with preservation and destruction of slowly regenerating natural resources. In Experiment 1, 120 introductory psychology students in the United States were assigned to high- or low-environmental-concern conditions based on a median split of their scores from a pretest. They then played either a points game, in which they selected numerical points from a slowly regenerating pool, or a tree game, in which they harvested trees from a jointly managed forest. After the game, subjects were asked to sign a petition for an environmental cause, to participate in a litter pick-up, and to participate in a recycling drive. Neither environmental concern nor proenvironmental behaviors were related to commons dilemma performance. In Experiment 2, 57 other introductory psychology students were assessed on environmental concern and Machiavellian personality, size of other players' harvesting choices, and other players' altruistic choices, all correlated with subjects' outcomes in the game. Overall, cooperation and competition were more important than environmental concern in predicting behavior in the commons dilemma simulation game.
Are health maintenance organizations (HMOs) less profitable in more competitive markets, and does competition erode unusually high profits over time? To answer these questions, we examined profit rates (as a proportion of revenues) in 1994 and 1997 for all HMOs in 259 metropolitan areas. We found that profits were significantly lower on average in 1994 in markets with more competition, measured alternatively by the number of HMOs or their market concentration. We also found that there was no relationship between a market's relative profit ranking in 1994 and its ranking in 1997; highly profitable markets were not able to preserve their relative standing. Neither the proportion of HMO enrollees in for-profit HMOs nor HMO market penetration was significantly related to profit rates.
Observation about cohabitation among B. glabrata and B. tenagophila revealed a greater vulnerability of B. tenagophila population during the process of competition when its density was severely decreased in 12 trials, moderate in 2 trials. It was higher than B. glabrata in only one trial. Some snail water chemical parameters analysed such as pH, alkalinity, conductivity and oxygen dissolved, and the viability rate of batch of eggs didn't give subsidy to explain the competition mechanism. The newly-born survival, in the situation of cohabitation, was low for both species. This reveals the existence of intra and interspecific competitive interaction. The fertility rate reduction of B. tenagophila during the cohabitation was considered as a cause of its exclusion. One of the factors that seems to have influenced the fertility rate was a possible wrong crossing.
Rats pressing a lever for food reinforcement showed large positive-contrast effects when provided with the opportunity for a competing wheel-running response. Positive and negative behavioral contrast may reflect reallocation of competing interim and terminal responses between schedule components following changes in the reinforcement conditions in one component.
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that binds and mediates responses to many halogenated aromatic compounds (HACs). Exposure to mixtures of HACs frequently results in nonadditive behavior in both in vivo and in vitro assays. One cause is antagonism, which results when two or more ligands compete for a limited supply of the AhR; one interacts agonistically to induce a strong response, and the other interacts unproductively, eliciting little or no response. This study involves the mechanism by which HACs induce CYP 1A1. Agonistic (e.g., TCDD) and unproductive (e.g., PCB 153) HACs behaved similarly through the stages of initial AhR binding and conversion of the initial AhR-ligand complex to the form that possesses increased affinity for the bound ligand. They diverged in the ability of the AhR-HAC complex to bind to a synthetic oligonucleotide containing the consensus dioxin response enhancer sequence, as studied by the gel retardation assay. Competition for the Ah receptor was used to explain antagonistic behavior between TCDD and other HACs in both the gel retardation assay and the downstream response of CYP 1A1 induction in primary rat hepatocytes.
To study the interaction between cocultured Listeria monocytogenes and an antagonistic Leuconostoc strain producing an anti-Listeria bacteriocin, flow cytometry, a technique allowing on-line and real-time analysis, was used along with classical microbiological methods. Culture methods and flow cytometric measurements of the mixed culture over time point to a bactericidal action of the lactic acid-producing bacterial strain against L. monocytogenes cells.
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Spectator behavior in competition is analyzed in terms of spectators' response (positive or negative), or lack of response in reaction to a player's action, or which is independent of a player's action, in a home or away game. This study investigated the perceived contribution of these variables to extreme psychological arousal states (crisis, noncrisis). Forty-eight elite ball-game players responded to a questionnaire asking them to estimate the occurrence probability of the Bayesian combinations among these variables under crisis and noncrisis conditions. An RM-ANOVA procedure revealed that under the crisis condition a negative response, an unsuccessful action, and a home game were rated as more probable, whereas under the noncrisis condition the reverse would be true. The athlete's psychological state was more strongly related to spectator response than to game location or athlete's action. Results are discussed theoretically in reference to the crisis construct.
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Prior research with children and nonhuman animals suggests that females engage in interference competition, in which I individual reduces another's chances of gaining access to a resource, only when resources are scarce, whereas males use it more widely. This study was designed to compare males' and females' use of interference competition in games in which resources were scarce or plentiful. Forty groups of 4 same-sex children from kindergarten or Grade 4 played the 2 games on 2 days. Grade 4 girls used less interference competition when resources were plentiful than when they were scarce. Results are useful for generating a contextually based model of the development of sex differences in competitive behavior.
In the first two experiments, subjects' choices to earn points (exchangeable for money) either by competing with a fictitious opponent or by not competing were studied. Buskist, Barry, Morgan, and Rossi's (1984) competitive fixed-interval schedule was modified to include a second response option, a noncompetitive fixed-interval schedule. After choosing to enter either option, the opportunity for reinforcers became available after the fixed-interval's duration had elapsed. Under the no-competition condition, points were always available after the interval had elapsed. Under the competition condition, points were available based on a predetermined probability of delivery. Experiments 1 and 2 examined how reinforcer probabilities and reinforcer magnitudes affected subjects' choices to compete. Several general conclusions can be made about the results: (a) Strong preferences to compete were observed at high and moderate reinforcer probabilities; (b) competing was observed even at very low reinforcer probabilities; (c) response rates were always higher in the competition component than in the no-competition component; and (d) response rates and choices to compete were insensitive to reinforcer-magnitude manipulations. In Experiment 3, the social context of this choice schedule was removed to determine whether the high levels of competing observed in the first two experiments were due to a response preference engendered by the social context provided by the experimenters through instructions. In contrast to the first two experiments, these subjects preferred the 60-s fixed-interval schedule (formerly the no-competition option), indicating that the instructions themselves were responsible for the preference to compete. This choice paradigm may be useful to future researchers interested in the effects of other independent variables (e.g., drugs, social context, instructions) on competitive behavior.