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以1999-2003年生物技术学科期刊文献分布曲线为依据,利用知识密度梯度graduR(n)的概念,对知识场中文献分布特征进行分析。结果表明,在任何一个学科的知识场中,集中区文献分布呈间断性变化,离散区文献分布呈连续性变化,从而构成期刊文献分布的基本特征。基于此,指出期刊文献分布特征研究是对文献分布规律的进一步描述。 相似文献
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Immediately after a recently fed rodentdemonstrator interacts with a conspecificobserver, the observer shows a substantially enhanced preference for whatever food its demonstrator ate. Here we show that (1) influence
of a single, 30-min interaction with a demonstrator on an observer’s food preference lasts for at least 1 month, and (2) observers
interacting on 2 successive days with a demonstrator fed a different diet on each day show significantly enhanced preferences
for both diets a month later. Such enduring effects of single, brief interactions between a demonstrator rat and its observer
provide an efficient means for studying physiological and behavioral substrates of long-term memory in rodents. Together with
the results of previous studies of social influences on food choices of rats, the present results also suggest that rats may
use information acquired from conspecifics to identify both toxic and safe foods for many weeks after they have acquired this
information. 相似文献
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Naive “observer” rats that interact with conspecific “demonstrators” fed a distinctive food increase intake of the food their demonstrators have eaten. Here we found that observer rats that had interacted simultaneously with 2 demonstrator rats, 1 fed a distinctively flavored, protein-poor food, the other a distinctively flavored, protein-rich food, did not prefer the former. Similarly, observer rats ate equal amounts of two distinctively flavored foods after interacting simultaneously with 2 demonstrator rats, 1 that had consumed all food available to it, the other fed from a surplus of the second food. Last, observer rats that had interacted with both a “trustworthy” demonstrator (1 an observer had learned ate only nutritious foods) and an “untrustworthy” demonstrator (1 an observer had learned ate noxious substances) did not prefer unfamiliar foods eaten by trustworthy demonstrators to those eaten by untrustworthy demonstrators. These findings suggest limits on social information observers use in selecting foods. 相似文献
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Bennett G. Galef Brigitte Rudolf Elaine E. Whiskin Elena Choleris Marisa Mainardi Paola Valsecchi 《Learning & behavior》1998,26(4):448-454
In recent experiments in which the social influences on feeding in Mongolian gerbils were investigated, observer gerbils acquired food preferences from conspecific demonstrators only if the demonstrators and observers were either related or familiar. Even then, the effects of demonstrator gerbils on observers’ food choices lasted less than 24 h. In similar experiments with Norway rats, the familiarity/relatedness of demonstrators and observers had little effect on social learning, and the demonstrators’ influence on observers’ food choices lasted many days. We examined the causes of these differences and found that, after observer gerbils interacted with either unfamiliar or familiar conspecific demonstrators that had been fed using procedures typically used to feed demonstrator rats, they showed long-lasting social learning about foods, whereas observer rats interacting with conspecific demonstrators that had been fed as demonstrator gerbils normally are fed showed effects of familiarity/relatedness to demonstrators on their social learning about foods. Procedural differences, rather than species differences, seem to be responsible for reported inconsistencies in social learning about foods by rats and gerbils. 相似文献
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Three experiments were undertaken to examine the effects of interactions with demonstrator rats made ill by injection of lithium chloride (LiCl) on the later food choices of their observers. We found that (1) observer rats that had been taught an aversion to an unfamiliar diet exhibited a substantial reduction of that aversion after interacting with poisoned demonstrators that had eaten the diet to which the observers had learned an aversion, (2) exposure of an observer rat to poisoned demonstrator rats that had eaten a diet interfered with later acquisition by the observer of an aversion to the diet that the poisoned demonstrators had eaten, and (3) after interacting with poisoned demonstrators that had eaten one of two diets, observers that ate both diets and were then made ill formed an aversion to whichever diet their respective, poisoned demonstrators had not eaten. The present experiments, like previous studies both in our laboratory and elsewhere, failed to provide any evidence that naive observer rats will learn to avoid a food as a result of interacting with demonstrator rats that had eaten the food and exhibit symptoms of toxicosis. To the contrary, observer rats in the present experiments exhibited an enhanced preference for foods eaten by sick demonstrators. 相似文献
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We fed demonstrator rats diets made by adding three, four, or five different flavorants to powdered Purina Rat Chow. We then allowed each of these demonstrator rats to interact with a naive observer rat for 30 min. We found that (1) observers exhibited enhanced preferences for many of the individual flavorants in the multiflavored diets that their respective demonstrators had eaten and (2) the probability of an observer exhibiting enhanced preference for an individual flavorant in its demonstrator’s diet decreased as the number of flavorants in that diet increased. In Experiment 2, the individual members of pairs of subjects were each fed one of two different four-flavored diets. The subjects in each pair interacted for 30 min, then each chose between two single-flavored diets. One of these single-flavored diets contained a flavorant in the four-flavored food that a subject had itself eaten; the other single-flavored diet contained a flavorant in the four-flavored diet that a subject’s partner had eaten. The subjects showed enhanced preferences for six of eight flavorants in the four-flavored diets that their respective partners had eaten. 相似文献
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