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511.
Two important cues to female physical attractiveness are body mass index (BMI) and body shape as measured by the waist-to-hip ratio (WHR). This study examined the relative contribution of both cues in three culturally distinct populations. A total of 119 Finnish, Sámi and British male observers rated a set of un-edited photographs of women with known BMI and WHR. The results showed that there were significant differences in preferences for physical attractiveness, with the indigenous Sámi preferring figures with larger BMIs and more tolerant of heavyweight figures than either Finnish participants in Helsinki or Britons in London, who were indistinguishable in their preferences for slim figures. The findings are discussed in terms of evolutionary psychological explanations of mate selection, and sociocultural theories which emphasizes the learning of preferences for body sizes in social and cultural contexts. 相似文献
512.
Alexander J. Mussap 《Sex roles》2007,56(1-2):33-43
The role of waist-to-hip ratio (WHR) in unhealthy body change was examined in a sample of 143 women university students. They
completed the Eating Disorder Examination-Questionnaire (EDE-Q), reported their level of concern with weight and with WHR,
and used unmarked measuring tapes to record their subjective (self-perceived), ideal, and objective (measured) waist and hip circumference.
Although body shape was reported as important, and concern with WHR correlated significantly with symptoms of disordered eating,
the relationships involving WHR were not independent of those involving body weight. Thus, there appears to be little behavioural
and/or clinical significance in the aesthetic evaluations made by women of their WHR. Reasons for this are considered in light
of evidence that women regard WHR as more difficult to control and less amenable to change than their overall body weight. 相似文献
513.
The performance of all five students in an adjustment class for deaf children was compared under fixed and variable ratio schedules of reinforcement. During the fixed ratio (FR) condition, students earned checks if they were attentive and did not engage in disruptive behavior. These checks could be exchanged for the opportunity to draw a prize from a grab bag. During the variable ratio (VR) condition, they earned a draw from the grab bag according to a variable ratio schedule with a mean ratio equal to the value of the preceding FR schedule. During the VR condition, students visually attended more and engaged in disruptive behavior less often than during the FR condition. The number of math problems completed per minute was also higher during the VR condition although no specific consequences were applied to math performance. 相似文献
514.
Schwartz B 《Journal of the experimental analysis of behavior》1977,27(2):301-313
The duration of pigeons' key pecks was studied in three experiments. Experiment I revealed that key pecks early in exposure to continuous reinforcement were of short duration, as were key pecks observed on an omission procedure in which pecks prevented food delivery. Key pecks later in exposure to continuous reinforcement, and those that occurred on positive automaintenance procedures, were of long duration. In Experiment II, pigeons were exposed to fixed-interval and fixed-ratio reinforcement schedules, and durations were recorded separately for each quarter of each interval or ratio. On fixed interval, durations were shorter in the first quarter of each interval than in subsequent quarters; on fixed ratio, durations were longer in the first quarter of the ratio than in subsequent quarters. These data parallel observations of concurrent operant responding and salivation in dogs. In Experiment III, pigeons were exposed to a discrete trial, differential-reinforcement-of-low-rate 6-sec schedule. Durations of responses in the first 2 sec of the trial were substantially shorter than those of responses that occurred later. The data from all three experiments support the view that the pigeon's "key peck" actually consists of two subclasses of peck, one reflexive and one operant. 相似文献
515.
Performance of children under a multiple random-ratio random-interval schedule of reinforcement 下载免费PDF全文
Three children, aged 1.5, 2.5, and 4.5 years, pressed telegraph keys under a two-component multiple random-ratio random-interval schedule of reinforcement. In the first condition, responses on the left key were reinforced under a random-interval schedule and responses on the right key were reinforced under a random-ratio schedule. In the second condition, the schedule components were reversed. In the third condition, the original arrangement was reinstated. For all subjects, rates of responding were higher in the random-ratio component despite higher rates of reinforcement in the random-interval component. The average interreinforcement interval of the random-interval component was increased in the fourth condition, resulting in more similar rates of reinforcement for both schedule components, and then returned to its original value in the fifth condition. In both conditions, all subjects continued to exhibit higher rates of responding in the ratio component than in the interval component. Although these observations are consistent with results from studies with pigeons, it is argued that the response-rate differences between the interval and ratio schedule components are sufficient to demonstrate schedule sensitivity. 相似文献
516.
Excessive defecation, typically considered to be a concomitant of stress, was experimentally induced or eliminated under specific schedules of positive reinforcement of lever pressing by rats. The schedules were, by and large, those under which polydipsia is typically induced. In the first of three experiments, rats under fixed-interval 32-second schedules and variable interval 32-second schedules for food and water reinforcers defecated profusely, but not under fixed-interval one-second schedules or other small interval schedules. Somewhat higher rates of defecation were observed on variable interval 32-second schedules than on fixed-interval 32-second schedules. In a second experiment, fixed-ratio schedules were used, some of which resulted in responding such that reinforcement densities were similar to those on the interval schedules that induced defecation. Defecation was not systematically induced by these ratio schedules. In a third experiment, fixed-time schedules of food presentations were utilized. High rates of defecation were induced comparable to those induced by interval schedules of the same time parameter. No other behavior commonly termed "emotional" was observed in any of these experiments. 相似文献
517.
518.
植入前遗传学诊断中性别选择的伦理辩护 总被引:1,自引:0,他引:1
植入前遗传学诊断(PGD)是在胚胎植入子宫前进行遗传学检查的新技术。它可对植入胚胎进行性别选择,从而引发了会增加我国出生人口性别比的担忧。通过对PGD性别选择伦理风险的分析,指出其用于医学需要时不会对性别比造成危害。但在实施过程中需要医生、患者及社会全体人员共同参与,避免该技术用于非医学目的的需要。 相似文献
519.
In this paper, we propose a cluster-MDS model for two-way one-mode continuous rating dissimilarity data. The model aims at
partitioning the objects into classes and simultaneously representing the cluster centers in a low-dimensional space. Under
the normal distribution assumption, a latent class model is developed in terms of the set of dissimilarities in a maximum
likelihood framework. In each iteration, the probability that a dissimilarity belongs to each of the blocks conforming to
a partition of the original dissimilarity matrix, and the rest of parameters, are estimated in a simulated annealing based
algorithm. A model selection strategy is used to test the number of latent classes and the dimensionality of the problem.
Both simulated and classical dissimilarity data are analyzed to illustrate the model. 相似文献
520.
Richard A. Chechile 《Journal of mathematical psychology》2009,53(6):562-576
For a study with multinomial data where there are ng individuals and with each person having nr test trials, the question arises as to how to fit the parameters of a multinomial processing tree (MPT) model. Should each parameter be estimated for each individual and then averaged to obtain a group estimate, or should the frequencies in the multinomial categories be pooled so that the model is fit once for the entire group? This basic question is explored with a series of Monte Carlo simulations for some prototypical MPT models. There is a general finding of a pooling advantage for the case where there is a single experimental condition. Also when there are different experimental conditions, there is reduced bias for detecting condition differences for a method based on the pooled data. Although the focus of the paper is on multinomial models, a general theorem is advanced that establishes a basic condition that determines whether there is or is not a difference between the averaging of individual estimates and the estimate based on the pooled data. 相似文献