A comparison of response patterns on fixed-, variable-, and random-ratio schedules

The behavior of individual pigeons on fixed-ratio, variable-ratio, and random-ratio schedules was examined. Within each type of ratio schedule the size of the ratio was varied in an irregular sequence. At various ratio sizes (5, 10, 40, 80) no differences were found among overall response rates (postreinforcement pause plus running response rate) as a function of ratio type. This similarity in overall response rates held despite noticeable differences in the microstructure of performance both within and across subjects; the primary performance difference on the three types of ratio schedules was the relatively longer postreinforcement pause duration on the fixed-ratio schedule. We concluded that the gross temporal characteristics of performance determined by the relative weightings of the postreinforcement pause and running response rate were primarily controlled by the type of ratio schedule (fixed, variable, or random), whereas the overall rate of responding was controlled by the size of the ratio.     

Choice, relative reinforcer duration, and the changeover ratio

Relative reinforcer duration was varied in concurrent schedules with a fixed-ratio four changeover requirement. The schedule in effect after each reinforcer was randomly chosen. For all three pigeons, relative response rates overmatched relative reinforcer durations. Time allocation was less extreme and, on the average, matched relative reinforcer duration. In a subsequent manipulation, the level of preference was shown to depend on the size of the changeover requirement. These results are similar to those from related unequal reinforcement-frequency procedures.     

Power of the likelihood ratio test in covariance structure analysis

A procedure for computing the power of the likelihood ratio test used in the context of covariance structure analysis is derived. The procedure uses statistics associated with the standard output of the computer programs commonly used and assumes that a specific alternative value of the parameter vector is specified. Using the noncentral Chi-square distribution, the power of the test is approximated by the asymptotic one for a sequence of local alternatives. The procedure is illustrated by an example. A Monte Carlo experiment also shows how good the approximation is for a specific case.This research was made possible by a grant from the Dutch Organization for Advancement of Pure Research (ZWO). The authors also like to acknowledge the helpful comments and suggestions from the editor and anonymous reviewers.     

不同性别比和童年经济状况对未婚男性性态度的影响

基于进化心理学的生命史理论,通过两个实验探讨性别比和童年经济状况同男性性态度间的关系。实验1和实验2分别采用图片和文字材料启动被试的性别比感知,结果发现感知性别比和童年经济状况对未婚男性的"随意性行为"态度表现出显著的交互效应：童年家庭经济状况差的未婚男性在感知到周围女性数量相对充裕的情境下,其性开放态度会较感知到周围男性数量充裕时明显上升;童年家庭富裕的男性的性开放态度在不同感知性别比下保持相对稳定。     

Beyond the breakpoint: reinstatement,renewal, and resurgence of ratio‐strained behavior

Three experiments were conducted using pigeons to assess the recurrence of responding eliminated by increasing the value of a progressive‐ratio schedule to the breakpoint of responding. The procedures used in these assessments were, in successive experiments, reinstatement, renewal and resurgence. Each was effective in returning temporarily the eliminated responding. Reinstatement occurred with both yoked‐time and fixed‐time food deliveries. Both renewal and resurgence resulted in immediate recurrence of the response, and, as in other experiments investigating resurgence, the key peck response resurged as the alternative response extinguished. The results of all three experiments suggest the generality of these recurrence procedures to responding under progressive‐ratio schedules, indicating that strained performance under these schedules is amenable to recovery under the investigated conditions.     

Reinforcer control and human signal-detection performance

Eight humans participated in a two-choice signal-detection task in which stimulus disparity was varied over four levels. Two procedures arranged asymmetrical numbers of reinforcers received for correct left- and right-key responses (the reinforcer ratio). The controlled procedure ensured that the obtained reinforcer ratio remained constant over changes in stimulus disparity, irrespective of subjects' performances. In the uncontrolled procedure, the asymmetrical reinforcer ratio could covary with subjects' performances. The receiver operating characteristic (ROC) patterns obtained from the controlled procedure approximated isobias functions predicted by criterion location measures of bias. The uncontrolled procedure produced variable ROC patterns that were somewhat like the isobias predictions made by likelihood ratio measures of bias; however, the obtained reinforcer ratio became more extreme as discriminability decreased. The obtained pattern of bias was directly related to the obtained reinforcer ratio. This research indicates that criterion location measures seem to be preferable indices of response bias.     

Cultural representations of thinness in women, redux: Playboy magazine's depiction of beauty from 1979 to 1999

Playboy's portrayal of the male ideal of feminine beauty, in terms of overall body size, percent normative weight, and waist-to-hip ratios (WHRs), was analyzed for the years 1979–1999. Trends were examined through body measurements obtained from Playboy centerfolds. Results reveal a continuation of the low body mass index (BMI) found in the Playmates by earlier studies; however, for the 21 years examined, the trend towards increasing thinness seems to have stabilized and may have begun to actually reverse. There was also an increase in the centerfolds’ WHRs over the 21-year time period. Overall, the results support the continued valuing in American society of a thin ideal for women; while the images of beauty have become somewhat heavier over the 21-year period reviewed, the Playmates remain markedly below weights normative for their age group.     

The leg-to-body ratio as a human aesthetic criterion

There are surprisingly few empirical studies on the aesthetic appeal of human legs, examining such variables as length or shape. The human legs are conspicuous in erotic contexts, but few studies have experimentally tested preferences for longer legs. This study examined the utility of the human leg-to-body ratio (LBR) as a specific aesthetic criterion among 71 British undergraduates. Participants rated for physical attractiveness line drawings that varied in five levels of LBR. The results showed that a longer LBR was preferred as maximally attractive in women, whereas a shorter LBR was preferred in men. Evolutionary psychological and socio-cultural explanations for this aesthetic preference are discussed, and the study's limitations are considered.     

Effects of cocaine on performance under fixed-interval schedules with a small tandem ratio requirement

Daily administration of cocaine often results in the development of tolerance to its effects on responding maintained by fixed-ratio schedules. Such effects have been observed to be greater when the ratio value is small, whereas less or no tolerance has been observed at large ratio values. Similar schedule-parameter-dependent tolerance, however, has not been observed with fixed-interval schedules arranging comparable interreinforcement intervals. This experiment examined the possibility that differences in rate and temporal patterning between the two types of schedule are responsible for the differences in observed patterns of tolerance. Five pigeons were trained to key peck on a three-component multiple (tandem fixed-interval fixed-ratio) schedule. The interval values were 10, 30, and 120 s; the tandem ratio was held constant at five responses. Performance appeared more like that observed under fixed-ratio schedules than fixed-interval schedules. Effects of various doses of cocaine given weekly were then determined for each pigeon. A dose that reduced responding was administered prior to each session for 50 days. A reassessment of effects of the range of doses revealed tolerance. The degree of tolerance was similar across components of the multiple schedule. Next, the saline vehicle was administered prior to each session for 50 days to assess the persistence of tolerance. Tolerance diminished in all subjects. Overall, the results suggested that schedule-parameter-dependent tolerance does not depend on the temporal pattern of responding engendered by fixed-ratio schedules.     

Effects of reinforcer probability, delay, and response requirements on the choices of rats and pigeons: possible species differences

In Experiment 1 with rats, a left lever press led to a 5-s delay and then a possible reinforcer. A right lever press led to an adjusting delay and then a certain reinforcer. This delay was adjusted over trials to estimate an indifference point, or a delay at which the two alternatives were chosen about equally often. Indifference points increased as the probability of reinforcement for the left lever decreased. In some conditions with a 20% chance of food, a light above the left lever was lit during the 5-s delay on all trials, but in other conditions, the light was only lit on those trials that ended with food. Unlike previous results with pigeons, the presence or absence of the delay light on no-food trials had no effect on the rats' indifference points. In other conditions, the rats showed less preference for the 20% alternative when the time between trials was longer. In Experiment 2 with rats, fixed-interval schedules were used instead of simple delays, and the presence or absence of the fixed-interval requirement on no-food trials had no effect on the indifference points. In Experiment 3 with rats and Experiment 4 with pigeons, the animals chose between a fixed-ratio 8 schedule that led to food on 33% of the trials and an adjusting-ratio schedule with food on 100% of the trials. Surprisingly, the rats showed less preference for the 33% alternative in conditions in which the ratio requirement was omitted on no-food trials. For the pigeons, the presence or absence of the ratio requirement on no-food trials had little effect. The results suggest that there may be differences between rats and pigeons in how they respond in choice situations involving delayed and probabilistic reinforcers.