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1.
According to scalar expectancy theory (SET), instrumental performance is determined by the ratio of the time between reinforcements in the trial (T T) to the overall time between reinforcements (T O). Groups for which theT O|T T ratio is the same should perform similarly. According to the sequential-memory view, the memory of nonreward becomes a signal for reward, and thereby promotes strong responding, when that memory is retrieved on a reward trial. In each of three runway investigations employing rats in a runway, two groups were compared that had the sameT O |T T ratio but that differed in the tendency to retrieve the memory of nonreward on a rewarded trial. In each investigation faster running on critical nonrewarded trials was associated with the group having the stronger tendency to retrieve the memory of nonreward on a rewarded trial. These findings are consistent with the predictions of the sequential-memory view, as well as with certain earlier findings, but are inconsistent with SET. It was indicated that the groups compared here were matched along a considerable number of dimensions—an unprecedented number for a varied reward investigation. 相似文献
2.
In matching-to-sample, comparison choice should be controlled by the identity of the sample and, when the sample is not available,
by the overall probability of reinforcement associated with each of the comparisons. In the present research, pigeons were
trained to match a frequent sample (appearing on 80% of the trials) to one comparison (C
fr) and an infrequent sample (appearing on 20% of the trials) to the other (C
inf), with the number of reinforcements associated with each sample equated. In Experiment 1, the task was identity matching;
in Experiments 2 and 3, it was symbolic matching. We asked whether, when control of comparison choice by the sample was reduced
(by inserting a delay between the sample and the comparisons), pigeons would choose comparisons on the basis of (1) the number
of reinforcements per comparison (and thus show no comparison bias), (2) the comparison associated with the more frequent
sample during training (and show a preference forC
fr), or (3) the probability of reinforcement given a correct response (and show a preference forC
inf), or (4) inhibition produced by nonreinforced choice of the more frequently correct comparison (and show a preference forC
inf). Pigeons showed a significant tendency to chooseC
fr. In Experiment 3, we showed that this bias did not result from the effects of intertrial facilitation or interference. Thus,
it appears that when control of comparison choice by the sample is reduced, pigeons’ choice is controlled not merely by the
probability of reinforcement but also by overall sample frequency. 相似文献
3.
Two experiments were performed to investigate the relationship between excitatory stimulus control (number of responses to a training stimulus) and dimensional stimulus control (generalization gradient slope). In experiment 1, after being trained to peck a green key, pigeons received either 20, 40, or 80 brief (.5, 2, 4, or 8 sec) presentations of a 45-deg line followed by reinforcement (12 groups) or 20, 40, or 80 reinforcements for pecking a continuously presented 45-deg line (3 groups). Number of reinforcements determined the slope (percent of total responses to 45 deg) of a subsequent line-angle generalization gradient, but number of responses to the 45-deg line in the test was controlled by total experience with 45 deg as measured by either total exposure time or total responses to 45 deg in training. In a second experiment, it was shown that increasing the number of days of pretraining to green decreased the slope of the gradient (in subjects given 2-sec presentations), but had no effect on number of responses to 45 deg in the test. Furthermore, continuous presentation yielded flatter gradients but more responding to the 45-deg line in the test than did 2-sec presentations. It was concluded that the measures of dimensional stimulus control and excitatory stimulus control reflect different processes because they vary differentially (sometimes in different directions) in response to the same independent variable manipulations. 相似文献
4.
Five groups of pigeons were studied in an auto-shaping procedure which programmed two types of trials represented by hues on the response key. Each signal was separated by a brief intertriai interval. Three groups were studied with a positive correlation between one of the signals and food (contingent groups). They differed with respect to the frequency with which the positive signal appeared. Two noncontingent groups were studied in which the correlation between the signals and food was eliminated by programming food with the same probability following either signal. One noncontingent group had a high density of reinforcement produced by adding reinforcement in the other signal, at the same rate as programmed in the positive signal for the contingent groups. The other noncontingent group experienced the same number of reinforcements in the session as the contingent group with the least frequent positive trial, but these reinforcements were distributed with equal probability across the signals. Birds in the contingent groups with intermediate or infrequent positive signals all acquired reliable pecking, with acquisition most rapid for the infrequent signal. Maintained responding covaried with the speed of acquisition. No birds in the noncontingent groups showed reliable responding. Birds in the contingent group with a frequent positive signal (approximately 3/4 of the session), also showed no reliable pecking. This result suggests that more than one noncontingent group is informative for assessing the role of differential reinforcement probability in the acquisition of auto-shaped keypecking. In particular, a noncontingent group which controls for the frequency of reinforced trials is an appropriate reference group.
相似文献5.
为减缓由于碳纤维与碳化硅基体热膨胀系数差异导致的微裂纹的产生,同时采用了C、SiC纤维作为增强体,通过有机前驱体浸渍裂解法(PIP)制备了(C-SiC)f/SiC复合材料,并通过扫描电子显微镜对复合材料的显微结构进行了分析,研究了复合材料中纤维排布方式以及基体相组成。研究发现,采用扫描电子显微镜的方法能够清晰地分辨出复合材料中各相的存在形式。从复合材料抛光面分析可以发现,在纤维束交错处存在束间基体聚集区域。复合材料基体主要由具有不同衬度的两相组成,分别是由含纳米SiC粉体浆料裂解产物和有机聚合物前驱体(PCS)裂解产物。PCS裂解产物主要呈带状,分布在浆料裂解过程中形成的裂纹和微孔中。 相似文献
6.
We trained 4 pigeons in a numerical bisection task to discriminate between pairs of keylight flashes with a ratio of 1∶3 (2
vs. 6, 4 vs. 12, and 8 vs. 24) that were presented in a sample phase. Responses to the blue key were reinforced after a sequence
of a larger number of flashes, and responses to the white key were reinforced after a sequence of a smaller number of flashes.
The intervals between flashes in the sample phase were randomized to attenuate the covariation of temporal cues with flash
number. Pigeons responded accurately in each of the discriminations, with typically 85%–90% correct responses. Transfer tests
showed that the proportion of large responses increased with number and performance generalized to larger values outside the training ranges. Psychometric functions
superposed when plotted on a relative scale, and estimates of Weber fractions were approximately constant, suggesting that
variability was scalar. However, contrary to previous research in nonhumans, bisection points were located at the arithmetic,
not geometric, mean. Hierarchical logistic regressions confirmed significant control over responding by number beyond that
attributable to temporal cues. These results show that pigeons are able to respond accurately in a relative numerosity discrimination
with successively presented visual stimuli, although the nature of the numerical representation and response rule remains
unclear. 相似文献
7.
8.
Numerical competence has been studied in animals under a variety of conditions, but only a few experiments have reported animals’
ability to detect absolute number. Capaldi and Miller (1988) tested rats’ ability to detect absolute number by using biologically
important events—the number of reinforced runs followed by a nonreinforced run—and found that the rats ran significantly slower
on the nonreinforced run. In the present experiments, we used a similar procedure. Pigeons were given a sequence of trials
in which responding on the first three trials ended in reinforcement but responding on the fourth trial did not (RRRN). When
the response requirement on each trial was a single peck (Experiment 1), we found no significant increase in latency to peck
on the fourth trial. When the response requirement was increased to 10 pecks (Experiment 2), however, the time to complete
the peck requirement was significantly longer on the nonreinforced trial than on the reinforced trials. Tests for control
by time, number of responses, and amount of food consumed indicated that the pigeons were using primarily the number of reinforcements
obtained in each sequence as a cue for nonreinforcement. This procedure represents a sensitive and efficient method for studying
numerical competence in animals. 相似文献
9.
Two accounts of how density of reinforcement affects steady-state performance on probabilistic schedules were compared: the real-time linear operator (RTLO) model and a temporal control model (in which response strength is determined by reinforcement probability as a function of postreinforcement time). In Experiment 1, the probability of reinforcement repeatedly cycled between extinction and a random-ratio 10 schedule. Response-rate gain and phase did not change with period of the cycle as predicted by the RTLO model, nor did either model predict the differences in response rate following reinforcement at different points in the cycle. In Experiment 2, the probability of reinforcement was elevated immediately following a reinforcement but fell after a few seconds. Previous reinforcements had no effect upon responding. An extension of the temporal control model, the cumulative impulse model, allowed for the summing of response strength over successive reinforcements and was consistent with the data of both experiments. 相似文献
10.
In three experiments, we examined the effects of signaling reinforcement during operant responding in order to illuminate the factors underlying instrumental overshadowing and potentiation effects. Specifically, we examined whether signaling reinforcement produces an enhancement and attentuation of responding when the response-reinforcer correlation is weak and strong, respectively. In Experiment 1, rats responded on variable-ratio (VR) or variable-interval (VI) schedules that were equated for the number of responses emitted per reinforcer. A signal correlated with reinforcement enhanced response rates on the VR schedule, but attenuated response rates were produced by the signal on the VI schedule. In Experiment 2, two groups of rats responded on a VI schedule while the two other groups received a conjoint VI, negative fixed-ratio schedule in which the subjects lost the availability of reinforcements if they emitted high response rates. A reinforcement signal attenuated responding for the simple VI groups but not for the animals given the negative fixed-ratio component, although the signal improved response efficiency in both groups. In Experiment 3, a poor correlation between responding and reinforcement was produced by a VI schedule onto which the delivery of response-independent food was superimposed. A signal for reinforcement initially elevated responding on this schedule, relative to an unsignaled condition; however, this pattern was reversed with further training. In sum, the present experiments provide little support for the view that signaling reinforcement enhances responding when the response-reinforcer correlation is weak and attenuates responding when this correlation is strong. 相似文献
11.
Activity Structures and the Unfolding of Problem-Solving Actions in High-School Chemistry Classrooms
In this paper, we argue for a more systematic approach for studying the relationship between classroom practices and scientific practices—an approach that will likely better support the systemic reforms being promoted in the Next Generation Science Standards in the USA and similar efforts in other countries. One component of that approach is looking at how the nature of the activity structure may influence the relative alignment between classroom and scientific practices. To that end, we build on previously published research related to the practices utilized by five high-school chemistry teachers as they enacted problem-solving activities in which students were likely to generate proposals that were not aligned with normative scientific understandings. In that prior work, our analysis had emphasized micro-level features of the talk interactions and how they related to the way students’ ideas were explored; in the current paper, the analysis zooms out to consider the macro-level nature of the enactments associated with the activity structure of each lesson examined. Our data show that there were two general patterns to the activity structure across the 14 lessons scrutinized, and that each pattern had associated with it a constellation of features that impinged on the way the problem space was navigated. A key finding is that both activity structures (the expansive and the open) had features that aligned with scientific practices espoused in the Next Generation Science Standards—and both had features that were not aligned with those practices. We discuss the nature of these two structures, evidence of the relationship of each structure to key features of how the lessons unfolded, and the implications of these findings for both future research and the training of teachers. 相似文献
12.
This study aimed at clarifying the relative developmental influences of age, number‐sense and context on primary school children's ability to estimate measures. Children (6‐11 years) were first assessed on three aspects of number‐sense (mental computation, understanding of relative number magnitude and understanding of relations between numbers) and were then assessed on their estimation of length and area within each of two task contexts (a ‘story’ frame and a ‘textbook’ frame). While number‐sense was found to improve with age, estimation did not. However, an ability to use and perceive number relations, together with an understanding of the relative magnitudes of larger numbers, were found to influence children's ability to estimate area. Children of all ages were also found to estimate more accurately in the ‘textbook’ context than in the ‘story’ context. These findings are discussed with reference to the notion of estimation as a situated activity 相似文献
13.
Kathryn Knight 《Interactive Learning Environments》2016,24(4):814-828
This study tested an iPad application using a dichotomous key as a scaffolding tool to help students make more detailed observations as they identified various species of birds on display in a museum of natural science. The Mobile Dichotomous Key (MDK) iPad application was used by groups of fifth- and seventh-grade students. Analysis of the findings suggests that the MDK was equally as effective and in some ways more effective than the educator-led intervention at improving students' scientific observation skills. In general, the scaffolding key in both mobile and educator-led form was found to be more effective for fifth-grade students than for seventh-grade students. In addition, it was found to be effective at improving the level of detail students provided and the number of scientific terms they used, but not at improving the number of valid inferences students made. 相似文献
14.
Jan Helge Kallestad Dan Olweus Francoise Alsaker 《School Effectiveness & School Improvement》2013,24(1):70-94
Using a set of data derived from 42 schools at two points in time and a widely accepted definition of organizational climate, a number of methodological and substantive issues relating to school climate were explored. Via principal component analysis, four dimensions of school climate were identified. In approaching the key issue, under what conditions it is meaningful to speak of a climate dimension as a characteristic of the school (and not some lower‐level unit), it is tentatively proposed that a climate dimension has a ‘unit reliability’ of .15 or more and an ‘aggregate reliability’ of at least .35 in order to be considered a school characteristic. Furthermore, the “longitudinal relative consistency” or stability of the dimensions was examined. It was found that at least three of the dimensions were relatively enduring over time, as they should be according to the definition of school climate. Multilevel analyses suggested that the teacher reports of school climate were fairly robust and generalizable. The thinking and findings in this article are related to recent work in the school improvement and effectiveness field. 相似文献
15.
ABSTRACTExtracurricular student–staff partnership activities are increasingly common in higher education institutions, but concerns have been expressed about their relative inclusivity. In order to contribute to understanding of why students do and do not take part in such initiatives, this study draws on data from a survey of students at four institutions, in three different countries, with established extracurricular partnership programs. Though the findings indicate some preliminary differences between participants at the four institutions, they also demonstrate a number of shared perceptions, including similar understandings of key features of partnership and shared perceptions of barriers to participation. Implications for partnership practice and research are discussed. 相似文献
16.
INTRODUCTION The concept of group signature, first introduced by Chaum and van Heyst (1992), allows each group member to sign messages on behalf of the group, and the receiver can use a group public key to verify the group signature, but cannot reveal the signer. In case of disputes, the group authority can open the group signature and identify the signer, but the outsider cannot identify all previous group signatures gener-ated by the same group member. A group member cannot impersonate… 相似文献
17.
Jay Moore 《Learning & behavior》1976,4(4):441-450
Pigeons responded on a two-key concurrent chains choice procedure with the same level of percentage reinforcement on each key. During the initial links, a choice response on either key occasionally produced a conditioned reinforcer—which on one key was associated with a 15-sec, and on the other key with a 30-sec, interreinforcement interval—or an extinction stimulus. In Part 1, the initial links were equal. With successive decreases in the probability of a reinforcer, choice shifted from preference for the 15-sec terminal link toward indifference. In Part 2, the initial links were unequal and were arranged so that the shorter initial link preceded the 30-sec terminal link. At a high probability of a reinforcer, the pigeons again preferred the 15-sec terminal link. However, at a low probability, the pigeons reversed and preferred the alternate key. It was concluded that the conditioned reinforcers tended to become functionally equivalent at a low probability of a reinforcer, despite the nominally different interreinforcement intervals, with the result that choice was then modulated by the relative size of the initial links. The data are inconsistent with the view that choice and the strength of conditioned reinforcers are isomorphic with the reduction in delay to reward correlated with terminal link stimuli. 相似文献
18.
陆少刚 《淮南职业技术学院学报》2002,2(1):10-13,16
社会经济现象之间存在的错综复杂的联系，多数可以用指数体系来描述，在社会经济现象总体变动中，各个构成因素的变动可以从绝对数和相对数两方面进行研究，一般地，首先计算各个指数，其次建立指数体系，最后进行因素分析，达到反映现象总体变动，各个构成因素变动及对总体变动影响程度的目的。 相似文献
19.
In three between-groups blocking experiments with rats, two concurrent and one forward, several common control procedures
were employed: Reinforced trials with the putative blocking stimulus were either omitted entirely (Kamin control), replaced
by unsignaled reinforcements (Wagner control), or replaced by reinforced trials with a different stimulus (C1 control). In
each experiment, parallel treatments with the target stimulus absent during training served to examine the possibility that
differential responding in tests with the target stimulus might be traced solely to differential exposure to the nontarget
stimuli. In Experiment 1, responding by a concurrent blocking group during the test was no different than responding by a
Kamin control group, and responding by a Wagner control group was greater than that of either of the other groups—a pattern
of results, mirrored in the performance of the target-absent groups, that could be attributed to the elevation of contextual
excitation by unsignaled reinforcement. In Experiment 2, responding in the test by a concurrent blocking group was no different
than that by a C1 control group. In Experiment 3, a finding of less responding by a forward blocking group than by a C1 control
group when the target stimulus was present during training, but not when it was absent, provided plausible evidence of blocking. 相似文献
20.
杨新新 《河南师范大学学报(哲学社会科学版)》2001,28(6):1-5
绝对与相对是马克思主义哲学的一对基本范畴。由于多年来我们一直未能给以足够重视，凡涉及绝对与相对的关系问题，在理论上大多成为难点，而在实践中也因此而造成失误。实际上，从绝对与相对的关系在马克思主义哲学体系中的重要地位和作用来看，从对实践的指导意义来看，绝对与相对的关系贯穿于马克思主义哲学的始终，是理解该哲学理论体系的关键，是应用和发挥该哲学理论以指导实践的重要方法论原则。 相似文献