Overshadowing of situational cues with variable but not fixed intertrial intervals

In two experiments, we examined the conditions under which signaling an unconditioned stimulus (US) with a nominal conditioned stimulus (CS) interferes with the conditioning of situational cues in defensive freezing in the rat. Subjects received footshock USs that were (1) either signaled or unsignaled and (2) either varied or fixed in their temporal location within the conditioning session. Experiment 1, with only one trial per session, yielded no evidence that signaling affected pretrial freezing using either a fixed or variable interval between placement in the context and shock onset. In a test in which no CSs or footshocks were presented, groups that previously had received footshock at a fixed temporal location showed greatest freezing at around that same time. For groups that had received footshocks at various times, freezing declined across the test session. Experiment 2 showed overshadowing of pretrial freezing after more extensive conditioning with many trials per session, but only if the intershock intervals were variable rather than fixed.     

Influence of intertrial interval duration on the intertrial agreement effect in delayed matching-to-sample with pigeons

Accuracy on even-numbered trials was assessed as a function of (1) the relation between the sample on the immediately preceding trial and that on the current trial and (2) the length of the intertrial interval (ITI) that intervened between odd- and even-numbered trials. A relatively long interval intervened between pairs of trials in the clustered-dyads procedure, whereas this interval was equal to the ITI in the massed-trials procedure. Both procedures revealed an intertrial agreement effect in that accuracy was higher when the sample on the immediately preceding trial was identical rather than opposite. A decrease in the magnitude of this effect at longer ITIs was apparent only in the clustered-dyads procedure. The insensitivity of the intertrial agreement effect to variations in ITI in the massed-trials procedure may reflect floor effects and the carryover of memory from multiple prior trials that mask the true magnitude of the intertrial agreement effect at short ITIs.     

The effects of intertrial and feature-target intervals on operant serial feature-positive discrimination learning

The effects of intertrial interval (ITI) and feature-target interval (FTI) on the nature of learning in discrete-trial operant serial feature-positive (feature → target+ / target?) discrimination training were examined in two experiments with rats. Discrimination performance was acquired more rapidly with longer ITIs and shorter FTIs. In contrast, transfer to a separately trained target was greater with shorter ITIs regardless of FTI. Persistence of discrimination performance after feature extinction was greater with longer ITIs. Only the last of these performance measures showed evidence for invariance with constant ITI/FTI ratios. The results are discussed in the context of theories of occasion setting.     

Differential inflation with short and long CS-US intervals: Evidence of a nonassociative process in long-delay taste avoidance

Three experiments were performed to investigate the learning process underlying the phenomenon of long-delay taste conditioning. An associative model views taste avoidance as due to a conditioned stimulus-unconditioned stimulus (CS-US) associative structure, despite the long interval interposed between the flavor and illness. A nonassociative account of this avoidance behavior posits that avoidance stems from the interaction of two nonassociative processes: habituation of neophobic avoidance to a novel taste, and the poison-induced dishabituation of this process. A postconditioning inflation manipulation was used to discriminate between these two views. It has been demonstrated that enhanced responding with a US inflation manipulation depends, in part, on a previously conditioned association. Therefore, if long-delay taste avoidance arises from nonassociative processes, an inflation manipulation should not affect conditional responding. Experiment 1 demonstrated a delay of reinforcement effect, enhanced avoidance of saccharin in the immediate/inflation group, and no effect of inflation in the delay group and sham controls. Experiment 2 revealed that this differential effect of inflation is not due to absolute differences in the strength of the avoidance response. In Experiment 3, we investigated a potential associative learning mechanism that could account for the differential inflation effect. Together, the present results support the various predictions of a nonassociative account of long-delay taste avoidance.     

Outcome-selective effects of intertrial reinforcement in a Pavlovian appetitive conditioning paradigm with rats

The outcome-selective effects of presenting intertrial unconditioned stimuli (USs) in a rat appetitive conditioning paradigm were examined in two experiments. In both experiments, two stimuli were paired with different outcomes, while one of these outcomes was also presented in the intertrial interval (A+, B*, +). Two measures of learning, stimulus-elicited magazine approach and Pavlovian-to-instrumental transfer, were used to examine these effects. The presence of freely occurring outcomes in the intertrial interval (ITI) was observed to interfere more with the learning of a new association (Experiment 1) and to degrade more an already established association (Experiment 2) when the conditioned stimulus had been paired with the same outcome as that occurring in the ITI. An outcome-selective effect of ITI USs distinguishes among accounts of contingency based on general performance, attentional, and motivational mechanisms from those based on more specific associative mechanisms. Overall, the data highlight the importance of specific encoding processes in the analysis of associative learning.     

Effect sizes,confidence intervals,and confidence intervals for effect sizes

The present article provides a primer on (a) effect sizes, (b) confidence intervals, and (c) confidence intervals for effect sizes. Additionally, various admonitions for reformed statistical practice are presented. For example, a very important implication of the realization that there are dozens of effect size statistics is that authors must explicitly tell readers what effect sizes they are reporting. With respect to confidence intervals, when interpreting a 95% interval, we should never say that we are 95% confident that our interval captures the estimated population parameter. It is explained that effect sizes should be reported even for statistically nonsignificant effects. And, most importantly of all, it is emphasized that effect sizes should not be interpreted using Cohen's benchmarks. Instead, we ought to interpret our effects in direct and explicit comparison against the effects in the related prior literature. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 423–432, 2007.     

Effects of intertrial reward and/or nonreward placements during a 20-second intertrial interval on single-alternation training in rats

Seventy male hooded rats received single-alternation runway training in which goalbox placements were interpolated during the 20-sec intertrial interval. Placements provided alternating reward/ nonreward, random reward/nonreward, continuous reward, or continuous nonreward. Relative to nonplaced controls, alternation performance was reliably facilitated only by intertrial alternation placements which re-presented the goal event of each immediately preceding instrumental trial. All other intertrial procedures reliably impaired alternation performance. Degree of impairment was graded from least to most as follows: intertrial alternation placements with the goal event opposite to that of each immediately preceding instrumental trial, intertrial placements with continuous non-reward, intertrial placements with continuous reward, and intertrial placements with random reward/nonreward.     

The CS-US interval (ISI) function in rabbit nictitating membrane response conditioning with very long intertriai intervals

In Experiment 1, four values of conditioned stimulus-unconditioned stimulus interval, or interstimulus interval (ISI) (200, 500, 800, and 1,100 msec) were studied in one trial/day acquisition of the conditioned nictitating membrane response of the rabbit. The 1,100-msec ISI group was superior to the other groups, contrary to the usual findings of ISI studies in the conditioning literature. In Experiment 2, effective conditioning levels were attained with an ISI as long as 2,200 msec, when the intertriai interval was set at either 24 or 48 h. Results are interpreted in terms of the role of orienting responses in the conditioning process.     

Effect of intertrial interval on variable-interval discrete-trial barpressing

In seven experiments, an effect of the intertriai interval (ITI) duration on barpressing by rats was studied. A stimulus signaled a 15-sec variable-interval trial. The first response after the interval elapsed turned the stimulus off and was rewarded with food. Trials were separated by long (about 300 sec) or short (about 10 sec) ITIs. A within-subjects design established that response rate on trials after long ITIs was lower than that after short ITIs (Experiments 1 and 3–7). The effect was not cumulative (the effect of one and five consecutive short ITIs was the same). Response rate after short and long ITIs was the same when a between-subjects design was used (Experiment 2). Response rate was higher after 160-sec ITIs than after 300-sec ITIs, suggesting that the ITI duration at which all longer ITIs are treated the same (i.e., the upper limit) is greater than 160 sec (Experiment 3). When food, the trial stimulus, a novel stimulus, or a familiar stimulus never paired with food, was presented 10 sec before the next trial during some of the long ITIs, response rate on the next trial was similar to that found after 10-sec ITIs (Experiments 4–6). This similarity suggested that these events could mark the start of the ITI. However, the familiar stimulus did so only when it reliably predicted that the next trial would occur after a short interval. The effect of ITI duration on responding was apparently attributable to response latency. Response latency was greater after long ITIs, but once responding began, it was similar after long and short ITIs (Experiment 7).     

中国全面建设小康社会所面临的国际战略环境分析

19-20世纪是彻底改变中国和美国命运的二百年.立国不久的美国在沉寂了半个多世纪之后迅速崛起,最终在19世纪末挤进世界强国的行列,给20世纪的国际关系带来了全新的局面.中国则历经了从衰落到屈辱的一个半世纪,在多年艰苦探索之后才于20世纪的最后20年进入持续快速的发展时期.与美国相比,中国真正的大发展时代整整晚了一个世纪有余.本文从中美两个大国不同时期崛起时的不同国际环境,分析了当代中国现代化进程的艰巨性与复杂性.展望21世纪全面建设小康社会的战略任务,我国面临着复杂的国际环境等诸多挑战,但前景依然是光明的.     

Serial discrimination reversal learning in pigeons as a function of intertrial interval and delay of reinforcement

Pigeons learned a series of reversals of a simultaneous red-green visual discrimination. Delay of reinforcement (0 vs. 2 sec) and intertrial interval (ITI; 4 vs. 40 sec) were varied across blocks of reversals. Learning was faster with 0-sec than with 2-sec delays for both ITI values and faster with 4-sec ITIs than with 40-sec ITIs for both delays. Improvement in learning across successive reversals was evident throughout the experiment, furthermore, even after more than 120 reversals. The potent effects of small differences in reinforcement delay provide evidence for associative accounts and appear to be incompatible with accounts of choice that attempt to encompass the effects of temporal parameters in terms of animals’ timing of temporal intervals.     

Retrieval practice after multiple context changes,but not long retention intervals,reduces the impact of a final context change on instrumental behavior

Recent evidence from this laboratory suggests that a context switch after operant learning consistently results in a decrement in responding. One way to reduce this decrement is to train the response in multiple contexts. One interpretation of this result, rooted in stimulus sampling theory, is that conditioning of a greater number of common stimulus elements arising from more contexts causes better generalization to new contexts. An alternative explanation is that each change of context causes more effortful retrieval, and practice involving effortful retrieval results in learning that is better able to transfer to new situations. The current experiments were designed to differentiate between these two explanations for the first time in an animal learning and memory task. Experiment 1 demonstrated that the detrimental impact of a context change on an instrumental nose-poking response can be reduced by training the response in multiple contexts. Experiment 2 then found that a training procedure which inserted extended retention intervals between successive training sessions did not reduce the detrimental impact of a final context change. This occurred even though the inserted retention intervals had a detrimental impact on responding (and, thus, presumably retrieval) similar to the effect that context switches had in Experiment 1. Together, the results suggest that effortful retrieval practice may not be sufficient to reduce the negative impact of a context change on instrumental behavior. A common elements explanation which supposes that physical and temporal contextual cues do not overlap may account for the findings more readily.     

混合算法逼近相对渐近非扩张映像不动点

在一致凸且一致光滑的Banach空间的框架下,对于相对渐近非扩张映像在对算子或集合缺乏紧性条件限制的情况下,采用混合方法得到了三步迭代程序的强收敛性,所得结果改进和推广了Matsushita,Takaashi,Qin,Su等一些人的最新研究结果。     

终身教育与终身学习的概念解读与关系辨析

终身教育思想和终身学习理念是两种世界性的教育思潮,两者在侧重点、针对的教育阶段、实施的主体等方面存在不同,但它们的教育目的、本质存在着一致性,并且两者的关系紧密,互为前提、互相支撑。     

The effect of filled and empty intervals on clock and memory processes in pigeons

According to the mixed memory model (Penney, Gibbon, & Meck, Journal of Experimental Psychology: Human Perception and Performance, 26, 1770–1787, 2000), different clock rates for stimuli with different nontemporal properties must be stored within a single reference memory distribution in order to detect a difference between the clock rates of the different signals. In Experiment 1, pigeons were trained in a between-subjects design to discriminate empty intervals (bound by two 1-s visual markers) and filled intervals (a continuous visual signal). The intervals were signaled by different visual stimuli, and they required responses to different sets of comparison stimuli. Empty intervals were judged as being longer than filled intervals. The difference between the point of subjective equality (PSE) for the empty intervals and the PSE for the filled intervals increased proportionally as the magnitudes of the anchor duration pairs were increased from 2 and 8 s to 4 and 16 s. In Experiment 2, the pigeons were trained to discriminate intervals signaled by the absence of houselight illumination (Group Empty) or the presence of houselight illumination (Group Filled). The psychophysical timing functions for these intervals were identical to each other. The results of Experiment 1 indicate that memory mixing is not necessary for detecting a timing difference between empty and filled intervals in pigeons. The results of Experiment 2 suggest that the nature of the stimuli that signal the empty and filled intervals impacts how pigeons judge the durations of empty and filled intervals.     

Effects of stimulus dimension and of trial and intertrial illumination on acquisition of a match/mismatch task by pigeons

Birds were trained on a higher order conditional discrimination task, one that required birds to match samples and comparisons on some trials and to mismatch on other trials. Which task component was in effect was indicated by the level of chamber illumination (houselight-on and houselight-off instructions). Acquisition of the components of a color (red and green) match/mismatch task in the first half of the experiment was not differentially affected by the level of illumination associated with each task component, by houselight changes per se, or by the level of illumination during the intertriai interval (ITI). However, when shapes (plus and circle) were used to train the task in the second half of the experiment, performance on the houselight-cued task component exceeded performance on the dark-cued task component, and ITI illumination facilitated performance on both task components. These results suggest that attention to shape stimuli, but not to colors, may vary systematically as a function of chamber illumination level.     

Lifelong learning: a policy concept with a long past but a short history

This article examines the continuities and discontinuities in the international problematisation of education across the lifespan as an education policy, currently conceptualised as lifelong learning. Through the critical examination of international organisations’ policy documents, this paper demonstrates that while on the one hand there is a pattern in the way the problematisaton has been carried out (the continuities), on the other hand the translation of the problematisaton into policy has been punctuated by major discontinuities. Lifelong learning as a policy concept has introduced strong discontinuities that have ensured its acceptance worldwide: a policy with a small degree of political operationalisation that simultaneous discursively combines different political orientations.     

浅析现代跳远技术教学特征

通过查阅跳远技术教学的研究成果,结合跳远技术教学的特点和教育学、心理学理论对跳远技术教学中技术练习途径、教学实施控制、学生学习方式3个方面进行分析,探讨现代跳远教学规律,为跳远教学提供参考.