Directed forgetting in pigeons

Pigeons performed a version of delayed matching-to-sample in which different postsample cues signaled different trial outcomes. Cues to remember (R cues) signaled the usual comparison stimuli. Cues to forget (F cues) signaled either cancellation of comparison stimuli (comparison-omission) or presentation of a sample-independent discrimination (comparison-substitution). As assessed by occasional probe trials, F cues decreased matching accuracy during comparison-omission more than during comparison-substitution. The loss in accuracy of matching in F-cue probes was directly related to length of delays during comparison-omission but not during comparison-substitution. Because trials generally terminated in reward during comparison-substitution but not during comparison-omission, these findings were interpreted as suggesting the importance of end-of-trial reinforcement for the maintenance of short-term memory.     

Directed forgetting among third and seventh graders

The present studies examined the effectiveness of explicit and implicit Forget cues for enhancing memory of to-be-remembered items within a directed forgetting paradigm. Such a paradigm may be viewed as a laboratory analogue to a classroom testing situation where students read through an examination before beginning in order to cue themselves as to which information is important to remember. Subjects were third- and seventh-grade children. Evidence was provided that directed forgetting processes were operative at the time of recall so that memory enhancement did not merely reflect differential rehearsal of the to-be-remembered items during study. When easy partitioning of items into Remember and Forget sets was possible, subjects as young as third graders could benefit from postpresentation Forget cues. The data suggest that postpresentation Forget cues permit a selective search during recall and a consequent reduction in interference from to-be-forgotten items. Applications of these findings to a classroom testing situation were discussed.     

Directed forgetting in pigeons: Analysis of cue functions

In delayed matching-to-sample with pigeons, brief postsample cues signaled different trial outcomes. The normal comparison stimuli followed the cue to remember (R cue). In the comparison-omission procedure, comparison stimuli and reinforcement were omitted following the cue to forget (F cue). In the comparison-substitution procedure, comparison stimuli were replaced by a single stimulus and reinforcement for a single response following the F cue. Infrequent probe trials revealed that F cues disrupted matching, with the amount of accuracy loss dependent on the length of the cue-comparison delay. These results, however, were found only with the comparison-omission procedure (Experiment 1). Replacing the comparison stimuli with another simultaneous (unconditional) discrimination revealed no accuracy loss in F-cue probes (Experiment 2), even though choice latencies were again lengthened by F cues. These results suggest that, while the F cue interferes with performance at the time of a retention test by slowing choices, it also interferes with sample retention. Alternative models of the cuing effect and its apparent dependence on end-of-trial reward are outlined.     

Directed forgetting effects in pigeons: Remember cues initiate rehearsal

Pigeons were trained in a two-choice delayed matching-to-sample task with red and green hues. A brief postsample cue (a vertical or horizontal line) signaled whether the comparison stimuli would be presented or omitted on each trial. Comparison stimuli were always presented following the remember-cue (R-cue) trial, but never following the forget-cue (F-cue) and no-cue trials. In Experiment 1, matching accuracy on F-cue and no-cue trials was equivalent and was considerably inferior to accuracy on R-cue trials. In Experiment 2, the placement of the postsample cue was manipulated. Matching accuracy decreased as the R cue was delayed in the retention interval, but performance in the F-cue condition was not affected. These data indicate that the no-cue condition can function as an implicit F cue and that the R cue can function to initiate and maintain rehearsal.     

Role of proactive interference in infantile forgetting

Ontogenetic changes in the role of proactive interference in augmenting forgetting were tested with 444 rats as subjects. In Experiment 1, Phase 1 (the source of proactive interference) included events that were contingent or not contingent on responding in the context of either the Phase 2 training apparatus or a distinctly different apparatus. After learning a spatial discrimination for Phase 2, retention tests were given after intervals of 2 min, 1 day, 7 days, 30 days, or 65 days. The results indicated: (1) infantile amnesia, and (2) proactive interference for infant rats but not for adults, in spite of substantial simple forgetting among adults. Experiment 2 extended the test to a go/no-go avoidance task. The results of Experiment 2 gave some indication that infants were more susceptible than were adults to proactive interference over short intervals, but the generality of this relationship was sufficiently ambiguous as to suggest different mechanisms of interference for the discrimination and go/no-go tasks. These data indicate multiple mechanisms of infantile forgetting that may vary with certain characteristics of the task.     

Ontogenetic forgetting of stimulus attributes

The effects of age on the forgetting of stimulus attributes in a differential fear-conditioning paradigm were examined with 18- and 70-day-old rats tested in either the original conditions or shifted stimulating conditions at one of three retention intervals (1, 48, and 120 h). Adults displayed significant shifts at each retention interval, with those tested in the original context displaying greater fear than those tested in the shifted conditions. By contrast, by 48 h the 18-day-olds had forgotten the specific attributes of the training situation and began treating the two stimulating conditions as functionally equivalent (Experiment 1). In Experiment 2, we tracked the ontogenetic emergence of adult-like memory for stimulus attributes and found a dramatic increase in memory capability by 25 days of age. Experiment 3 illustrated that the forgotten memory attributes of infants may be retrieved by administering a 90-sec cuing treatment 10 min prior to the 48-h test. Implications for the phenomenon of infantile amnesia are discussed.     

BCH-代数的有向集

提出了BCH-代数上的有向集和有向闭包集的概念,并对有向集和有向闭包集进行了初步的讨论.     

Stimulus salience and asymmetric forgetting in the pigeon

Pigeons were trained using a symbolic delayed matching-to-sample procedure involving bright versus dim houselight samples. We hypothesized that when sample stimuli differ in salience, increasing the size of the retention interval will affect performance on trials initiated by the more salient sample only. In agreement with this prediction, accuracy following the dim sample did not decline as the retention interval increased, whereas accuracy following the bright sample declined to well below 50% correct. In a second experiment, the less salient (dim) sample from Experiment 1 was arranged as the more salient sample in a sample/no-sample procedure. Accuracy on dim sample trials then declined to well below 50% correct as the retention interval increased, whereas accuracy on no-sample trials remained constant. The results suggest that when sample stimuli differ in salience, pigeons may transform the nominal discrimination task into a detection task in which they respond on the basis of the presence or absence of the more salient sample.     

The development of forgetting and reminiscence

Many theoretical positions on memory development anticipate that forgetting rates should vary substantially with age. The nature of these age variations is also relevant to many applied questions about child development that have major social policy implications, such as the veracity of children's eyewitness testimony and the long-term effectiveness of classroom instruction. Surprisingly, developmental studies of long-term retention have repeatedly produced the puzzling finding that forgetting rates are age invariant. It now seems, however, that these null age trends may have been artifacts of variables such as measurement insensitivity, floor effects, and stages-of-learning confounds. Assuming, as some later studies suggest, that forgetting rates vary with age when these factors are controlled, there are three overriding questions that must be dealt with in the developmental analysis of forgetting: the relative importance of storage failure versus retrieval failure, the relative importance of true forgetting processes versus test-induced processes, and the relative importance of storage-based reminiscence versus retrieval-based reminiscence. We describe a framework (disintegration/redintegation theory) that provides a conceptual environment within which research on these questions can progress. This framework, which evolved from fuzzy-trace theory, reinterprets processes such as storage failure, retrieval failure, restorage, and retrieval relearning in terms of levels of featural integration in traces (i.e., the extent to which contextual information is integrated with core semantic gist to produce a coherent representation). The theory is implemented in a mathematical model (the trace-integrity model) whose parameters deliver measurements of relevant memory processes on a common ratio scale. In a series of experiments, the model was used to study the theory's predictions about the contributions of these memory processes to long-term retention in subjects between the ages of 7 and 70. All the experiments were standard long-term retention designs (an initial acquisition session, followed by a 1-2-week forgetting interval, followed by a series of retention tests).(ABSTRACT TRUNCATED AT 400 WORDS)     

Fuzzy有向图中有向路及有向圈存在的条件

对Fuzzy有向图定义了邻接矩阵,并通过对邻接矩阵幂的讨论,探讨了Fuzzy有向图中从有向途径中分离有向路的条件,有向圈及有向Hamilton圈存在的条件。     

Differential outcome expectancies and directed forgetting effects in pigeons

Pigeons were trained in a two-choice delayed matching-to-sample task with red and green hues. A brief postsample cue (a vertical or horizontal line) signaled whether the comparison stimuli would be presented or omitted on each trial. Comparison stimuli were always presented following the remember (R) cue, but never following the forget (F) cue or no-cue trials. One group of birds, the differential outcome (DO) group, received reinforcement with a probability of 1.0 for correct responses following one sample stimulus and a probability of 0.2 for correct responses following the other sample stimulus. The nondifferential outcome (NDO) group received reinforcement with a probability of 0.6 for correct responses to either stimulus. The effect of postsample cues was greater for the DO group than for the NDO group. Relative to the NDO group, the DO group displayed higher accuracy on R-cue trials and lower accuracy on F- and no-cue trials. Both tendencies contributed to the enhanced cue effectiveness obtained in the DO group. The results indicate that outcome expectancies are subject to maintenance rehearsal, which comes under the control of postsample R and F cues. They also suggest that maintenance rehearsal may be easier to sustain under DO conditions than under NDO conditions when a memory test is anticipated, but that it may be easier to terminate maintenance rehearsal under DO conditions when a memory test is not anticipated. The results are inconsistent with the assumption that the rehearsal of outcome expectancies is automatic.     

Time dependent effects of double cuing in directed forgetting

Previous research in directed forgetting in pigeons has focused on the effect of single forget cues (F-cues) interpolated within the retention interval in delayed matching-to-sample (DMTS). The present series of experiments focuses on the ability of a remember cue (R-cue) to cancel the effects of a previously presented forget cue both when the forget cue occurs within the retention interval and when the forget cue precedes sample presentation. In the first experiment, an R-cue decreased the effect of an F-cue within the same retention interval in successive DMTS if the R-cue immediately followed the F-cue, but not if the second cue was delayed until the end of the retention interval. In Experiment 2, the double-cue effect was extended to choice DMTS. In addition, when a novel stimulus replaced the R-cue in the double-cue probe trials, matching performance was not restored, indicating that through its conditioning history the R-cue had gained control over memory processes in a direction opposite to that of the F-cue. Experiment 3 presents evidence that presample R- and F-cues can also effectively gain control over matching performance. Matching to R-cued samples was superior to matching to F-cued samples. When F-cued samples were followed immediately by R-cues, matching performance was not restored to R-cue levels, suggesting differential encoding of the R-cued and F-cued samples.     

Does contextual change determine long-term forgetting?

A series of experiments were run to test the hypothesis that “spontaneous forgetting” could result from subtle contextual changes. The first experiment demonstrated that when Sprague-Dawley male rats are trained in a runway alley with a food reinforcer, retention performance is dramatically affected by a change in the pattern of the walls of the training apparatus when testing takes place 1, 3, or 5 days following training and not after 1 week. Experiment 2 demonstrated that this performance deficit cannot be alleviated by any of the three selected cuing treatments, whereas “spontaneous forgetting” (resulting from a training-to-test interval of 14 days) can be. These data indicate that the detrimental effect of contextual change reduces over time, and that such an effect cannot be interpreted in terms of retrieval failure. These results lend strong support to the argument that the disruptive contextual change effect is basically different from the disruptive effect that results from an extended training-to-test interval.     

Retroactive interference and rate of forgetting in delayed matching-to-sample performance

Previous evidence suggests that a disruptive stimulus presented during the delay interval of a delayed matching-to-sample trial increases the rate of forgetting by pigeons. However, disruptive events have generally been presented for a period of time proportional to the delay interval. Thus, the observed increase in forgetting may be the result of greater exposure to these events at longer delays than at shorter ones. This possibility was examined by comparing the effects of houselight illumination for the entire delay, half the delay, or a constant 1.5 sec of each delay on pigeons’ delayed matching-to-sample accuracy. Presenting the houselight for a period of time proportional to each delay (i.e., the entire delay or half the delay) impaired accuracy more at longer delays than at shorter delays. By contrast, when the houselight was illuminated for 1.5 sec, irrespective of delay length, there was a greater impairment in accuracy at shorter delays than at longer delays. Thus, the increased rate of forgetting previously reported in the literature may be the result of unequal application of a disrupting stimulus across delays.     

基于路径的有向图顶点的重要度计算方法

有向图中顶点的重要度分析及其计算方法被广泛应用于控制论、信息技术等领域.提出一种基于路径的有向图顶点的重要度计算方法,使用定量分析的方法计算每个顶点在整个有向图中的重要程度,并采用一种基于迭代计算方法,提高计算速度.     

有向图中路径矩阵的实现及其算法研究

在已知有向图的邻接矩阵的基础上 ,分析邻接矩阵的特点 ,从而给出了一种直接由邻接矩阵求解路径矩阵的新算法 ,并对其算法进行了分析和研究 .     

基于路径的有向图顶点的重要度计算方法

有向图中顶点的重要度分析及其计算方法被广泛应用于控制论、信息技术等领域.提出一种基于路径的有向图顶点的重要度计算方法,使用定量分析的方法计算每个顶点在整个有向图中的重要程度,并采用一种基于迭代计算方法,提高计算速度.