No description available.

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Note:

The role of various sources of proactive and retroactive interference in Delayed-Matching-to-Sample (DMTS) performance of five capuchin monkeys (Cebus apella) was examined in a series of four experiments. The DMTS trials were presented in a semi-automated Wisconsin General Test Apparatus (WGTA) with junk objects serving as stimuli. The first experiment assessed the effects of delay interval (10 or 40 seconds), sample reward (present or absent), and nature of delay interval stimulation (dark or illuminated) on DMTS performance when sample and choice stimuli are drawn from a large pool of stimuli. Performance was better when the sample response was rewarded than when it was not. Correct responding was initially more frequent after dark delays than after illuminated delays; however, with continued training the effects of delay interval illumination disappeared. There was no significant difference in performance with a 10 second and a 40 second delay interval. The second experiment consisted of two replications of Experiment I: one with the sample and choice stimuli drawn from a large pool (480) of objects and the other with stimuli drawn from a small pool (2) of objects. When stimuli were drawn from the small pool of objects, performance was markedly poorer than when stimuli were drawn from the large pool. A significant delay interval effect was observed in the small pool task, but as in Experiment I no such effect was observed when stimuli were drawn from a large pool. Performance was poorer on the small pool condition when the delay interval was illuminated than when the houselights were extinguished. However, unlike the effect observed in Experiment I, illuminated delay performance decrements persisted after continued training. No illumination effect was observed for the large pool replication of Experiment II. In both the large and small pool replications, performance was again inferior after nonrewarded sample responses than after rewarded sample responses. Experiment III was designed to test the hypothesis that animals learn to use delay interval stimuli as cues to remember sample stimuli. After extended training on the small stimulus pool condition with delay intervals illuminated, a number of probe trials were presented. On probe trials, the stimuli previously displayed to the subjects during the delay interval (a yellow and white opaque screen) and the stimuli previously displayed during the intertrial interval (a black opaque screen) were reversed. Contrary to the predictions of the retention-cue hypothesis, DMTS performance was no lower on probe trials than on control trials. The final experiment was designed to test the hypothesis that emotionally significant events occurring after the sample presentation period can disrupt DMTS performance by displacing the sample stimulus trace from a limited capacity memory store. In order to insure that the effects of the independent variable not be obscured by floor effect, an intermediate sized (52) pool of objects was used in this experiment. After a pretraining phase, a number of probe trials were presented with a novel sample incentive. As predicted, performance was significantly poorer when the type of incentive was unexpected than when it was expected. These results were interpreted as evidence that animals are more sensitive to the effects of retroactive interference when proactive interference is high (small stimulus pool) than when it is low (large stimulus pool). It was also suggested that emotional reactions can serve as powerful sources of retroactive interference in DMTS performance. These effects occur regardless of whether the emotional response is negative (sample nonreward) or positive (novel sample reward).

published_or_final_version / abstract / Speech and Hearing Sciences / Master / Master of Philosophy

Rumination is known as compulsive and recurrent self-focused thoughts concerning symptoms, causes and consequences of personal distress. Previous research suggested that the habitual use of rumination in daily life, especially among depressed patients, was related to working memory impairment. Here we examined how induced rumination affects the functioning of working memory. In our experiment, participants were randomly assigned to go through either rumination or distraction induction procedures. Then, they were assessed by a computer task in which they were asked to sort three words in either forward or backward order. The three words were either of negative or neutral valence. Accuracy and response latency were recorded to estimate the functioning of their working memory. To examine the pure impact of state rumination on working memory, we recruited participants from healthy population in experiment 1. Recruiting non-depressed people helps isolate rumination from Major Depressive Disorder (MDD) so that the effect of rumination state can be explored in the absence of the mood problems and cognitive deficits related to MDD. The relationship between trait rumination and working memory performance among non‐depressed people was also reviewed. It was found that participants’ accuracy in sorting negative words was lower than neutral words in forward sorting trials after rumination induction. This performance pattern was not observed in distraction group, implicating that rumination caused an increased difficulty for non‐depressed people to encode negative information when they were ruminating. In experiment 2, we aimed at investigating the working memory performance when depressed patients were ruminating. Depressed patients and matched healthy control were recruited to go through the same experimental procedures as in experiment 1. An elevated accuracy for negative words and an improved performance, in terms of higher accuracy and lower response latency, for forward sorting trials after rumination induction were observed. The finding suggested that state rumination caused depressed patients’ working memory to be more prepared to encode information, especially negative one. The results demonstrated that the impact of rumination state on working memory is consistent with the principle of cognitive congruency. Information that is congruent with the self‐related representation tends to have preferential access to the working memory. Implication of our findings on MDD would be discussed in the light of the observed influence of rumination on working memory functioning. / published_or_final_version / Clinical Psychology / Master / Master of Social Sciences

The principle purpose of this study was to investigate the short term auditory storage and retrieval abilities of skilled interpreters for the deaf. Secondary attention was given to age, sex, and educational level variables related to recall abilities. It was assumed that the task of interpreting spoken English to ASL involved short term auditory storage, the efficacy of which was related to chunking abilities of the listener. Measures of short term storage for familiar and novel information (sentences) were employed by estimates of chunking efficiency. Three groups of ten subjects each made up the sample population. Group A was composed of individuals with interest in but limited knowledge of sign language. Group B was composed of individuals with no knowledge of sign language. Group C was composed of individuals holding the Comprehensive Skills Certificate from the National Registry of Interpreters for the Deaf. Free-recall short term storage tasks were utilized to evaluate recall efficiency of the sample groups for familiar and unfamiliar information. English proverbs were used for the familiar stimuli and novel sentences generated from the proverbs were used for the unfamiliar stimuli. Results indicate that skilled interpreters perform extremely efficiently on recall tasks involving conceptually accurate recall of novel sentences. No significant relationship was noted between age, sex, and educational level factors and recall scores. The results were interpreted as supporting the hypothesis that skilled interpreters for the hearing impaired are efficient chunkers of linguistic information. A discussion of the results and needs for further research are presented.

No description available.

The eight experiments reported in this thesis are designed to investigate the idea that in verbal short-term memory (STM) material decays over time and this decay is prevented by rehearsal. It follows that the capacity of STM when measured in words should be inversely proportional to the time taken to rehearse the words. Consequently, subjects should be able to recall more short duration words than long duration words. In contrast to this hypothesis is the idea that the capacity of STM is a fixed number of chunks, where chunks are a structural characteristic of the material. The first four experiments are designed so that these alternative hypotheses produce conflicting predictions and, in all cases, the hypotheses derived from decay theory are supported. It is shown that serial recall performance is very well predicted by the time taken to say the words and that the relationship between word duration and recall is of the type predicted by decay theory. The second set of experiments are based on the assumption that both STM and long-term memory (LTM) contribute to performance in serial recall tasks. The purpose of the experiments is to determine whether it is the STM or LTM component that is sensitive to word duration. It is predicted, in line with a decay theory of forgetting in STM, that the STM component is sensitive to word duration. The experiments are designed to produce sizable contributions from both stores in order to test this hypothesis. The results support the hypothesis in showing that variables known to affect STM, such as acoustic similarity, interact with word duration, while variables known to affect LTM, such as repeated presentations of the same list, show no such interaction. The results are interpreted in terms of decay theory and the different versions of this theory that have been proposed are considered. It is concluded that while no version of the theory is completely adequate, there is no evidence that invalidates the central assumptions, viz. that in STM items are forgotten by decay and that one of the functions of rehearsal is to prevent this decay.

Based on the review of literature, it has been demonstrated that anxiety has some detrimental effects on the short-term memory functions of the college student. In order to improve the experimental methodology, the present study combined Type I and Type II studies of short-term memory as a function of anxiety. The two were combined so that the major criticisms in each study were controlled.