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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).

A comprehensive battery of commonly used neuropsychological tests, including the WMS Associate Learning and Visual Reproduction subtests, forming the focus of this study, were administered to a southern African sample (n = 33, age range 18-40). This sample composed of black South African, IsiXhosa speakers with an educational level of Grade 11 and 12, derived through DET and former DET schooling. The gender demographics were as follows; females n = 21 and males n = 12. This sample was purposefully selected based on current cross-cultural research which suggests that individuals matching these above-mentioned demographics are significantly disadvantaged when compared to available neuropsychological norms. This is due to the fact that current norms have been created in contexts with socio-cultural influences; including culture, language and quantity and quality of education distinctly dissimilar to individuals like that composed in the sample. Hence the purpose of this study was fourfold namely; 1) Describe and consider socio-cultural factors and the influence on test performance 2) Provide descriptive and preliminary normative data on this neuropsychologically underrepresented population 3) Compare test performance between age and gender through stratification of the sample and finally to 4) Evaluate the current norms of the two WMS subtests and assess their validity for black South Africans with DET and former DET schooling with comparisons to the results found in the study. Information derived from the statistical analyses indicated that a higher performance in favour of the younger group over the older age range was consistently found for both WMS subtests. With regards to gender, some higher means were evident for the male population in the sample than was produced by the female group. Lastly, due to the fact that most scores derived from the sample were considerably lower when compared to the available norms, it is felt that socio-cultural factors prevalent to this population are a significant cause of lower test performance and thus warrant the development of appropriate normative indicators.

by Siu-yee Wong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1989. / Bibliography: leaves 39-41.

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

No description available.

The latent variable structure of the Wide Range Assessment of Memory and Learning (WRAML) test (Sheslow & Adams, 1990) has been suggested to contain an attention factor comprised of the subtests: Finger Windows, Number/Letter, and Sentence Memory. The multidimensional nature of the attention construct has not been addressed in previous studies with the WRAML. The present investigation was designed to investigate the relationship between the WRAML subtests and a diverse battery of attention tests. Three competing latent variable models of the attention construct were developed in which the WRAML subtests were hypothesized to be affected by different components of attention. The battery, administered to 120 males between 9 and 14 years of age consisted of the WRAML subtests, Digit Span, Arithmetic, Coding, Trails A, Trails B, Category Test, Speech Sounds Perception Test, Wisconsin Card Sorting Test, and a Continuous Performance Test.Significant correlations were obtained between all the tests in the battery. Confirmatory factor analysis results suggested that a four factor model of attention (Focus-Execute, Shift, Sustain, Encode) similar to that obtained by Mirsky and others, (1991) was the best data fit. The WRAML subtests were affected by the Encode element of attention in the current analysis. / Department of Educational Psychology

Today, the use of embedded Dynamic Random Access Memory (eDRAM) is increasing in our electronics that require large memories, such as gaming consoles and computer network routers. Unlike external DRAMs, eDRAMs are embedded inside ASICs for faster read and write operations. Until recently, eDRAMs required high manufacturing cost. Present process technology developments enabled the manufacturing of eDRAM at competitive costs. Unlike SRAM, eDRAM exhibits retention time bit fails from defects and capacitor leakage current. This retention time fail causes memory bits to lose stored values before refresh. Also, a small portion of the memory bits are known to fail at a random retention time. At test conditions, more stringent than use conditions, if all possible retention time fail bits are detected and replaced, there will be no additional fail bits during use. However, detecting all the retention time fails requires long time and also rejects bits that do not fail at the use condition. This research seeks to maximize the detection of eDRAM fail bits during test by determining effective test conditions and model the failure rate of eDRAM retention time during use conditions.

No description available.

The Aronson Shopping List is a short-term memory test which integrates current knowledge of brain-behavior relationships in assessment. The test was designed to detect deficiency in fluid intelligence. The goal of this study was to standardize the test on an elderly population. The sample was composed of 67 males and females whose ages ranged from 62 to 89 years. It was found that recent stressful events did not account for variation of performance on the ASL. The reliability of the test, established by means of a test and alternate form retest procedure, was found to be .70 after an average of eleven months. Percentiles are presented indicating performance comparisons. Further experimentation would be needed to establish whether the test would be useful to designate organic brain pathology.