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Semantic organization and verbal memory efficiency in patients with schizophrenia.

The role of semantic organization in verbal memory efficiency in schizophrenia was investigated. Patients and healthy controls were administered a free-recall task involving 1 nonsemantically organizable list, 1 list organizable in semantic categories with typical instances, and 1 list organizable in semantic categories with atypical instances. Reduced semantic organization was observed in patients. Regression analyses showed that the semantic clustering score in the atypical organizable list made a significant contribution to recall performance in patients. When semantic clustering was controlled, the effect of diagnosis on free recall was significant. These results suggest that depth of semantic organization is a crucial factor of verbal memory performance in schizophrenia. However, semantic organizational deficit does not account for the whole recall impairment.

Adult↗

Memory development in learning disabled children: evidence from nonverbal tasks.

The purpose of the present study was to test the developmental lag hypothesis with learning disabled children on two and three dimensional nonverbal task. Twenty-two learning disabled boys in two age groups of 11 each were tested on a probe memory recall procedure. In contrast to generalization of a developmental lag hypothesis, age-equivalent recall in primacy and recency positions reflected patterns similar to those of normal children. Further, a developmental analysis of nonverbal recall revealed constant age-related differences. Results suggested the developmental memory lag interpretation has been confounded with learning disabled children's generalized verbal deficits.

Child↗

Imitation of hierarchical action structure by young children.

To provide the first systematic test of whether young children will spontaneously perceive and imitate hierarchical structure in complex actions, a task was devised in which a set of 16 elements can be modelled through either of two different, hierarchically organized strategies. Three-year-old children showed a strong and significant tendency to copy whichever of the two hierarchical approaches they witnessed an adult perform. Responses to an element absent in demonstrations, but present at test, showed that children did not merely copy the chain of events they had witnessed, but acquired hierarchically structured rules to which the new element was assimilated. Consistent with this finding, children did not copy specific sequences of actions at lower hierarchical levels.

Child Development↗

Effects of d-amphetamine and cocaine on strained ratio behavior in a repeated-acquisition task.

Pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors. When the fixed-ratio requirement for food presentation was five completions of the chain, d-amphetamine and cocaine disrupted the behavior. As the dose of each drug was increased, the overall response rate decreased, the overall accuracy was impaired (i,e., percent errors increased), and there was less within-session error reduction (acquisition). In contrast, when the fixed-ratio requirement was either 20 or 50 completions of the chain, certain doses of both drugs produced large increases in the overall response rate by eliminating the extended pausing (ratio strain) that was characteristic of the control sessions. These rate-increasing effects were accompanied by error-decreasing effects, both during acquisition and after the response chain had been acquired. Taken together, the results show that the effects of d-amphetamine and cocaine on behavior in a repeated-acquisition task can be modulated by manipulating the value of the fixed-ratio schedule maintaining the behavior.

Animals↗

Meaningfulness and isolation effect for normal and retarded subjects.

The aim of this study was to verify whether, in the normal and retarded subjects (aged 11.7 yr.), the isolation effect is less evidence the lower the meaningfulness of the material to be recalled. 12 groups were tested, six normal and six retarded, each of 25 subjects. The retardation was diagnosed with Raven's Progressive Matrix '38. Three series each of 9 CVC trigrams were used at 15--20%, 50--55% and 85--90% of associative value, respectively. Each trigram was exposed for 3 sec. As the level of meaningfulness increased so did the isolation effect for both normal and retarded subjects. For the retarded, however, the isolation effect only appears when the level of meaningfulness is very high.

Child↗

Primacy in causal strength judgments: the effect of initial evidence for generative versus inhibitory relationships.

The order in which people receive information has a substantial effect on subsequent judgment and inference. Our focus is on the order of covariation evidence in causal learning. The first experiment shows that the initial presentation of evidence suggesting a generative causal relationship (the joint presence or joint absence of cause and effect) leads to higher judged causal strength than does the initial presentation of evidence suggesting an inhibitory relationship (the presence of cause or effect in the absence of the other). Additional studies show that this primacy effect is unlikely to be due to fatigue or to an insufficient number of learning trials. These results are not readily explained by current contingency-based or associative theories of causal induction.

Adult↗

Individual differences in working memory capacity predict visual attention allocation.

To the extent that individual differences in working memory capacity (WMC) reflect differences in attention (Baddeley, 1993; Engle, Kane, & Tuholski, 1999), differences in WMC should predict performance on visual attention tasks. Individuals who scored in the upper and lower quartiles on the OSPAN working memory test performed a modification of Egly and Homa's (1984) selective attention task. In this task, the participants identified a central letter and localized a displaced letter flashed somewhere on one of three concentric rings. When the displaced letter occurred closer to fixation than the cue implied, high-WMC, but not low-WMC, individuals showed a cost in the letter localization task. This suggests that low-WMC participants allocated attention as a spotlight, whereas those with high WMC showed flexible allocation.

Attention↗

Evidence for implicit scaling in comparative judgment.

In two experiments, we examined the effects of manipulating the density of stimuli on comparison difficulty in a comparative judgment task. In Experiment 1, subjects was slower at judging the relative size of a pair when the members were adjacent items in the linear order than when the members were separated by items of intervening magnitudes. In Experiment 2, the advantage of choosing the larger rather than the smaller of two large stimuli (e.g., the congruity effect) increased when the linear order included many small items. In contrast, the advantage of choosing the smaller of two small items increased when the linear order included many large items. The applicability of the range-frequency theory (Parducci, 1965) to these results is discussed.

Attention↗

Animal test systems to study behavioral dysfunctions of neurodegenerative disorders.

The Eighth International Neurotoxicology Conference, Role of Toxicants in Neurological Disorders (1990), evaluated the evidence that chemical exposures may play a role in the development of neurodegenerative disorders. This article describes the major neurodegenerative disorders (Amyotrophic Lateral Sclerosis, Huntington disease, Parkinson disease, and Alzheimer disease) addressed at the conference, followed by a description of test systems or models developed to study behavioral aspects of these disorders in animals. However, due to the complexity of the disorders and the species in which they are found, fully-developed models in animals of neurodegenerative disorders are lacking. This suggests the need for a clear strategy for selecting behavioral tests in animals to study aspects of any neurodegenerative disorders. Such a strategy is here exemplified for Alzheimer disease (AD) as a prototypical neurodegenerative disorder. Since an animal model cannot provide the full range of effects of human neurodegenerative diseases, particularly AD which produces incompletely characterized cognitive deficits, a rodent model must at this time be drawn from multiple sources, including: (1) Tests currently used to identify in rodents deficits associated with AD; (2) tests to identify Alzheimer-related signs in patients; and, (3) tests that relate to theoretical constructs of human and animal cognition. A battery that draws from those sources could include tests of: (a) Spatial learning and memory (Morris Water Maze and Radial Arm Maze), (b) delayed recall match-to-sample; (c) serial response learning; and, (d) visual discrimination (e.g., vertical vs. horizontal stimuli). This battery will identify behavioral changes characteristic of early-, middle- and late-stage AD, afford the potential to relate the findings to theoretical constructs of cognition, and evaluate learning capabilities not previously studied in rodent models of neurodegenerative disorders.

Alzheimer Disease↗

Intellective functioning and strategy use in children with insulin-dependent diabetes mellitus.

The cognitive development of children with either early or late onset insulin-dependent diabetes mellitus (IDDM) was investigated with tasks measuring intellectual ability, memory, and academic progress. In addition, children's perceptions of their competence and parents' perspectives on family functioning and their children's behavior were compared. It was found that children with IDDM scored within the normal range on standardized measures of intelligence and academic performance but evidenced some school difficulties, as reflected in subscale performance as well as in their need of remedial education services. Further, evidence was found to suggest deficiencies in children's use of strategies to organize and recall information, particularly for those with early onset of disease. Children's perceived self-competencies and parents' reports of family functioning were strikingly similar across groups. However, parents of those children whose illness began prior to age 5 reported their children to have poor attention spans and difficulty completing tasks.

Achievement↗

Observational learning and the use of retrieval information during the second and third years.

The authors report 2 cross-sectional studies dealing with observationally derived acquisition of serial and sequentially coordinated activities in children between 12 and 30 months. In Study 1, greater improvements in activity occurred at every age beyond 12 months for modeling than for control groups, demonstrating age-related advances in ability to use modeling in connection with these action classes. However, significant gains did not imply complete reconstruction from memory, which resulted most typically for fewer than 50% of children. Moreover, when sequential tasks were subdivided on the basis of task demands, somewhat greater observationally derived change was found for the class of constrained tasks than for free-standing tasks. Study 2 concentrated on serial task performance and the use of massive retrieval cues in the form of assembled stationary displays, to test the efficacy of such cues in helping children reproduce the serial activities they had observed. Again, children who witnessed modeling were better at reproducing serial assemblies than control-group children. The use of retrieval information, however, was noticeably lacking as late as 22 months, whereas substantial gains were made over the next 6 months. The outcome was supported by exploratory processing results for the 2 ages. Increased use of the cues by 28 months appears to reflect important developments in awareness of the uses to be made of retrieval information, as well as success in its utilization.

Attention↗

A comparison of the effect of fluoxetine and trazodone on the cognitive functioning of depressed outpatients.

Tricyclic antidepressants with clinically significant amounts of anticholinergic activity can adversely affect memory and cognitive functioning. The study evaluated the effect of two non-anticholinergic antidepressants, fluoxetine and trazodone, on immediate and short-term memory in clinically depressed outpatients. The results of this study demonstrated that neither drug affected the depressed patients' cognitive skills as measured by the Guild memory test (digit span and paired associations) during their treatment and recovery. The only factor that was useful in predicting an improvement in cognitive functioning was the change in the measures of depression (Hamilton Rating Scale for Depression and Clinical Global Impression) with time.

Depressive Disorder↗

Short-term item memory in successive same-different discriminations.

Pigeons were tested in a successive same-different (S/D) discrimination procedure to examine the short-term memory for individual items in sequences of different or identical pictures. Item-by-item analyses of pecking behavior within single trials revealed this S/D discrimination emerged at the earliest possible point in the sequence--the presentation of the second item. Further, by comparing peck rates at points where different types of sequences diverged (e.g. ABA versus ABC), we determined that the pigeons remembered the first item for at least 4-8s and across one to two intervening items. These results indicate that this S/D discrimination was controlled by relational comparisons of pictorial content across memories of specific items, rather than the detection of low-level perceptual "transients" between items. A second experiment supported this conclusion by showing increased discrimination with longer first item viewing times, consistent with encoding of details about individual pictures. These findings further support a qualitative similarity among birds and primates in possessing a general capacity to judge certain types of stimulus relations, such as stimulus identity and difference. Implications for the temporal continuity of experience in animals are also considered.

Animals↗

Go - no go learning after frontal lobe lesions in humans.

48 patients with unilateral frontal or non-frontal cortical lesions were given a go - no go learning task. Patients with frontal lesions in either hemisphere took longer to learn the task and made more false "go" responses than control patients. They also, unlike controls, took longer to make in correct positive responses than correct positive ones. Medial frontal lesions were found to be particularly important in giving rise to poor performance on this task. It is suggested that this task is non-unitary in nature and that the medial area may be important for more than one ability.

Adult↗