Showing papers by "David L. Strayer published in 1994"

Aging and Inhibition: Beyond a Unitary View of Inhibitory Processing in Attention

Abstract: The authors examined the question of whether a decrease in the efficiency of inhibitory processing with aging is a general phenomenon. Thirty elderly and 32 young adults performed a series of tasks from which the authors could extract measures of inhibitory function. The tasks and task components included response compatibility, negative priming, stopping, spatial precuing, Wisconsin Card Sorting Test (WCST), and the Cognitive Failures Questionnaire (CFQ). Only limited evidence for age-related differences in inhibitory function was obtained. Old adults had more difficulty than young adults in stopping an overt response and adopting new rules in a categorization task. However, elderly and young adults produced equivalent negative priming effects, response compatibility effects, spatial precuing effects, and self-reported cognitive failures. The findings are discussed in terms of the relationship between aging, inhibitory processes, and neuroanatomical and physiological function.

Executive function abilities in autism and Tourette Syndrome: An information processing approach

Abstract: This study used information processing paradigms to provide a detailed examination of executive function abilities in autism. The performance of non-retarded autistic children was compared with that of two matched control groups, one with Tourette Syndrome and the other developmentally normal. Autistic subjects performed as well as controls on tasks requiring global-local processing and inhibition of neutral responses. In contrast to both control groups, however, the autistic sample was significantly impaired on a measure of cognitive flexibility. The performance of children with Tourette Syndrome did not differ from that of normal controls on any task. These results refine our knowledge about executive dysfunction in autism and suggest a new conceptual framework and general method for investigating the cognitive underpinnings of neurodevelopmental disorders.

Distribution, abundance, and roles of freshwater clams (Bivalvia, Unionidae) in the freshwater tidal Hudson River

Abstract: SUMMARY 1. An extensive series of PONAR grabs was used to determine the distribution and abundance of unionid clams in the freshwater tidal Hudson River. 2. The five species of unionids collected were distributed very unevenly within the river. Mean river-wide density and biomass of unionids were 8.0m−2 and 6.2 g DM m−2 (shell-free)., respectively. 3. The environmental variables that we measured (water depth, distance from shore, sediment granulometry and organic content, presence or absence of macrophytes, and the chlorophyll a and particulate organic matter content of the water) explained little of the variation in abundance of unionids. 4. The distributions of the various species of clams did not differ significantly with respect to the environmental variables measured. 5. We estimate that unionids filter a significant amount of water (0.14m3 m−2 day−1, on average) in the Hudson River estuary, roughly equivalent in magnitude to downstream flushing. 6. We project that unionids will serve as a major substratum for the settlement of the zebra mussel (Dreissena polymorpha), which is now invading the estuary. We emphasize that unionids may play important non-trophic roles in large river ecosystems.

Strategies and automaticity. I: Basic findings and conceptual framework

Abstract: The contributions of strategic and data-driven factors to skilled performance were evaluated by manipulating the predictability of the class of stimuli used in a memory search task. In Experiment 1, when consistent mapping (CM) and varied mapping (VM) conditions were blocked, large performance differences were observed; however, when CM and VM trials were mixed, performance differences were reduced. In Experiment 2, mixed training led to a less skilled performance than blocked training. Moreover, transfer conditions revealed a critical interval for learning to adopt and deploy differential response strategies. Experiment 3 demonstrated that the differential response strategies were not stimulus specific

Aging and skill acquisition: learning-performance distinctions.

Abstract: This research examined the hypothesis that a conservative response bias in older persons interferes with the acquisition and mastery of cognitive skill. Twenty younger and 20 older Ss performed both consistent mapping and varied mapping versions of a memory search task. Half of the Ss in each group performed under speed stress instructions, whereas the remaining Ss performed under accuracy stress instructions. Older Ss exhibited less skilled performance than did younger Ss. A power function analysis attributed this to both age-related differences in the rate of associative learning and differences in asymptotic levels of performance. These results are at odds with A. D. Fisk and W. A. Roger's (1991) hypothesis that age-related differences in automatization do not occur in memory search tasks. Results are interpreted in terms of a learning vs. performance distinction.

Strategies and automaticity: II. Dynamic aspects of strategy adjustment.

Abstract: The temporal dynamics of strategic adjustment of response criteria were examined by comparing performance in blocked conditions, in which all stimulus-response mappings were either consistent (CM) or varied (VM), to performance in mixed conditions, in which CM and VM items were presented in the same block of trials. We examined the degree of flexibility that subjects exhibit in deploying differential response strategies. Surprisingly, Ss were unable to use a variety of informative pre-cues to rapidly shift between response strategies associated with automatic (CM) and nonautomatic (VM) processing. However, an analysis of sequential dependencies indicated that repetition of stimuli from the same class (CM vs. VM) gradually led to shifts in response strategies

Diacyclops dimorphus, a New Species of Copepod from Florida, with Comments on Morphology of Interstitial Cyclopine Cyclopoids

Abstract: Diacyclops dimorphus, new species, was collected from clean sand sediments of the Blackwater River, State of Florida, USA. The new species differs from congeners in that the female has all rami of the swimming legs biarticulate, but the male has most rami biarticulate and the leg 4 exopodite triarticulate. Only two other species of Diacyclops show comparable extreme reduction of the swimming legs. These are Diacyclops virginianus and Diacyclops trajani (a new name proposed for Speocyclops minutissimus sensu Petkovski 1954). The swimming leg articulation patterns of all species of Diacyclops are reviewed. This is the first report of consistent sexual dimorphism in swimming leg articulation in Diacyclops. Sexual dimorphism in the swimming legs rarely occurs in the subfamily Cyclopinae. We suggest that preferential reduction in endopodites of posterior legs of smaller cyclopines allows the female genital double somite to remain relatively large. Many interstitial cyclopine copepods possess distinctive morpho...

Body size and abundance of benthic animals in Mirror Lake, New Hampshire

Abstract: SUMMARY 1. There is a strong negative correlation between body mass and population density for 192 species from the zoobenthos of Mirror Lake, a small, oligotrophic lake. This correlation spans seven—nine orders of magnitude in body mass. 2. The slopes of both the regression and the upper bound on the distribution of data points are significantly shallower than -0.75, the slope that has been suggested to imply that metabolic constraints limit animal abundance. 3. The regressions for individual taxonomic groups (i.e. classes, phyla) do not conform closely to the overall regression line. 4. It is suggested that metabolic constraints on community structure need not be expressed by a slope of -0.75 for regressions (or upper bounds) on body mass—abundance functions.