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Biomedical subjects

L B Smith

Publications and source records attributed to L B Smith.

At least 73 records · Page 4Linked to original sources
PubMed1979

Accessing similarity and dimensional relations: effects of integrality and separability on the discovery of complex concepts.

A series of studies investigated how stimulus integrality and separability impact the cognitive accessibility of similarity and dimensional relations. A good deal of previous work has established that stimulus integrality and separability differentially determine perception; here, the question is whether they also have differential effects on conception. Are the principles that govern perception also principles that can be readily discovered in concept learning tasks? Is a similarity-based rule especially easy to abstract from integral stimuli and a dimensionally-based rule especially easy to abstract from separable stimuli? In Experiments 1 and 2, we measured the relative ease with which the two types of rules (similarity and dimensional) are discovered by adults with the two types of stimuli (integral and separable). In experiment 1, the two rules were made redundant and we asked which rule the subjects learned. In Experiment 2, one rule was made relevant and the other irrelevant, and we compared relative speeds of learning. The results from the studies led us to conclude (a) that dimensionally based rules are more accessible from separable than from integral stimuli; (b) that similarity-based rules are more accessible from integral than from separable stimul; and (c) that, in general, subjects have a bias to access dimensional relations in this type of task. Experiment 3 pursued an additional suggestion from Experiments 1 and 2 that the dimensional relations within integral stimuli are sometimes accessible, more so when larger interstimulus differences are encountered. In confirmation, Experiment 3 demonstrated that adult subjects are more successful in applying a dimensional rule to pairs of integral stimuli that differ by a small amount if they also have exposure to pairs of integral stimuli that differ by a large amount. In a later discussion, it was argued that such a finding is consistent with the notion that the "dimensions" of integral stimuli are merely arbitrary directions in the integral stimulus space, and some relevant pilot data to that effect were presented. Finally, Experiment 4 took up a developmental issue. Young children have sometimes produced perceptual responses governed by similarity relations when presented with stimuli that are separable for adults. Will they more readily access similarity-based or dimensionally-based relations from such stimuli in the concept learning tasks here? The results showed that both kindergarteners and fifth graders more readily access the dimensional relations. A final discussion integrated the findings from the several experiments, taking up the following issues: (a) the relation between the perception and the conception of stimulus relations and (b) the nonprimacy of the dimensional axes in the integral stimulus space.

Adult↗
PubMed1979

Zinc deficiency in the West of Scotland? A dietary intake study.

1. The intake of zinc in the West of Scotland was determined by atomic absorption spectrometry, in ninety-six items of food which make up the local standard diet for 1 week. 2. The diet contained less Zn than the recommended daily allowance ((US) National Academy of Sciences, 1974). This finding either indicates the need for a revision of the suggested allowances or suggests that a change of diet is necessary. 3. The change could be made simply by the substitution of wholemeal flour for white flour. Other changes in diet were considered but they were unlikely to be acceptable. Even with changes the requirement of pregnant or lactating women would not be met. If the recommended allowances are valid these women must be deficient in Zn.

Adult↗
PubMed1979

Perceptual development and category generalization.

This work is concerned with developmental changes in the structure of classifications. The central claim is that young children's undifferentiated perceptions of complex stimuli are highly structured by wholistic similarity whereas older children's perceptions are structured by component dimensions. It is shown in 2 experiments that young children systematically and spontaneously generalize a category if it is well organized by overall similarity but not if it is organized by a criterial dimension. Older children, on the other hand, spontaneously apprehend and extend a category by its dimensional structure. The third experiment was designed to test the hypothesis that criterial property categories are preferred in classification tasks requiring the explicit discovery of a general rule. It was found that younger children's attention to the dimensional relations within a category increases under rule-discovery instructions, although they still have difficulty ignoring wholistic similarity relations. The trend from similarity to dimensional classification is discussed in the context of Piagetian classification tasks and family-resemblance accounts of natural categories.

Child↗
PubMed1977

Effect of dietary amino acids, casein, and soybean trypsin inhibitor on pancreatic protein secretion in rats.

Pancreatic enzyme output in response to various purified diets was studied in rats surgically prepared so that pancreatic secretion could be continuously collected, assayed and returned to the intestine. Intraduodenal infusion of phenylalanine and tryptophan alone did not stimulate secretion. Diets containing phenylalanine, tryptophan, a mixture of amino acids, or hydroxyzed casein, fed intragastrically, evoked a small pancreatic response that was similar to the response to a protein-free diet. intragastric infusion of a diet containing 18% casein stimulated a large initial secretion of enzyme that remained elevated throughout the 5.5 hour experiment. Addition of soybean trypsin inhibitor (SBTI) to the diet increased the pancreatic response over that due to dietary casein alone. When pancreatic juice was diverted from the intestine, the large pancreatic responses to casein or to casein + SBTI were greatly reduced and the response was similar to that of the protein-free diet.

Amino Acids↗
PubMed1975

Diseases of the colon and rectum in Bolivia.

A review of the surgical and autopsy records from two general hospitals in La Paz, Bolivia, discloses an incidence of colon and rectal disease, excluding hemorrhoids, of 0.6 per cent (138 of 22,361 surgical cases) and 2.5 per cent (16 of 640 consecutive autopsies). Acquired megacolon complicated by volvulus represented more than half of all cases in the surgical series. Ulcerative colitis, diverticular disease, and neoplastic polyps represented less than 10 per cent of the cases of colonic disease. Only ten cases of carcinoma of the colon were seen, whereas five cases of granulomatous colitis or ileocolitis were detected in the same surgical material. Among sixty-four lesions of the rectum, so-called retention polyps accounted for 54.5 per cent of the cases, with carcinoma next in frequency (25 per cent), and the remainder being different varieties of inflammatory conditions. In the autopsy material almost half of the cases were infectious conditions, followed by congenital malformations and complicated acquired megacolon. No case of diverticular disease of the colon or neoplastic polyps was seen, and there was only one case of cancer of the large bowel. Because of the high incidence of acquired megacolon and the low incidence of cancer, ulcerative colitis, adenomatous polyps, and diverticular disease of the colon, possible etiopathogenic factors of these conditions are discussed in comparison with their incidence in other developed and developing countries of the world.

Altitude↗