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Psychophysical studies with infants or with patients often are unable to use pilot data, training, or large numbers of trials. To evaluate threshold estimates under these conditions, computer simulations of experiments with small numbers of trials were performed by using psychometric functions based on a model of two types of noise: stimulus-related noise (affecting slope) and extraneous noise (affecting upper asymptote). Threshold estimates were biased and imprecise when extraneous noise was high, as were the estimates of extraneous noise. Strategies were developed for rejecting data sets as too noisy for unbiased and precise threshold estimation; these strategies were most successful when extraneous noise was low for most of the data sets. An analysis of 1,026 data sets from visual function tests of infants and toddlers showed that extraneous noise is often considerable, that experimental paradigms can be developed that minimize extraneous noise, and that data analysis that does not consider the effects of extraneous noise may underestimate test-retest reliability and overestimate interocular differences. 相似文献
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The purpose of these two experiments was to determine (a) whether young children can be responsive to caloric density cues in regulating their food intake, (b) whether such cues can be associatively conditioned to organoleptic cues in foods, and (c) to obtain evidence regarding which of the many cues available are involved as conditioned stimuli. In Experiment 1 participants were eighteen 3- to 5-year-old children, who were seen for a series of pairs of conditioning trials, followed by extinction test trials. Each trial consisted of a two-part snack: approximately 100 ml of a pudding preload (chocolate or vanilla; high or low caloric density) followed after a delay by ad-lib consumption of snack foods (cookies and crackers). In extinction trials, flavors previously paired with high- or low-caloric density preloads during conditioning were presented in isocaloric intermediate density preloads. Results indicated that 14 of 18 children showed unconditioned caloric compensation on the first pair of conditioning trials; 16 of 18 children showed compensation following the second pair of trials, and 12 of these 16 subjects continued to show this consumption pattern during extinction. Consumption was significantly greater following the low calorie paired flavor than following the high calorie paired flavor during extinction. Experiment 2 (N = 10) replicated these findings, and uncorrelating preload and snack food flavors indicated that flavor cues in the preloads can serve as conditioned stimuli. Children showed both initial responsiveness to caloric density and evidence for associative conditioning of food cues to the physiological consequences of eating. These results provide initial evidence for a mechanism allowing the child to learn to anticipate the caloric consequences of familiar foods and regulate food intake accordingly. 相似文献