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Biomedical subjects

D W Curtis

Publications and source records attributed to D W Curtis.

15 recordsLinked to original sources
PubMed1985

Ordinal properties of perceived average duration: simultaneous and sequential presentations.

When a subject evaluates the duration of two simultaneous events, the perceived durations are combined in a nonlinear manner, whereas comparable evaluations of successive events yield linear combinations. Fifty-four subjects rated average durations of pairs of time intervals ranging from 0.5 s to 10.0 s. The intervals making up a pair were presented successively and simultaneously on separate occasions within the same presentation sequence. The order of data was consistent with models previously proposed for perceived average duration. A nonmetric analysis of the combined ordinal data from both conditions yielded a single set of measures of perceived duration with ratio-scale properties. The common scale for the two conditions is consistent with differences in results from simultaneous and successive monitoring of time intervals, stemming from differences in the way duration information is combined rather than how it is perceived. the derived scale is related to physical time by a power function with a 1.06 exponent.

Adolescent↗
PubMed1981

Subjective ratios and differences in perceived heaviness.

In previous studies, judgments of ratios and differences in subjective magnitude have yielded similar orders, consistent with a hypothesis that a single perceived relation underlies both judgment tasks. In the present research, 15 subjects estimated heaviness differences between 28 pairs of eight weights and each of 8 groups of 10 subjects evaluated heaviness ratios of eight variable stimuli with respect to a different standard stimulus. Presenting stimuli that were equally spaced on a cube-root scale of weight enhanced expected ordinal discrepancies between ratio and difference estimates, and employing independent groups for each standard stimulus in ratio estimation eliminated a possible bias due to varying standards within the presentation sequence. Differences in orders of ratio and difference estimates together with differences in scales obtained from non-metric analyses in terms of a difference model indicated that the judgments were based on two perceived relations that are ordinally consistent with arithmetic operations of ratios and differences. A ratio scale of heaviness was derived from the combined orders of subjective ratios and differences.

Discrimination Learning↗
PubMed1980

Ordinal properties of subjective ratios and differences: Comment on Veit.

Because nonmetric analyses of judged ratios and differences in sensory magnitude have yielded similar scales, some investigators have concluded that a single perceived relation underlies both judgment tasks. Issues rasied by this interpretation are considered in this article. Simulated data based on the assumption that subjects evaluate both perceived relations were computed for stimulus values used by Veit to investigate judgments of ratios and differences in grayness. A nonmetric analysis of both sets of simulated data in terms of a difference model yielded a solution such that each set of data was a weak monotonic transformation of the model's values, and the scale values were approximately linear with those obtained by Veit from empirical data. This result leaves open the question of whether one or two perceived relations underly the data. Ordinal properties of ratios and differences for a finite set are discussed together with their relation to systematic biases in psychophysical judgment tasks.

Color Perception↗
PubMed1978

Binocular processing of brightness information: a vector-sum model.

The relation between monocular and binocular brightness was examined. Clear evidence was found that the interaction between visual channels in binocular processing of brightness information implicates both an apparent averaging of monocular brightness when they are grossly different and a partial summation when they approach equality. A vector-sum model is shown to predict these properties. A nonmetric method was used to fit such a model to data from three experiments in each of which 15 subjects estimated brightness of binocularly fused targets. Magnitude estimation was used in two experiments, and cateogry ratings were obtained in the third experiment. When it was assumed only that subjects' responses were monotone with perceived brightness, estimates of the model's parameters from the data of the three experiments were almost identical, indicating that results from magnitude estimati;n and category rating can converge once nonlinear response functions are eliminated.

Discrimination, Psychological↗
PubMed1977

Matching of normally oriented and mirrored words by good and poor readers.

10 good and 10 poor Grade 6 readers judged tachistoscopically presented word pairs to be "same" or "different" when the words making up the pairs were both normally oriented, both mirrored, or one was oriented and the other was mirrored. Good readers made fewer errors than poor readers on normally oriented "same" pairs but showed no advantage on other configurations. Poor readers were more accurate in detecting mismatches than good readers. These results were discussed in terms of the mechanism that may have been implicated.

Child↗
PubMedDate not supplied

Student dental hygienists' work values: a measure of an emerging profession?

The purpose of this study was to compare the work values of students in the School of Dental Hygiene and the Faculty of Dentistry at the University of Manitoba, Canada, both with each other, and with national sample of Canadian practitioners in both fields. The study was an outgrowth of a larger study measuring the work values of graduating students in six faculties selected to represent the occupational classification system of John Holland. The English version of the Canadian form of the Values Scale which measures 20 work and life values, was used in this study. Differences in values found between the student hygienists and practitioners in both dentistry and dental hygiene may indicate a growing desire for professional status by dental hygienists. Value differences found between practising dentists and hygienists may reflect a traditional hierarchical relationship between these occupations. Limitations of the study and future research questions are discussed.

Adult↗