slopes among subjects lends credibility to the method as a procedure to examine individuals.
The interactive training program for making numerical introspections of subjective magnitude has been shown as a robust method for studying the perceptual scales of individuals. As an adjunct to other tasks (e.g., scaling various complex and physically unmeasurable properties), it permits us to screen subjects who are unable to perform the required task.
Other advantages accrue to this procedure. Outliers are minimized through the use of feedback and appropriate queries about aberrant judgments. This yields data that probably reflect more clearly the intended responses of the subject. The method improves traditional procedures in at least two ways: It is more robust because each judgment is independent of all others, and so sequential bias cannot creep in to induce departures from the underlying percepts. Furthermore, by reducing intertrial dependencies the commonly reported compounding or cumulation of error is avoided. Second, the use of ratios as a representation of both stimuli and responses defeats complaints about the legitimacy of the response representation as a scale of magnitude with no underlying theoretical support ( Krantz, 1972; Shepard, 1981).
Portions of the work reported here were supported by a grant from the National Aeronautics and Space Administration. All magnetic materials, tape, cassettes, and disks, were provided through the generosity of the Maxell Corporation of America.
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