On the use of "calibration equations" in perception research.

Gogel's procedure of using "calibration equations" to obtain reports of perceived distance which are at least partially independent of individual differences in response bias, was examined. The procedure involves determining the relationship between reported and physical distances in a full-cue viewing situation. By making four assumptions, this equation can be used to "calibrate" responses gathered from other situations in which perceived distances are under investigation. In the present experiment, both verbal and string-pull measures of perceived distance were obtained for several objects under reduced viewing conditions. Calibration equations were determined for each response measure in a full-cue setting. The usefulness of the calibration technique was tested by comparing the differences between the two response measures for each object seen in reduced viewing, both before and after the application of the calibration procedure. The results indicated that, consistent with the usefulness of the calibration technique, group differences between the measures were almost always decreased by the procedure. However, no general improvement in the agreement of the measures was found when the data were examined on an individual basis. From the results, a modification of the method of calculating calibration equations was suggested that might increase its usefulness by simplifying the arithmetic operations required for the procedure.