Evaluation of Ratio Scaling Methods
In the methods of magnitude estimation and magnitude production, numerical estimations of sensation magnitude are obtained for a series of stimuli of varied intensity. The objective of the experiment is to establish precisely the functional relationship between stimulus intensity and sensation intensity. To accomplish this objective, valid measurements must be made of both stimulus and sensation intensity. It is important that the validity of both stimulus measurements and psychophysical judgments of sensation intensity be experimentally demonstrated. This has traditionally taken the form of demonstrations of additivity and transitivity of measurements.
Techniques of physical measurement, when correctly used, generally produce valid measurements of the stimulus. It has been the tradition in physical science that any new method of measurement, in order to become widely accepted, must withstand vigorous tests of its validity. One test of validity requires that the measurements produced by a new method be in agreement with those produced by another method that is known to be valid. If a method with established validity does not already exist, other procedures must be used to test the validity of the new method. One such test is to evaluate the additivity of the measurements produced