On the "absoluteness" of category and magnitude scales of pain.

The concept of "absolute scaling" (Zwislocki & Goodman, 1980) implies that direct judgments of sensory magnitude not only reflect the relative positions of the stimuli being judged, but also permit us to assess level differences in sensation. In order to explore this notion for different scaling methods, in the present investigation we compared magnitude estimation with category partitioning, a verbally anchored categorization procedure, in scaling painful pressure stimuli covering different intensity ranges. The results indicate that when the same stimulus range was presented after 1 week, both methods appeared to be highly reliable, with category partitioning faring somewhat better than magnitude estimation. When the stimulus range was unobtrusively changed between sessions, both methods reflected the within-subjects shift in absolute level. When two different sets of subjects judged the slightly different stimulus ranges, both methods resulted in scale values consistent with absolute scaling, though only category partitioning was sensitive enough to differentiate the two stimulus ranges. The results are discussed in the context of different possibilities of anchoring direct scaling methods in order to obtain "absolute" level information.