Peter H. Schönemann
Professor Emeritus • Department of Psychological Sciences • Purdue University
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Note: numbers in brackets refer to Publications list.

Multidimensional Scaling

Some early work on Thurstonian scaling  [5, 10], Guttman's simplex theory [7], and Coombsian metric multidimensional unfolding [9].  An algebraic solution for Horan's subjective metrics model (which underlies "INDSCAL" [15]) was subsequently extended into a computationally efficient and robust scaling algorithm (COSPA, [25, 29]).  Later  [9] was extended (with Wang) into a multidimensional scaling model for preference data that combines the Bradley-Terry-Luce model with  Coombs' unfolding model  [14, 19]. A common characteristic all these metric MDS models share is that they all have exact algebraic solutions and are, at least in principle, testable [35, 39].

Later  empirical work  with similarity data on rectangles followed up on Krantz and Tversky's (1970) lead [36, 37]).  On closer scrutiny we found that dissimilarity ratings often  violate some basic assumptions required by the conventional metric models, notably  the Archimedean axiom, which underlies all Minkowski metrics, in particular, the euclidean and the city-block metric [38, 41, 42, 46, 48, 59, 73].

More generally, such findings cast doubt on the research promise of prepackaged scaling programs that ignore the actual judgement behavior of the subjects. In hindsight, the few nontrivial insights produced during the MDS craze of the 70s seem to have been  mostly artifacts [36, 38, 59].

Naively, one might think that  both scaling and test theory ought to relate to measurement theory  in some way since all three profess to be concerned with the problem of assigning numbers to objects or subjects. Our earlier, still relatively upbeat thoughts on these issues  are summarized in [33, with I. Borg].  However, as  time went on, and the anticipated empirical support of axiomatic measurment theories  never materialized,  we found it increasingly harder to maintain our earlier optimism about the prospective utility of such abstract theories. Eventually, this scepticism  extended to mathematics more generally as a tool for solving non-ficticious problems  in psychology [73].