Subject: Re: need MDS discussion From: Amit Gal <hobbit(at)PLUTO.MSCC.HUJI.AC.IL> Date: Tue, 5 Apr 2005 10:41:35 +0300hi, personally, i'm not fond of MDS techniques for modeling similarity ratings. as far as i experienced and read, similarity judgements tend to be too much context dependent (so sometimes the judgements you get for "a is similar to b" and "b is similar to a" are different, and it may be sensitive to "irrelevant options" and sensitive to the experimental methodology itself). you can read more about this in many of robert goldstone's papers on similarity for example you can look at: http://cognitrn.psych.indiana.edu/rgoldsto/pdfs/similarity2004.pdf however, for timbre, there are some known applications of mds for example: Grey, J. M. (1977). Multidimensional perceptual scaling of musical timbres. Journal of the Acoustical Society of America, 61, 1270-1277. some of stephen mcAdams researches on musical timbre also use MDS. stephen mcAdams told me that forthe specific case of timbre most of the complexities of similarity do not occur, and that he thinks it is safe to use it. however, i didn't see evidence on that, so i can't comment whether i believe it or not. mathematically speaking, the concept of MDS is a tricky one, as there are many ways to play with the number of dimensions without distorting too much the original "distances" (that came from examinees responses). this means that there is no one "true" answer even about the number of dimensions needed to model the results. on the other hand it does give you a simple graphical way to understand your results and interpret them. so if you ask me, i would advise you to use mds with lots of caution. hope this helps (and not too discouraging) amit. Quoting beaucham <beaucham(at)MANFRED.MUSIC.UIUC.EDU>: > > We are looking into doing a multidimensional scaling test > on a group of sounds and would like to read about the pros > and cons of using subject rating of the similarity of pairs > of sounds (e.g., on a 0 to 10 scale) vs. judging which of > two pairs presented in rapid succession is most similar. > Please let me know if you know of a reference which discusses > this point. > > Jim Beauchamp > Univ. of Illinois at Urbana-Champaign > jwbeauch(at)uiuc.edu > ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.