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Re: Usual settings for the transformed up-down procedure

Tooting my own aging horn:

Marvit, P., Florentine, M., and Buus, S. (2003). "A comparison of psychophysical procedures for level-discrimination thresholds," Journal of the Acoustical Society of America 113, 3348-3361.

My bottom line interpretation from that study, apart from the specific procedures: More samples/estimates may provide better accuracy for threshold estimates, rather than trying to be more precise in a single session. Session-to-session (day-to-day) variance is much larger than within session (i.e., during any particular track). Thus, taking many "imprecise" but short estimates gives better overall results than a few very long (e.g., interleaved) but supposedly precise measurements.

Personally, I also like the algorithms developed by Chris Kaernbach, who graciously outlined them in a prior message. Of course, there are now large numbers of adaptive procedures from which to choose. The old 2-down, 1-up has the greatest virtue in simplicity of understanding and implementation, but is far from optimal in practicaly application.

Chris' message had an important point: Making the procedure easy and comfortable for your subjects will do more for your data than optimizing theoretical efficiency. His "I don't know" response works well in that regard, in addition to providing computational data. I've found many subjects who really liked working at P(correct) 85% (or more) and got quite anxious at 71%. Likewise, my subjects generally liked short runs MUCH more than long ones.

Good luck!

: Peter Marvit, PhD
:<pmarvit at gmail dot com OR pmarvit at psyc dot umd dot edu>
: Psychology Department, University of Maryland, College Park
: College Park, MD 20742
: (lab) 301-405-5940    (fax) 301-314-9566

On Fri, May 29, 2009 at 10:08 AM, Sylvain BUSSON <Sylvain.BUSSON@xxxxxxxxxx> wrote:
The adaptive up-dow procedure offers many benefits over methode of constants.
Does anyone know if one of theses benefits is related to the number of repetition for each condition ?
In other words, can we get a reliable threshold estimate with only 3 repetitions (3 tracks for the same condition)  ?