Subject: Usual settings for the transformed up-down procedure From: Massimo Grassi <massimo.grassi@xxxxxxxx> Date: Wed, 20 May 2009 16:03:09 +0200 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Dear list members (and transformed up-down user in particular), we are extending our MLP software (http://www.psy.unipd.it/~grassi/mlp.html) to the transformed up-down adaptive procedure so the user of our software can decide to run a given threshold-experiment with either the maximum likelihood procedure or the transformed up-down (wow! what a fun!). We are now working on the software and facing the first problem: what are the "traditional" settings for the transformed up-down? In brief: - how many "downs"? - how many reversals before stopping the procedure? - how many reversal with a small step-size and how many with a large one? - how many step-sizes? - what's the (is there any) "usual" ratio between small and large step-size? - how to calculate the subject's threshold? Here the traditional rules base on my own reading: - Number of "downs". I found only studies using the 2(or 3)-down 1-up. No study using the 4-down (or higher) 1-up rule. Furthermore, no study using the 1-down, 2/3/4...-up. - Reversals and step-size. So far I found that people tend to use two step sizes only (e.g., factor 2 and factor 2^(1/2), i.e., sqrt(2)) and to run 4 reversals with the large step size and 8 (or 12) reversals with the small step size. - For the threshold calculation I found that it is usually calculated on the last 8 (or 12) reversals points of a given block. Moreover, I found that people calculate indifferently arithmetic, geometric mean or median. I'm particularly interested in exceptions to the "traditional rules" I found: we want to include these exceptions to our software. Thank you in advance for the help you can provide, m