[DMDX] Re: questions about COT Thanks, Jonathan! I will run the file again and see what the time difference is. shiaohui ----- Original Message -----  From: "j.c.f."  To:  Sent: Saturday, February 04, 2006 4:34 PM Subject: [DMDX] Re: questions about COT > At 01:54 AM 2/4/2006 -0700, you wrote: >>I knew it today that I should have included 101 as an item, and that line  >>should look like this: >> >>     +101 *  %1 /  %1/ "READY" /;" >> >>and the azk file should start with something like below: >> >>     Item 101, COT 0.000 (and some RT) >>     Item 1046, COT 13513.02 (and some RT) >> >> >>I will correct this in my future script, but I want to understand my error  >>better, so here are the questions: >> >>In my experiment, the fMRI scanner won't start collecting data until 12  >>seconds after the spacebar of the computer is hit (to start DMDX).  Since  >>SOAs (relative to scanner data collection) instead of COTs are needed in  >>image processing, the usual way to translate a COT value to an SOA value  >>is to subtract 12 seconds from each COT value. >> >>1) Where in the line does the scanner start?    %1 /  %1/  >>"READY" /; > >   Probably the with the . > >> >>2) Except for the first item, is my azk file really different from the  >>"should-be" azk file? > >   Dunno, I don't remember details of everything I've ever done.  People  > that use  the scanner regularly are going to have a better idea than I am. > >> >>The following two questions are related to Question 1: >> >>3) The presentation computer I used has a refresh rate of 16.58 ms, so I  >>actually put a little bit more than 12 seconds on item 101.  I guess the  >>scanner had started collecting data before the "COT=0.00" time point in my  >>azk file.  Am I right? > >   If what you say is so, yes. > >> >>4) If I still want to use the data that I collected (I collected two pilot  >>subjects with this script), should I correct my COTs?  I.e., should I add  >>5.92 ms, 4.92 ms, or 3.92 ms to each of the COT value, depending on when  >>the scanner is started?  (I got the value of 5.92 ms by subtracting 12000  >>ms from 724x16.58 (= 12003.92) plus two %1's). > >   I would run the file again with a clockon in the first item and see what  > it is by item 1046 and add that to clock on times in the first run. > >                                                /"\\ >  -jonathan (j.c.f.)                            \\ / >                                                 X >     ASCII RIBBON CAMPAIGN - AGAINST HTML MAIL  / \\ > > If frogs had wings, they wouldn't be bouncing around on their bums. > > > ==================================================================== >   Send mail to DMDX-request@psy1.psych.arizona.edu with the word >  'unsubscribe' by itself with no quotes in the body of the email >  to be removed from the list.  The list archive is available here: >          http://psy1.psych.arizona.edu/cgi-bin/DMDX/thread > ====================================================================