[DMDX] RT measurement - sanity check please I would like to ask for some indulgance and a sanity check (DMDX script check actually). I am not sure if my script is doing precisely what I intended because the resulting data smells fishy. Below is one line from an item file which I have broken up into conceptual chunks here: (chunk 1 - wait interstimulus interval with fixation cross) Item #23, display the character "+" for 223 ticks (chunk 2 - display fixation and cue) display the characters "+" and "O" for 13 ticks (~200 milliseconds) and start the RT clock with a timeout of 2700 milliseconds (chunk 3 - display fix)  display a "+" alone for 49 ticks (800 ms) (chunk 4 - display fix and target)  target = "<<<<<<" wait for response or end of timeout before moving to next item.)   +23      "+"  /     "+" ,     "O" *   /     "+" /    "+" ,     ">>>>>" ; Now, the reaction time I really want to measure is from the onset of the target presentation (chunk 4), but to catch premature responses to the presentation of the cue (in chunk 2), I start the RT clock with the cue onset. So, to calculate the actual valid RT, I take the raw RT measurement and subtract 13 + 49 ticks (in milliseconds). The problem is that the data does not look right.  Is it possible that the RT clock is measuring from the start of chunk 3? Thanks a million! - Derek Derek Eder BagaregÃ¥rdsgatan 3E, nr 134 SE 416 70 GÃ¶teborg (Gothenburg) Sverige (Sweden) +46 (031) 25 97 07 (home) +46 0709 721 283 (mobil) email:     derek_eder@yahoo.com web page:  www.derek-eder.org "Forgiveness means giving up any hope for a better past" - after Gil Fronsdal __________________________________________________ Do You Yahoo!? Tired of spam?  Yahoo! Mail has the best spam protection around  http://mail.yahoo.com