To me it looks like there is a 6 frame spread (from #6 to #12) that shows the reaction time. #6 being the input of stimulus, to #12 being the reaction to the stimulus. 6 frame = 200ms, which is the statistical middle of the curve (no offense):

http://www.humanbenchmark.com/tests/...time/stats.php

also, http://en.wikipedia.org/wiki/Reaction_time