PEBL Continuous Performance Task (PCPT), a continuous
performance task modeled after a set of classic paradigms, and implements 
a version of Conner's CPT.  This is a vigilance task, which takes approx 14
minutes to complete.  360 letters approx 1 inch in size are presented
one at a time.  Participant must respond by pressing the space bar to
all stimuli except the X.
