Copyright 2012 Aileen M. Echiverri-Cohen - University of Washington

the letters and ignore the numbers from a stream presented in rapid succession. Following the
stream of letters and numbers, participants entered the target letters on the keyboard. If no
second target was present, participants pressed a key labeled 'NO' on the keyboard to ensure that
participants were always entering two responses. Participants started with a practice block of six
trials. Participants were given a 1 min break halfway through the AB task.
For the PPI task, participants were oriented to psychophysiological monitoring
procedures. Next, physiological monitoring sensors were attached. Participants heard soft and
loud sounds that were intermittently delivered through the headphones. To help improve
participant attention (Ornitz et al., 1989), participants viewed a silent video that showed various
scenic panoramas, which ran for the duration of the task.
Following the assessment at pre-treatment, participants were paid $20/hour for their time.
AB and PPI were repeated again at post-treatment using the same counterbalancing order. At the
end of this visit, participants were debriefed on the study purpose and paid $20/hour for their
participation.
Data Reduction
AB. To assess the main AB effect, the percent accuracy of T2 identification was
calculated across lags on trials in which T1 was correctly identified (Raymond, Shapiro, &
Arnell, 1992), reflecting the probability of correct T2 identification given accurate identification
of T1. Accurate identification was defined as correct responding with the correct letters and
order in the RSVP out of number of trials in the lag. For example, if T1 is "A" and T2 is "J", the
correct responses are "A then J" and not "J then A".
PPI. The EMG responses in each type of trial were averaged across the 40 trials. Startle
trials preceded by prepulses reflect a reduction in magnitude produced by a prepulse, with startle
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