75
target tone indicated that nothing would occur during the 6
second interval. Autonomic measures of arousal (HR, SCR)
and facial EMG measures were obtained. The order of the
anticipatory anxiety task and the anticipatory reward tasks
was counterbalanced across subjects in each group.
Stimuli and Apparatus
The electrical stimuli was delivered by a Grass S88
Stimulator and Isolation Unit. A Zenith Data Systems AT
clone computer was programmed to deliver one high tone
(usually 800 or 1000 Hz) as a warning stimulus at 60 db for
one second. The computer also interacted with the
stimulator such that six seconds after presentation of a
specific tone, a shock was administered. The presentation
of a low tone (usually 400 or 600 HZ) was not followed by a
shock. For the reward task, the computer produced one high
and one low tone. Six seconds after the high tone, the
screen produced a message stating how many dollars or
lottery tickets the subject had won so far and a picture of
a smiling face. Six seconds after the low tone, nothing
occurred.
Stimulus presentation and data storage was controlled
by customized application software. Equipment for recording
heartbeat (HR), skin conductance rate (SCR), corrugator
electromyography (CEMG), and zygomatic electromyography
(ZEMG) included a set of Colbourn Instruments data