Se. Andrews et al., EFFECTS OF CAFFEINE AND CAFFEINE-ASSOCIATED STIMULI ON THE HUMAN STARTLE EYEBLINK REFLEX, Pharmacology, biochemistry and behavior, 59(1), 1998, pp. 39-44
An experiment was performed (n = 19) that investigated the effect of c
affeine and expectancy of caffeine on the eyeblink component of the st
artle reflex. Nineteen habitual caffeine users received caffeinated co
ffee, caffeinated juice, decaffeinated coffee, or decaffeinated juice
in four sessions spaced 1 week apart. Twenty-five to 30 min after inge
stion of the liquid, 30 acoustic startle stimuli were presented. The r
esults showed that caffeine increased startle eyeblink amplitude. Star
tle reflex onset latency was significantly longer in the decaffeinated
coffee condition than in the other three conditions. This may have be
en due to the activation of a compensatory slowing of the reflex by th
e anticipation of caffeine, a slowing that was then overridden by caff
eine speeding the response. (C) 1998 Elsevier Science Inc.