The human startle reflex is reliably modulated by the affective valenc
e of foreground pictures, with larger reflexes elicited when viewing u
npleasant relative to pleasant scenes. If this modulation is due to pr
iming of the defensive startle reflex by an aversive foreground, a dif
ferent pattern should occur for a reflex that is not inherently defens
ive in nature. In the current study, affective modulation was investig
ated using the spinal tendinous (T) reflex, which is well documented a
s sensitive to differences in arousal and is involved in actions that
are both appetitively and defensively motivated. As such, T reflexes e
licited during unpleasant pictures were not expected to be augmented r
elative to those elicited in the context of pleasant pictures. Results
showed that T reflexes were facilitated during processing of arousing
stimuli-either pleasant or unpleasant relative to low-arousal neutral
materials. These effects of emotional stimuli on T-reflex amplitude a
re consistent with the hypothesis that motivational priming underlies
affective reflex modulation.