Emotion and <strong>the</strong> post-auricular <strong>reflex</strong> 431 2000) and with motor deficits arising from Parkinson’s disease in humans (Heim et al., 2002). An alternative possibility is that increased post-auricular reactivity reflects enhanced orienting to <strong>the</strong> noise probe stimulus. Indeed, <strong>the</strong>re is evidence that unexpected noises can evoke observable movement <strong>of</strong> <strong>the</strong> post-auricular (pinna) muscle in primates in whom this muscle serves more than a vestigial function. Naturalistic observations <strong>of</strong> Hanuman langurs, a lower primate species, have revealed that in adult males, loud and surprising sounds yield brief (i.e., 0.2–0.3 s) movements <strong>of</strong> both <strong>the</strong> pinna and <strong>the</strong> head in <strong>the</strong> direction <strong>of</strong> <strong>the</strong> noise (Trivedi & Mohnot, 2002), suggesting that <strong>the</strong> pinna <strong>reflex</strong> serves an orienting function in this primate species. It may be that states <strong>of</strong> attentional engagement, such as those associated with viewing <strong>of</strong> pleasurable pictures, facilitate this phasic <strong>reflex</strong>ive orienting reaction. However, because pleasant and unpleasant pictures engage more attention than neutral (Lang et al., 1990, 1997), <strong>the</strong> predicted attentional pattern would have been one <strong>of</strong> <strong>postauricular</strong> <strong>reflex</strong> inhibition for both affective categories compared to neutral. Fur<strong>the</strong>rmore, juveniles and females <strong>of</strong> this species exhibit greater short-duration pinna movements primarily during play, feeding, and foraging for food (Trivedi & Mohnot, 2002), suggesting heightened responsiveness <strong>of</strong> this <strong>reflex</strong>ive system specifically during pleasurable activities. Never<strong>the</strong>less, <strong>the</strong>re is evidence that unpleasant pictures also engage attention (Lang et al., 1997), so it is possible that some types <strong>of</strong> aversive pictures might likewise facilitate <strong>the</strong> <strong>postauricular</strong> <strong>reflex</strong>. The current study focused on threat and physical attack pictures that tend to be perceived as fearful. Modulatory Ames, K. A., Merritt, N. P., Stout, K., & Hetrick, W. P. (2003). Differential effects <strong>of</strong> affective <strong>modulation</strong> on orbicularis and <strong>postauricular</strong> indices <strong>of</strong> startle. Psychophysiology, 40, S22. Anthony, B. J., & Graham, F. K. (1985). Blink <strong>reflex</strong> modification by selective attention: Evidence for <strong>the</strong> <strong>modulation</strong> <strong>of</strong> automatic processing. Biological Psychology, 21, 43–59. Benning, S. D., Patrick, C. J., Hicks, B., Blonigen, D., & Lang, A. R. (2001). Affective <strong>modulation</strong> <strong>of</strong> blink startle and post-auricular <strong>reflex</strong>es to noise probes. Psychophysiology, 38, S24. Bonnet, M., Bradley, M. M., Lang, P. J., & Requin, J. (1995). Modulation <strong>of</strong> spinal <strong>reflex</strong>es: Arousal, pleasure, action. Psychophysiology, 32, 367–372. Bradley, M. M., Codispoti, M., Cuthbert, B. N., & Lang, P. J. (2001). Emotion and motivation I: Defensive and appetitive reactions in picture processing. Emotion, 1, 276–298. Bradley, M. M., Cuthbert, B. N., & Lang, P. J. (1993). Emotion, novelty, and <strong>the</strong> startle <strong>reflex</strong>: Habituation in humans. Behavioral Neuroscience, 107, 970–980. Bradley, M. M., Drobes, D., & Lang, P. J. (1996). A probe for all reasons: Reflex and RTmeasures in perception. Psychophysiology, 33, S25. Braff, D. L., Geyer, M. A., & Swerdlow, N. R. (2001). Human studies <strong>of</strong> prepulse inhibition <strong>of</strong> startle: Normal subjects, patient groups, and pharmacological studies. Psychopharmacology, 156, 234–258. Cassella, J. V., & Davis, M. (1986). Habituation, prepulse inhibition, fear conditioning, and drug <strong>modulation</strong> <strong>of</strong> <strong>the</strong> acoustically elicited pinna <strong>reflex</strong> in rats. Behavioral Neuroscience, 100, 39–44. Cassella, J. V., Harty, P. T., & Davis, M. (1986). Fear conditioning, prepulse inhibition and drug <strong>modulation</strong> <strong>of</strong> a short latency startle response measured electromyographically from neck muscles in <strong>the</strong> rat. Physiology and Behavior, 36, 1187–1191. Center for <strong>the</strong> Study <strong>of</strong> Emotion and Attention [CSEA-NIMH]. (1999). The international affective picture system: Digitized photographs. Gainesville, FL: The Center for Research in Psychophysiology, University <strong>of</strong> Florida. REFERENCES effects may differ for o<strong>the</strong>r aversive contents, such as sadness, disgust, or mutilation pictures. It will also be important in future research to examine effects for o<strong>the</strong>r pleasurable picture contents (e.g., babies, animals, food). In addition, <strong>the</strong>re are o<strong>the</strong>r limitations <strong>of</strong> <strong>the</strong> current study that need to be addressed before firm conclusions can be advanced regarding <strong>the</strong> post-auricular <strong>reflex</strong> as an index <strong>of</strong> emotion. The current sample included only men; thus, it will be important to replicate <strong>the</strong>se findings in women. Fur<strong>the</strong>rmore, it will be important to assess <strong>modulation</strong> <strong>of</strong> <strong>the</strong> post-auricular <strong>reflex</strong> in emotional processing tasks o<strong>the</strong>r than picture viewing. A key question is whe<strong>the</strong>r potentiation <strong>of</strong> <strong>the</strong> post-auricular <strong>reflex</strong> would be observed in appetitive conditioning or reward anticipation contexts, as is true for startle in corresponding aversive paradigms (e.g., Hamm, Greenwald, Bradley, & Lang, 1993; Patrick & Berthot, 1995). Affirmative findings would lend support to <strong>the</strong> idea that <strong>the</strong> <strong>postauricular</strong> <strong>reflex</strong> is primed during appetitive states. Finally, in light <strong>of</strong> recent data indicating that hedonic valence and approach– withdrawal aspects <strong>of</strong> emotion are dissociable, it would be informative to assess whe<strong>the</strong>r <strong>the</strong> post-auricular <strong>reflex</strong> is enhanced or inhibited during a negatively valent approach state (e.g., anger; Harmon-Jones & Sigelman, 2001). 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