Threat signals of pain modulate defensive responses in observers: development of an experimental paradigm Goubert, L.1*, PhD, Caes, L. 1, MSc, Uzieblo, K.2, PhD, De Ruddere1, L., MSc, Arnouts, A. 1, & Crombez, G.1, PhD 1 Department of Experimental-Clinical and Health Psychology, Ghent University, Belgium 2Lessius – University College ,Department of Applied Psychology, Antwerp, Belgium * Corresponding author: Liesbet.Goubert@UGent.be BACKGROUND AND AIMS RESULTS Central to understanding both the intrapersonal and interpersonal dimensions of pain is the recognition that pain serves as an archetypal sign of threat, not only to sufferers but also to observers. In this study, we investigated defensive responses in observers to threat signals of pain in others. An interpersonal observation paradigm was developed, adapted from Bradley et al., 2008. We expect that observers will demonstrate more defensive responses to signals predicting pain in the other than to safety signals. Furthermore, we expect that this effect will be most pronounced in observers with a high frequency of catastrophizing thoughts about pain and less pronounced in observers with high scores on psychopathy. In line with the expectations, OP reported more fear during pain signals (M=5.11, SD=2.46) than during safety signals (M=2.14, SD=2.09), t(35)=5.91, p< .01. A repeated measures ANOVA yielded a significant main effect of startle probe onset (F(1,35)=11.57, p<.01) and a significant signal x startle probe onset interaction, F(1,35)=14.11, p<.01. No significant main effect of signal was found, F(1,35)=.33. Startle blink reflexes were larger during pain signals compared to safety signals. The opposite pattern was found when the startle probe was administered immediately after the signal: OP demonstrated smaller startle reflexes following a pain signal compared with a safety signal. Further, the moderating effects of pain catastrophizing and psychopathy were examined. A significant catastrophizing x signal interaction was found, F(1,33)=4.78, p<.05. The 3-way catastrophizing x signal x startle probe onset interaction showed a trend toward significance, F(1,33)=3.45, p=.07. Parameter estimates showed a negative relationship between catastrophizing and startle blink reflexes after a safe signal, β=-.52 p<.01 (see Figure 3). Psychopathy also moderated the signal x startle probe onset interaction, F(1,34)=4.98, p<.05. A high score on psychopathy was related to smaller startle blink reflexes during pain signals (see Figure 4). METHOD Participants were 72 students (all female, M=18.89 years; SD=2.13) from Ghent University, Belgium. Each student was randomly allocated to the pain participant (PP) or observer participant (OP) role. The PP was exposed to electrocutaneous stimuli (ES) at tolerance level while being observed by the OP (see Figure 1 for an overview of the experimental set-up). Both participants were instructed that one coloured slide (blue or yellow; counterbalanced across participants) signalled that an electrocutaneous stimulus could be delivered to the PP (= “pain” condition; 24 trials; in ¼ of trials pain signal was followed by an ES), whereas no ES would be delivered when a differently coloured slide (yellow or blue) was presented (“safe” condition). After each yellow or blue signal an orange slide was shown, during which participants answered questions about pain and fear (see Figure 2). Psychophysiological responses (e.g. startle blink reflex) as well as self-reported catastrophic thoughts about pain and psychopathic characteristics were measured in observers. Startle probes (“white noise bursts”) were administered during (3s or 6s after signal onset) or after pain and safety signals (1s after signal offset). Figure 1: Overview of the experimental set-up Observing participant (OP) camera screen TV BIOPAC Observed participant (PP) shocker/ CONCLUSION The data suggest that anticipated pain in others elicits defensive reactivity in observers. In line with our hypotheses, observers demonstrated more defensive reactivity during signals predicting pain in the other participant than during safety signals. Less defensive reactivity in observers was found immediately following pain signals compared with safety signals. In line with our hypotheses, observers with more psychopathic traits were found to exhibit smaller defensive reactivity in anticipation of pain in the other participant (i.e., during a pain signal) compared to observers with less psychopathic traits. However, the findings on the moderating role of pain catastrophizing were more complex: high catastrophizing observers showed less defensive reactivity immediately after safety signals compared to low catastrophizing observers. The (preliminary) results provide indications for the usefulness of the paradigm in examining determinants of defensive responding to pain in others. Figure 2: Overview of 1 trial *5s 4s 10s 8s 3s 6s 1s REFERENCES Bradley, M.M., Silakowski, T. & Lang, P.J. Fear of pain and defensive activation. Pain 2008;137: 156 – 163. L. Caes is a PhD. Student of the Fund for Scientific Research - Flanders (Belgium)(F.W.O.).