544 Pre Post Difference Discussion Table 5 Pre-, post- and difference scores on P2 in all conditions (n=20, mean±SEM) Control 19.5±2.0 19.5±2.3 0.0±0.6 Placebo 20.0±1.9 17.1±1.7 −2.9±1.0 Caffeine 19.2±2.2 17.2±2.0 −2.0±1.0 Active placebo 19.3±2.0 16.7±1.8 −2.6±1.1 The hypothesis that side effects of caffeine can enhance expectancies and the placebo response was tested. Four milligrammes per kilogramme of caffeine increased arousal compared to 0 mg/kg, but did not enhance expectancies of drug efficacy. Information that a painkiller had been administered did not reduce pain compared to information that no drug had been administered. However, a placebo response on P2 amplitude was observed in males. Four milligrammes per kilogramme of caffeine reduced pain compared to 0 mg/kg. The mean pain relief of caffeine administered with information that it was a painkiller was not significantly different from caffeine administered with “no drug” information. However, the pain relieving effect of caffeine was disrupted after about 4 min of the posttest in the caffeine condition, but increased steadily over time in the active placebo condition, showing that information modulated the analgesic effect of caffeine. The modulation of caffeine’s analgesic effect by information was partly due to expectancies of pain relief, but was not related to the arousing effects of caffeine. Information Information that an over-the-counter painkiller had been administered did not reduce reported pain compared to information that no drug had been administered. This is in line with Colloca et al. (2008) who found that an inert cream administered with verbal suggestions that it was analgesic had no effect on reported pain. The results of the current study showed that subjects given drug information were relatively uncertain about the effectiveness of the painkiller. Probably, subjects were not convinced by the verbal information and consequently expectancies about pain relief were low. However, pain reduction in the Fig. 3 N2 amplitudes. a Mean N2 amplitudes (± SEM) across b conditions. There was a tendency towards a larger reduction in N2 amplitude after 4 mg/kg caffeine compared to 0 mg. b Reduction in N2 amplitude correlated with reduction in pain in the placebo condition (r=.48, p=.03). c Reduction in N2 amplitude correlated with reduction in pain in the active placebo condition (r=.54, p=.01) Psychopharmacology (2011) 215:537–548