Effects of nicotine on neurocognitive performance have been shown but are influenced by nonpharmacological expectancies in smokers, whereas there is little knowledge about expectancy effects in nonsmokers. A half balanced placebo design provides no drug but only placebo and tests the effects of expectations elicited by the information that nicotine was given. Sixty-four healthy participants balanced for smoking status and sex were told that a chewing gum may contain either nicotine or is a placebo in a double-blinded and randomized fashion. One hour later and immediately before neurocognitive function testing (Parametric Go/No-Go task) they were informed--balanced for smoking status and sex--that they belong to the nicotine or to the placebo group. Reaction times of Go responses (RT) and the number of false No-Go responses were analyzed. A significant interaction of all three factors (information, smoking status, sex) was found, indicating that the information to have received nicotine compared with placebo shortened RTs in female smokers but increased it in female nonsmokers, whereas results in men are in part reversed. No effects on No-Go errors were found, and beliefs about nicotine effects had no influence on results. Therefore, the known effects of nicotine on RTs could be influenced by stimulus expectancy not only in smokers but also in nonsmokers. Furthermore, previous results on sex-specific responsiveness to nicotine instructions are supported.
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