Effects of expectation and caffeine on arousal, well-being, and reaction time

Schneider, Rainer; Grüner, Mauritz; Heiland, Alexandra; Keller, Martina; Kujanová, Zuzana; Peper, Martin; Riegl, Maximilian; Schmidt, Stefan; Volz, Petra; Walach, Harald (2006). Effects of expectation and caffeine on arousal, well-being, and reaction time. International journal of behavioral medicine, 13(4), pp. 330-9. New York, N.Y.: Springer 10.1207/s15327558ijbm1304_8

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The objective of this study is to determine the impact of expectation associated with placebo and caffeine ingestion. We used a three-armed, randomized, double-blind design. Two three-armed experiments varying instruction (true, false, control) investigated the role of expectations of changes in arousal (blood pressure, heart rate), subjective well-being, and reaction time (RT). In Experiment 1 (N = 45), decaffeinated coffee was administered, and expectations were produced in one group by making them believe they had ingested caffeinated coffee. In Experiment 2 (N = 45), caffeinated orange juice was given in both experimental groups, but only one was informed about the true content. In Experiment 1, a significant effect for subjective alertness was found in the placebo treatment compared to the control group. However, for RT and well-being no significant effects were found. In Experiment 2, no significant expectancy effects were found. Caffeine produced large effects for blood pressure in both treatments compared to the control group, but the effects were larger for the false information group. For subjective well-being (alertness, calmness), considerable but nonsignificant changes were found for correctly informed participants, indicating possible additivity of pharmacologic effect and expectations. The results tentatively indicate that placebo and expectancy effects primarily show through introspection.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > Service Sector > Institute of Legal Medicine > Forensic Psychiatric Services

UniBE Contributor:

Peper, Martin










Factscience Import

Date Deposited:

04 Oct 2013 14:51

Last Modified:

17 Mar 2015 21:55

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https://boris.unibe.ch/id/eprint/21744 (FactScience: 13504)

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