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

Abstract

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.

Expectation of having consumed caffeine can improve performance and mood

“…Expectation of having consumed caffeine by contrast, enhanced both overall accuracy and RT, regardless of the nature of the trial (congruent vs incongruent). These findings are in contrast to those reported by Schneider et al (2006) and Oei and Hartley (2005) who both found no effect of caffeine expectancy (i.e. whether participants had been told that they had been given caffeine or placebo) on RT.…”

“…This finding is consistent with previous studies suggesting that caffeine can alleviate depressed mood (Childs and de Wit, 2008). Consistent with other studies (Lotshaw et al, 1996;Schneider al al., 2006), expectancy effects were found for two of the four POMS sub-scales: depression-dejection and vigour-activity. Others, however, have found no consistent effects on self-reported mood (Elliman et al, 2010), which might reflect procedural differences.…”

“…However, two double-blind studies which manipulated expectancy through accurate, deceptive or ambiguous information, failed to replicate caffeine expectancy effects for physiological, psychological and cognitive variables (Walach, Schmidt, Bihr & Wiesch, 2001;Walach, Schmidt, Dirhold & Nosch, 2002). Other studies partially support caffeine expectancy effects; for instance, 4 Schneider et al, (2006) reported an expectancy effect for subjective alertness, but not for well-being or reaction time. Oei and Hartley (2005) took a slightly different approach and compared preexisting beliefs about caffeine's effects as well as manipulating the message concerning whether caffeine had been consumed using the balanced placebo design.…”

Acute Effects of Caffeine on Strength Performance in Trained and Untrained Individuals

“…This effect has also been previously imitated through placebo consumption [45]. Increased expectancy in a performance enhancing supplement can provide an athlete with greater arousal levels [46] which can in turn increase performance, especially in open, simple tasks [47]. However, this phenomenon does not explain the variation in results observed in the present study between trained and untrained individuals, suggesting the cause for disparity may be more complex.…”

Subjective and objective effects of coffee consumption — caffeine or expectations?

“…As caffeine had an impact on HRV-SDNN which reflects all cyclic components responsible for HR variability and had no impact on the more specific HF and LF/HF indices, no conclusions can be drawn regarding the autonomic background of this change. Although the hypertensive effect of caffeine is generally accepted (6,11,12,17,22,24,35), it was not demonstrated in all studies (17,37). HR-related results are also mixed.…”