Evaluating the Role of Expectations in Response to Caffeine Consumption: An RCT

Evaluating the Role of Expectations in Response to Caffeine Consumption: A Randomized Control Trial

The purpose of this project is to examine the effect of expectancy on mood and alertness after consumption of caffeine "treatment" or placebo "control" pill, given that participants know their probability for receiving the caffeine versus placebo pill. Participants will be randomly assigned a probability (ranging from 0-100%) of receiving caffeine vs. placebo, and this probability will be revealed to them before consumption of the assigned pill and subsequent cognitive testing. At the time of consumption, neither study staff administering the intervention nor participants will know for certain which pill is given to each participant. Pill assignment will depend on pre-determined randomization probabilities, which will be provided and assigned by the study statistician. By revealing participants' individual probability of receiving the caffeine pill, we will induce positive or negative expectancies regarding likelihood for receipt of the caffeine pill. These experimental manipulations will: 1) estimate the effect of expectancy on cognitive and affective outcomes, and 2) allow for a more direct estimate of the effect of the caffeine pill under real-world conditions than would a conventional randomized trial.

Inclusion Criteria:

• 18 years-old or older
• available to participate on the dates specified
• willing to take a caffeine or placebo pills at study session
• willingness to abstain from caffeine for 12 hours prior to study visit (8:30pm-8:30am)
• UAB employees or students with some college education (including current enrollment)

Exclusion Criteria:

• self-reported use of ADHD medication
• self-reported use of anxiety medication
• self-reported use of sleep medication
• self-reported use of nicotine products
• self-reported lactose intolerance
• self-reported uncorrected vision
• self-reported pregnancy or trying to become pregnant