Conditions: Caffeine Affect Cognitive Ability, General Mood
Keywords: Vigilance Mood Randomized Controlled Trial Probability
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 205
Healthy volunteers: yes

Brief summary:
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.

Detailed description:

Arms:
arm 1: One-time treatment with 200mg caffeine pill arm 2: One-time treatment with lactose-based placebo pill

Interventions: intervention 1: Caffeine intervention 2: Placebo
Intervention descriptions: intervention 1: 200mg delivered as pill; one-time dose intervention 2: Lactose-based pill; one-time dose

Protocol document: