Figure 1

Study Design. The Gene + group were told they had tested positive for a gene associated with heightened caffeine withdrawal symptoms. The Gene− group were told they had tested negative for this gene. The Told Caffeine group were told they were receiving caffeinated coffee. The Told Decaf group was told truthfully that they were receiving decaffeinated coffee. Baseline, Pre-Beverage and Post-Beverage tests were, in order: 1) Blood Pressure; 2) Score on the Caffeine Withdrawal Symptom Questionnaire (CWSQ; Juliano et al., 2012); 3) Score on the RVIP task, a test of concentration.