Expectation of having consumed caffeine can improve performance and mood

Area of Science:

• Neuroscience
• Psychology
• Pharmacology

Background:

• Caffeine is a widely consumed psychoactive stimulant.
• Its effects on cognitive functions like attention and mood are well-documented.
• The role of expectation in modulating the effects of substances is an area of growing interest.

Purpose of the Study:

• To investigate the independent and combined effects of caffeine and the expectation of caffeine consumption on attention, reward responsivity, and mood.
• To differentiate between the pharmacological effects of caffeine and the psychological effects of expectation.

Main Methods:

• A double-blind, placebo-controlled study involving 88 participants.
• Participants were randomly assigned to four conditions based on drink type (caffeinated/decaffeinated coffee) and expectancy (told caffeinated/told decaffeinated).
• Measures included attention, psychomotor speed, reward responsivity, and mood assessments.

Main Results:

• Both actual caffeine consumption and the expectation of having consumed caffeine significantly improved attention and psychomotor speed.
• Expectation alone enhanced self-reported vigour and reward responsivity.
• While self-reported depression increased post-consumption for all, it was less pronounced in participants who received or expected caffeine.

Conclusions:

• Caffeine significantly impacts attention and mood.
• The expectation of caffeine consumption can independently influence mood and performance, particularly enhancing vigour and reward sensitivity.
• No synergistic effect was observed between caffeine and expectation, suggesting distinct pathways for their influence.