Pre-existent expectancy effects in the relationship between caffeine and performance.

Area of Science:

• Cognitive Psychology
• Neuroscience
• Pharmacology

Background:

• Expectancy effects significantly influence subjective experiences and performance.
• Caffeine is a widely consumed psychoactive substance known for its stimulant properties.
• Understanding the interplay between caffeine's pharmacology and psychological expectations is crucial.

Purpose of the Study:

• To investigate how pre-existing expectations about caffeine content affect mood and vigilance.
• To determine the influence of perceived caffeine content versus actual caffeine load on performance.
• To examine the synergistic effects of caffeine's pharmacological action and expectancy.

Main Methods:

• A within-subjects design with 25 caffeine-deprived participants.
• A 2x2 factorial design manipulating caffeine load (caffeinated vs. decaffeinated coffee) and information accuracy (accurate vs. inaccurate).
• Assessment of mood and vigilance performance post-ingestion across four conditions.

Main Results:

• Caffeine significantly enhanced vigilance performance only when participants were accurately informed about its presence.
• Performance decreased when participants received decaffeinated coffee, irrespective of their expectations.
• When caffeine was administered but participants were misled to believe it was decaffeinated, performance was impaired to levels seen without caffeine.
• No clear effects on subjective mood were observed.

Conclusions:

• The pharmacological effects of caffeine on vigilance performance are modulated by expectancy.
• Accurate information about caffeine content is essential for caffeine to exert its performance-enhancing effects.
• Expectancy and caffeine's pharmacological action appear to act synergistically, highlighting the importance of psychological factors in substance effects.