Evidence of conditioned cognitive and mood effects of caffeine in humans using a differential conditioning paradigm

Caffeine is a well-known psychostimulant drug, capable of facilitating psychomotor and cognitive performance, improving mood and attenuating fatigue. Moreover, caffeine-related stimuli (e.g. smell and/or taste of coffee) have been associated with increases in physiological and subjective arousal and improvements in vigilance performance. These effects may have been due to classical conditioning but may also have been potentiated by expectancy due to the use of commonly consumed caffeinated beverages. The current study examined the role of classical conditioning, by examining whether a novel caffeine-paired context could acquire the ability to elicit caffeine-like facilitation on performance and mood. A differential conditioned paradigm was used in which one context was paired with caffeine ingestion (400 mg in a capsule) and a second context was paired with placebo. After four pairings in each condition, a test of conditioning was conducted in which placebo was administered in each context. The findings demonstrated significantly faster reaction time performance after placebo in the context previously paired with caffeine ingestion compared to the context previously paired with placebo. Furthermore, these conditioned effects were acquired quickly, after just two caffeine-context pairings and were acquired despite a reported absence of CS-US contingency awareness.