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Related Experiment Video

Updated: Jun 14, 2026

Experimental Protocol for Examining Behavioral Response Profiles in Larval Fish: Application to the Neuro-stimulant Caffeine

Experimental Protocol for Examining Behavioral Response Profiles in Larval Fish: Application to the Neuro-stimulant Caffeine

Published on: July 24, 2018

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

Nicola A Elliman¹, Jennifer Ash, Michael W Green

¹Nutrition and Behaviour Laboratory, Psychology Institute, School of Life and Health Sciences, Aston University, Birmingham, UK. n.elliman@aston.ac.uk

|April 13, 2010

Summary

This summary is machine-generated.

Caffeine enhances vigilance performance but only when participants expect it. Believing coffee is decaffeinated negates caffeine's positive effects on performance, regardless of actual caffeine content.

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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.