Expectancy effects in caffeine research.
The impact of expectancy on the experience of caffeine-related symptoms was investigated by randomly assigning subjects to an expectancy or nonexpectancy instructional condition. Subjects were administered the State-Trait Anxiety Inventory and a Symptom Questionnaire prior to and 45 minutes after receiving their designated instructional set and ingesting a cellulose-filled gelatin capsule which ostensibly was filled with caffeine. Results revealed that a significant expectancy effect existed on five Symptom Questionnaire items.
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