Effects of Caffeine on Chess Performance and Cognitive Function in Professional Chess Players

This randomized double-blind crossover trial will evaluate the effects of moderate caffeine intake on cognitive and competitive performance in professional chess players. Twelve FIDE-rated chess players will complete two experimental conditions in randomized order: caffeinated coffee and decaffeinated coffee placebo. During each visit, participants will complete standardized cognitive assessments and a tournament-style chess game under controlled laboratory conditions.

Primary outcomes will include objective chess performance metrics derived from chess engine analysis, including move accuracy, centipawn loss, error rates, and time management. Secondary outcomes will include cognitive test performance, tactical reaction time, and self-reported alertness and fatigue. Chess games will be analyzed using standardized software-based evaluation methods.

The crossover design allows each participant to serve as their own control, minimizing variability related to individual differences in skill level, caffeine tolerance, and playing style. The study aims to determine whether caffeine enhances sustained attention, decision-making, and competitive chess performance during prolonged gameplay. Findings may provide insight into nutritional strategies for cognitive performance optimization in mentally demanding competitive environments.

• Caffeinated Coffee (Dietary supplement): Black caffeinated coffee prepared from 15 g of ground coffee brewed in 200 g of water, providing approximately 100 mg of caffeine. The beverage will be consumed approximately 30 minutes before cognitive testing and tournament-style chess gameplay.
• Decaffeinated Coffee Placebo (Dietary supplement): Black decaffeinated coffee prepared from the same batch of coffee beans and matched for taste and appearance to the caffeinated condition. The beverage will be consumed approximately 30 minutes before cognitive testing and tournament-style chess gameplay.

Primary outcomes

• Chess Performance Accuracy [30 minutes after beverage consumption through completion of the tournament-style chess game at each experimental visit.]: Chess performance accuracy will be assessed using engine-based analysis of tournament-style chess games. The primary reported metric will be average centipawn loss per move, with lower values indicating better chess performance accuracy.

Secondary outcomes

• Puzzle Rush Correct Responses [Approximately 30 minutes after beverage consumption at each experimental visit.]: Tactical accuracy will be assessed using the 3-minute Puzzle Rush task on Chess.com. The outcome will be the total number of correctly solved tactical puzzles, with higher scores indicating better tactical accuracy.
• Puzzle Rush Response Speed [Approximately 30 minutes after beverage consumption at each experimental visit.]: Response speed will be assessed using the 3-minute Puzzle Rush task on Chess.com. The outcome will be average response time per puzzle, with lower values indicating faster response speed.
• Stroop Test Performance [Before gameplay and immediately after gameplay at each experimental visit.]: Selective attention will be assessed using the Stroop Test. The outcome will be the change in Stroop Test completion time from before gameplay to immediately after gameplay, with lower completion time indicating better performance.
• Trail Making Test Performance [Before gameplay and immediately after gameplay at each experimental visit.]: Cognitive flexibility and processing speed will be assessed using the Trail Making Test. The outcome will be the change in Trail Making Test completion time from before gameplay to immediately after gameplay, with lower completion time indicating better performance.
• Self-Reported Alertness [Pre-game and immediately post-game at each experimental visit.]: Self-reported alertness will be assessed using a study-specific visual analog questionnaire. Higher scores will indicate greater perceived alertness.
• Self-Reported Mental Fatigue [Pre-game and immediately post-game at each experimental visit.]: Self-reported mental fatigue will be assessed using a study-specific visual analog questionnaire. Higher scores will indicate greater perceived mental fatigue.
• Average Time Per Move [From the start of the tournament-style chess game until game completion, assessed over approximately 3 to 4 hours at each experimental visit.]: Chess time management will be assessed as the average time used per move during each tournament-style chess game. This value will be calculated from the total game time divided by the number of moves completed by the participant.

Sex: All, ages: 18 Years to 50 Years, accepts healthy volunteers

Inclusion Criteria:

* Male and female professional chess players aged 18-50 years
* Current Fédération Internationale des Échecs (FIDE) standard rating between 2300 and 2600 Elo, or achievement of a standard FIDE rating within this range during the previous 12 months
* Habitual caffeine consumers consuming ≤2 cups of coffee per day
* Willingness to comply with all study procedures and study visits
* Ability to provide written informed consent

Exclusion Criteria:

* Non-caffeine users
* Habitual caffeine intake exceeding 2 cups of coffee per day
* Cardiovascular disorders
* Metabolic disorders
* Psychiatric disorders
* Pregnancy or breastfeeding
* Current smoking
* Shift workers
* Use of psychoactive medications
* Participation in another clinical trial within the previous 3 months
* Known allergy or intolerance to milk proteins, dairy products, or soy
* Known red-green color blindness or other color vision deficiencies that may interfere with Stroop Test performance

• Hossein Rafiei, PhD, Principal investigator, St. Louis University