After completing a puzzle in SudokuWorldTournament, you receive a "Brain Age" score – a fun yet scientifically-grounded estimate of your cognitive performance. But how do we calculate this number, and what does it actually measure?
In this article, we explain the cognitive science behind our Brain Age algorithm, the research that inspired it, and how you can use it to track your mental fitness over time.
What is Brain Age?
The concept of "Brain Age" was popularised by Nintendo's Brain Training games, developed in collaboration with neuroscientist Dr. Ryuta Kawashima. The idea is simple: cognitive abilities like processing speed and reasoning peak in early adulthood (around age 20-25) and gradually decline with age. By measuring these abilities, we can estimate a "brain age" that may differ from your chronological age.
Important: Brain Age is not a medical diagnosis or IQ test. It's a gamified metric designed to make cognitive training engaging and to help you track improvement over time. A "younger" brain age simply means you performed well on the specific cognitive tasks measured by Sudoku puzzles.
The Two Cognitive Pillars
Our Brain Age calculation is based on two well-established cognitive constructs from psychological research:
1. Processing Speed (40% weight)
What it measures: How quickly your brain can take in, understand, and respond to information. In Sudoku, this is reflected in how fast you can scan the board, identify patterns, and make decisions.
Scientific basis: Processing speed is one of the most reliable cognitive measures and is assessed in standardised tests like the WAIS-IV (Wechsler Adult Intelligence Scale). Research shows it peaks around age 18-25 and declines gradually thereafter (Salthouse, 1996).
How we measure it: We compare your solving time to an "optimal" time for each difficulty level, based on data from experienced players. Faster times indicate higher processing speed.
2. Fluid Intelligence / Reasoning Accuracy (60% weight)
What it measures: Your ability to think logically, identify patterns, and solve novel problems without relying on prior knowledge. This is the core cognitive skill tested by Sudoku.
Scientific basis: Fluid intelligence (Gf) is a central concept in cognitive psychology, distinct from crystallised intelligence (knowledge). It's measured by tests like Raven's Progressive Matrices and peaks around age 20-25 (Cattell, 1963; Horn & Cattell, 1967).
How we measure it: We track mistakes (indicating reasoning errors) and hints used (indicating need for external help). Fewer mistakes and hints indicate stronger reasoning ability.
The Algorithm Explained
Here's exactly how we calculate your Brain Age after each puzzle:
Step 1: Processing Speed Score (0-100)
timeRatio = actualTime / optimalTime
processingScore = max(0, 100 - (timeRatio - 1.0) × 50)
If you solve at optimal time or faster: 100 points
At 2× optimal time: 50 points
At 3× optimal time: 0 points
Step 2: Reasoning Accuracy Score (0-100)
errorPenalty = (mistakes / cellsToSolve) × 150
hintPenalty = (hints / cellsToSolve) × 75
reasoningScore = max(0, 100 - errorPenalty - hintPenalty)
Perfect solve (no mistakes, no hints): 100 points
Each mistake has a significant impact
Hints have a moderate impact
Step 3: Combined Cognitive Score
cognitiveScore = processingScore × 0.4 + reasoningScore × 0.6
We weight reasoning higher (60%) because Sudoku is primarily a logic puzzle. Processing speed matters, but accuracy matters more.
Step 4: Convert to Brain Age
brainAge = 80 - (cognitiveScore × 0.6) + difficultyAdjustment
Score 100 → Brain Age 20 (optimal)
Score 50 → Brain Age 50
Score 0 → Brain Age 80
Optimal Times by Difficulty
We calibrated optimal times based on data from experienced Sudoku players:
These times assume you're using logical techniques rather than guessing. Solving faster than optimal time gives you the maximum processing speed score – we don't penalise you for being exceptionally quick!
Difficulty Adjustments
Harder puzzles require more advanced cognitive skills. To account for this, we apply small adjustments to the final Brain Age:
Difficulty Bonuses
- Professor: -4 years (requires mastery of complex techniques)
- Expert: -3 years
- Hard: -2 years
- Medium/Daily: No adjustment
- Easy: +1 year (simpler cognitive demands)
This means solving a Professor-level puzzle perfectly will give you a younger Brain Age than solving an Easy puzzle perfectly – reflecting the greater cognitive challenge.
Why This Approach?
Grounded in Cognitive Science
Our algorithm isn't arbitrary – it's based on decades of research into cognitive ageing and intelligence. The two-factor model (processing speed + fluid intelligence) aligns with established theories like Cattell-Horn-Carroll (CHC) theory, which is the foundation of modern intelligence testing.
Sudoku as a Cognitive Task
Research has specifically examined Sudoku as a cognitive exercise. A 2019 study in the International Journal of Geriatric Psychiatry found that adults who regularly engaged in number puzzles like Sudoku showed cognitive function equivalent to people 8-10 years younger on certain measures (Brooker et al., 2019).
Meaningful Feedback
Unlike a simple score, Brain Age provides intuitive feedback. Everyone understands that a "younger" brain is better. This makes it easier to track progress and stay motivated to improve.
Interpreting Your Brain Age
🧒 20-25 years: Exceptional
You're performing at peak cognitive levels. Fast processing, accurate reasoning, minimal errors. This typically requires both speed and precision on harder difficulty levels.
🧑 26-35 years: Excellent
Sharp mind with quick thinking. You're solving efficiently with few mistakes. Most experienced players fall into this range on their best performances.
👨 36-45 years: Good
Solid cognitive performance. You might be taking a bit longer or making occasional errors, but your reasoning is sound. Room for improvement through practice.
🧔 46-55 years: Average
Typical performance for casual players. Consider focusing on learning techniques to reduce errors, or practice to improve speed.
👴 56+ years: Needs Training
Don't be discouraged! This often indicates unfamiliarity with Sudoku techniques rather than cognitive decline. Regular practice will quickly improve your Brain Age.
Tips to Improve Your Brain Age
🎯 Reduce Mistakes (Biggest Impact)
Mistakes heavily penalise your reasoning score. Take time to verify your logic before placing a number. Use pencil marks (notes) to track candidates and avoid errors.
⚡ Learn Techniques
Guessing is slow and error-prone. Learning techniques like Naked Pairs, Hidden Singles, and X-Wing allows you to solve faster AND more accurately. Our app teaches these techniques as you play.
🔄 Practice Regularly
Cognitive skills improve with practice. Daily Sudoku sessions of 15-30 minutes provide optimal training. Our Daily Challenge feature is perfect for building a consistent habit.
📈 Progressive Difficulty
Start with puzzles you can complete comfortably, then gradually increase difficulty. Struggling with puzzles far above your level leads to frustration and guessing – neither helps your Brain Age.
Scientific References
📚 Research Supporting Our Approach
- Salthouse, T. A. (1996). "The processing-speed theory of adult age differences in cognition." Psychological Review, 103(3), 403-428. – Foundational research on processing speed and cognitive ageing.
- Cattell, R. B. (1963). "Theory of fluid and crystallized intelligence: A critical experiment." Journal of Educational Psychology, 54(1), 1-22. – Original theory distinguishing fluid from crystallised intelligence.
- Horn, J. L., & Cattell, R. B. (1966). "Refinement and test of the theory of fluid and crystallized intelligence." Journal of Educational Psychology, 57(5), 253-270. – Research on how fluid intelligence changes with age.
- Brooker, H., et al. (2019). "The relationship between the frequency of number-puzzle use and baseline cognitive function in a large online sample of adults aged 50 and over." International Journal of Geriatric Psychiatry, 34(7), 932-940. – Direct evidence that number puzzles like Sudoku correlate with better cognitive function.
- Ferreira, N., et al. (2015). "Sudoku – A brain teaser: A systematic review of the neuroimaging literature." Dementia & Neuropsychologia, 9(4), 363-369. – Review of brain imaging studies during Sudoku solving.
- Kawashima, R. (2005). "Train Your Brain: 60 Days to a Better Brain." – The neuroscientist behind Nintendo's Brain Training games, which popularised the Brain Age concept.
- McGrew, K. S. (2009). "CHC theory and the human cognitive abilities project: Standing on the shoulders of the giants of psychometric intelligence research." Intelligence, 37(1), 1-10. – Overview of Cattell-Horn-Carroll theory underlying modern cognitive assessment.
Limitations & Disclaimers
Brain Age is for entertainment and motivation, not medical assessment.
- It measures performance on a specific task (Sudoku), not overall cognitive health
- Many factors affect performance: fatigue, distraction, familiarity with Sudoku
- A high Brain Age doesn't indicate cognitive impairment – it may just mean you're new to Sudoku
- If you have concerns about cognitive health, consult a healthcare professional
Start Training Your Brain Today
Ready to discover your Brain Age? Download SudokuWorldTournament and complete a puzzle to see your personalised cognitive assessment. Track your progress over time and watch your Brain Age improve as you master new techniques and sharpen your mental skills.
🎯 Key Takeaways
- Brain Age measures two cognitive abilities: processing speed (40%) and reasoning accuracy (60%)
- The algorithm is based on established cognitive science research
- Optimal Brain Age is 20; the scale goes up to 80
- Mistakes have the biggest negative impact – accuracy matters most
- Regular practice and learning techniques will improve your Brain Age
- Harder difficulties give bonus points, reflecting greater cognitive demands