What 8 million scores reveal
Reaction time data from Human Benchmark shows a remarkably consistent pattern: cognitive processing speed peaks in the early 20s and then declines gradually — but the slope of decline is heavily modulated by lifestyle factors, especially physical activity and continued cognitive engagement. You can measure where you stand today with our Reaction Time test and compare your score against the global leaderboard.
Median reaction time by age — 8M scores
| Age group | Median RT (all) | Trained | Sedentary | Gap |
|---|---|---|---|---|
| 15–17 | 238ms | 230ms | 248ms | −18ms |
| 18–24 ← Peak | 222ms | 213ms | 234ms | −21ms |
| 25–29 | 228ms | 218ms | 240ms | −22ms |
| 30–39 | 242ms | 228ms | 255ms | −27ms |
| 40–49 | 262ms | 242ms | 275ms | −33ms |
| 50–59 | 280ms | 257ms | 300ms | −43ms |
| 60–69 | 305ms | 274ms | 322ms | −48ms |
Trained = self-reported regular aerobic exercise + 30+ HB sessions. Desktop users only (mobile excluded for hardware latency control).
Why cognitive speed declines with age
Age-related slowing is not a single process — it reflects multiple simultaneous changes in the nervous system that compound over decades.
Myelin degradation
Myelin — the fatty sheath insulating nerve fibers — thins with age, reducing neural conduction velocity. White matter integrity, measured by diffusion tensor imaging, correlates strongly with simple reaction time across the lifespan. This process begins in the 30s and accelerates after 60.
Dopaminergic decline
Dopamine receptor density in the striatum — critical for motor initiation and response speed — declines approximately 6–7% per decade after age 20. Dopamine signaling affects both how quickly the brain commits to a response and how accurately it times motor output.
Reduced processing speed (g factor)
General cognitive processing speed — sometimes called the "g factor" — declines with age in a way that affects virtually all timed cognitive tasks. Even simple button-press tasks slow down, suggesting a system-wide neural efficiency decline rather than domain-specific losses. Our Processing Speed test measures this directly.
Working memory bottlenecks
In choice reaction time tasks — where the response depends on what was just shown — working memory capacity increasingly becomes the bottleneck with age. Older adults maintain accuracy but slow down considerably on multi-choice tasks, especially under time pressure.
What you can control: modifiable factors
1. Aerobic exercise
Strongest evidenceRegular aerobic exercise is the single most evidence-supported intervention for preserving cognitive speed across the lifespan. Long-term exercisers show reaction times 15–40ms faster than sedentary peers at every age over 40. The mechanisms include increased BDNF (brain-derived neurotrophic factor), better cardiovascular perfusion of the brain, and preserved white matter integrity. See the full evidence in our Brain Health guide.
2. Sleep quality and duration
High evidenceChronically sleeping less than 7 hours accelerates cognitive aging. A 2021 Nature Communications study (n=500,000) found that consistently sleeping 6 hours or less is associated with 30% higher dementia risk at age 70. For reaction time specifically: sleep quality in your 40s and 50s strongly predicts reaction time in your 60s and 70s.
3. Continued skill practice
Moderate evidenceDomain-specific practice maintains cognitive speed in that domain better than general "brain training." Musicians, surgeons, and competitive gamers maintain above-average reaction times well into their 50s and 60s due to continued skill practice. The key is high-frequency, feedback-rich practice — not passive engagement.
The good news: decline is not destiny
The most important finding from our data is the magnitude of the training gap. A trained 60-year-old consistently outperforms a sedentary 35-year-old. The absolute rate of decline matters far less than whether you maintain the behaviors that preserve cognitive speed.
What the data shows about compensatory mechanisms
- →Older adults compensate for slower raw processing with superior pattern recognition and anticipation
- →Domain expertise compresses reaction time variance — experts make fewer slow errors even as mean RT increases
- →Strategy adoption (positioning, prediction, context reading) partially offsets processing speed losses in real-world tasks
Bottom line
Aerobic exercise started at any age produces measurable improvements in cognitive speed within 6–12 weeks. Starting at 50 is dramatically better than not starting at all — you will not recapture 24-year-old speed, but you can maintain the function of someone a decade younger.
Where do you sit for your age?
Compare your reaction time to the average for your age group. Return in 30 days of aerobic training to see the change.
Take the Reaction Time test