Suggested reading path
If this is your first visit, start with the limits of browser-based measurement. Then read about sleep, caffeine, and practice plateaus to understand why the same person can get different scores across days and devices.
- The Age Curve of Cognitive Speed — Does It Peak in Your 20s?
How reaction time and cognitive speed change with age, explained as a gentle curve. Covers practice effects, individual differences, and why one score isn't aging.
- Browser Tests vs. Lab Tests — What's Different
How precisely do lab and browser measurements of reaction time differ? We break down refresh rate, input latency, JS timer precision, and why relative comparison matters.
- How Many Milliseconds Does Caffeine Actually Shave Off?
How much, when, and for whom caffeine improves reaction time, based on research evidence. Covers tolerance, timing, and limits with a hands-on experiment idea.
- How Chunking Stretches Your Memory Capacity
Working memory holds information in chunks. We explain why chunking lets the same capacity hold more, with everyday examples and the chess master case.
- The Digit Span Test — A Measurement Since 1887
The digit span test dates back to Jacobs in 1887 and lives on in the WAIS. We cover its forward/backward variants, average scores, and how this site's game differs.
- The Evidence for Aerobic Exercise Boosting Cognitive Speed
Meta-analyses show regular aerobic exercise modestly improves executive function and processing speed. We review the BDNF and cerebral blood flow mechanisms.
- How Hand-Eye Coordination Develops — and How We Measure It
Hand-eye coordination develops from infancy through adolescence and keeps improving with practice. We review Fitts' law and how the aim game measures it.
- Why Korean Letters Are Harder to Remember Than Digits
Digits are 10 symbols; Korean jamo are 40. We look at the visual complexity of combinatory letters, the two-sided nature of chunking, and why a Korean-letter memory task differs from a digit task.
- Larks vs. Owls: When Is Your Reaction Fastest?
How circadian rhythm and chronotype shape reaction time. Covers sleep inertia, time-of-day effects, and the conditions for a fair measurement.
- Does Multitasking Actually Exist?
Cognitive science says human 'simultaneous' processing is really rapid task switching. We cover switching cost, working memory's role, real-life risks, and the edge of single-tasking.
- The Reaction-Time Plateau — Where Practice Stops Helping
Why simple reaction time saturates quickly with practice, why complex tasks plateau later, and how environmental factors end up mattering more than reps.
- Pro Gamer Reaction Times — What the Numbers Actually Look Like
Pro esports players' reaction times split into simple RT and choice RT. We look at public benchmarks and where the real gap with non-pros actually comes from.
- Reaction Time vs. Reflex — What's the Difference?
Reflexes and reaction time look similar but involve different brain processes and different numbers. We clarify why 'good reflexes' usually means reaction time.
- How Monitor Refresh Rate Skews Reaction-Time Tests
Refresh rate and frame delay add random latency to reaction-time tests. We break down the numbers and explain what makes a fair comparison between devices.
- How Sleep Loss Slows Your Reaction Time
Sleep deprivation has an immediate effect on reaction time. We break down the sleep-medicine research, sleep debt, and how recovery actually works.
- What Stress and Cortisol Do to Working Memory
Mild stress sharpens arousal, but chronic stress and cortisol erode working memory. We review the Yerkes-Dodson curve and prefrontal-hippocampus findings.
- The Suneat Generation — Mental Math Before Calculators
Korean classrooms from the 1980s to the early 2000s emphasized mental math and multiplication-table fluency over calculators. We trace how number-sense automation shaped a generation.
- Why '7±2' Is a Misleading Rule of Thumb for Working Memory
The famous '7±2' working memory rule is widely misquoted. We trace its origin to Miller's 1956 paper and compare it with modern estimates like Cowan's 4±1.