Guides
Plain-language guides to what our tests and games measure, what the research says, and how to read your own result.
All guides
- What is a good reaction time?What researchers measure, why a phone and a laptop give the same person different scores, and what really moves your reaction time from one try to the next.20 October 2026 · 7 min read
- How many digits can you remember?The famous seven, plus or minus two, why newer research points to about four, and how grouping digits into chunks lets some people hold dozens of them.20 October 2026 · 7 min read
- How many things can you hold in visual memory?Why visual memory holds about four objects at a time, why a pattern is easier to hold than scattered squares, and how that plays out in our memory games.20 October 2026 · 7 min read
- What an online IQ test can and can't tell youHow professional IQ scores compare you with people your own age, why an online score isn't official, and what practice and the passing decades do to IQ.20 October 2026 · 7 min read
- Where does the idea of mental age come from?Mental age began as a way to place children at school, became the first IQ and was dropped for adults. Here is the history, and how our habit quiz uses it.20 October 2026 · 7 min read
- What the four letters of your type meanWhat each pair of letters in a 16-type result describes, where the idea comes from, what a close score means, and how types relate to personality traits.20 October 2026 · 7 min read
How these guides are written
Each guide starts from a question people ask after trying one of our tests or games, and answers it from published research. The sources are listed at the end of every guide, with links, so you can read them yourself.
We use AI tools to help draft the guides. Each one is checked against its sources and reviewed by Ali Hamza Nawaz before it goes live, and the date at the top shows when it was published or last updated.
The guides explain what scores mean in general. They can't tell you anything about your health, and they don't replace advice from a qualified professional.