Does Reading Actually Make You Smarter? The Evidence

Educational psychologist Keisuke Iihara breaks down the causal link between reading and academic performance using research data.

• On Japan’s national academic achievement tests, children who enjoy reading score roughly 17 percentage points higher in Japanese language on average
• Data shows an “inverse effect”: academic performance drops when reading time exceeds two hours a day
• Beyond two hours, reading tends to be low-quality or repetitive — and the causal direction likely reverses
• Reading comprehension at age 9 predicts math growth at age 14, especially on word problems
• Reading benefits science and math because language ability is the foundation for all subjects
• Reading actual books builds a feel for tone and context that AI summaries do not
• The modern approach: 30–60 minutes a day, focused on a small number of books read carefully

2026-04-25 · Watch on YouTube

Japanese page: 読書で本当に頭は良くなるのか？科学的根拠