【DIGEST】読書で本当に頭は良くなるのか？／長時間読書は逆効果／理科・算数・英語も成績が良くなる理由／読書は１日何分がベストかを徹底解説

Educational psychologist Keisuke Iihara explains why reading boosts all subjects but daily sessions over 2 hours can reverse the effect.

• National academic survey data shows students who love reading score 17 points higher in Japanese language tests than non-readers, across both 6th grade and 9th grade cohorts.\n- Reading boosts a broad range: logical thinking, critical thinking, creativity, empathy, vocabulary, and overall academic performance — no other single activity shows this breadth of effect.\n- Students reading 2+ hours daily show an inverted-U effect: math and science scores drop, likely because extended sessions drift toward easy or repetitive content (re-reading manga, etc.) rather than challenging material.\n- Heavy reading also crowds out other high-value activities — sports, parent conversation, structured study — all of which independently lift academic outcomes.\n- Reading comprehension measured at age 8–9 predicts math score growth by age 13–14, specifically on word problems, not pure calculation; vocabulary is the mechanism.\n- Two causal paths exist: reading directly builds language ability and academic skill, but homes with more books also correlate with higher income and tutoring access, so family environment is a confound.\n- For modern readers, Iihara recommends 30–60 minutes per day of real books for chosen titles; AI summaries are acceptable for reference texts like Capital but cannot replace the experiential value of narrative reading.

2026-04-25 · Watch on YouTube