Meta-Analysis

The Age When Parents Want to Drop the Nap Is Exactly When the Nap Helps Most

A 2025 meta-analysis pooling 27 studies and 67 effect sizes found that naps boost declarative memory in early childhood — and the effect size is largest, surprisingly, in 3- to 5-year-olds, exactly the age when parents most often consider dropping the nap.

"Just Let Them Play a Lot, Right?" — A Meta-Analysis Says the Quality of Play Matters More Than the Quantity

A meta-analysis of 34 studies and 188 effect sizes confirms that pretend play is linked to social competence in young children — but the link is stronger when researchers measured the richness of play rather than its duration.

Data from 150,000 Children Speaks — Does Father Involvement Actually Matter?

A meta-analysis of 65 studies and over 150,000 children finds that father involvement has a real, lasting effect on social-emotional development — and warmth matters more than time.