The Wonder Weeks - Frans X. Plooij & Hetty van de Rijt

The Wonder Weeks, by Frans X. Plooij and Hetty van de Rijt, reveals the science behind ten predictable mental development “leaps” that all babies experience in their first 20 months. These leaps mark major shifts in how babies perceive the world. Starting from basic sensory awareness to understanding sequences, relationships, and even early logic. Each leap unlocks new abilities but is often preceded by a period of fussiness, clinginess, and crankiness - what the authors call the “Three C’s.” The book helps parents recognize that these tough weeks are not signs of regression, but powerful progress happening inside the baby’s developing brain.

Using over three decades of research, The Wonder Weeks empowers parents to better understand their baby’s behaviors, reduce anxiety, and respond with empathy. By anticipating when a leap is coming, parents can prepare for disrupted sleep or mood changes, and respond with comfort, connection, and developmentally appropriate stimulation. With practical tools, milestone charts, and emotional reassurance, the book encourages parents to view challenging moments not as problems to solve, but as opportunities to support and celebrate their baby’s growth.